Phytochemistry, Pharmacological Potential and Industrial Applications of Ricinus communis L.: A Review

1. Introduction

Medicinal plants are the oldest known form of treatment, used for millennia in traditional medicine across numerous nations globally. The experiential understanding of their therapeutic benefits has been passed down through generations within human societies [1]. Approximately 10% of all vascular plants are used for medicinal purposes with estimates suggesting that there are between 350 000 and 500 000 species of these plants [1]. In many parts of the world, 70-80% of the population relies on the use of medicinal plants, herbal remedies, or other plant-derived preparations for the empirical treatment of a range of ailments, attributed to the effectiveness, cultural tradition, and affordability of these botanical resources [2].

Significant progress has been made in the pharmacological and industrial applications of R. communis particularly in validating its traditional medicinal uses and expanding its industrial value chain. Pharmacologically, extracts and isolated compounds from R. communis have demonstrated antimicrobial, anti-inflammatory, antioxidant, hepatoprotective, antidiabetic, and anticancer activities in some studies, supporting many ethnomedicinal claims [3]. Castor oil remains widely used as a laxative and is increasingly investigated for drug delivery systems and antimicrobial formulations [4]. Industrially, castor oil has gained importance as a renewable feedstock to produce biodiesel, biopolymers, lubricants, surfactants, cosmetics, and nylon-11, contributing to sustainable and bio-based industrial development [5]. Despite several published reviews, a comprehensive and updated synthesis integrating pharmacological evidence, traditional knowledge, toxicity considerations, and emerging industrial innovations remains necessary. Previous reviews have concentrated on specific aspects of R. communis, such as its phytochemistry, ethnobotanical uses, or industrial applications, thereby indicating the need for a more comprehensive and up-to-date evaluation that integrates its biological activities, methodological approaches, and potential for practical application. A unified review would connect these fields, address both safety and effectiveness as well as industrial applicability, and highlight avenues future for research aimed at responsible utilization and commercializing R. communis. Therefore, this review seeks to consolidate existing knowledge on the plant’s chemical composition and bioactive compounds and assess the breadth of its biological activities by examining the range of pharmacological activities investigated, the diversity of experimental models used, and the consistency and quality of findings across different studies as well as its industrial significance.

2. Botanical Description and Geographic Distribution of R. communis L.

R. communis, commonly known as the castor bean or castor oil plant, is a monoecious shrub or small tree belonging to the family Euphorbiaceae. It is typically 2–5 m tall but can grow up to 10 m under favourable conditions, particularly in warm tropical and subtropical climates with high temperatures (20–30 °C), well-drained fertile soils, adequate moisture, and frost-free environments [6]. The plant has smooth, often glaucous stems that may appear green, red, or purplish depending on the cultivar. Its leaves are alternate, large, and palmately lobed, usually with 5–12 lobes, borne on long petioles. Leaf colour varies among varieties, ranging from bright green to deep purple [7]. The inflorescences are terminal or axillary racemes bearing both male and female flowers on the same plant [8]. The male flowers, found on the lower part of the inflorescence, are numerous and contain many stamens, whereas the female flowers, positioned above, have a three-celled ovary and conspicuous red stigmas. The fruit is a spiny, three-lobed capsule containing large, oval, mottled seeds rich in castor oil [9]. These seeds contain the toxic protein ricin; however, the extracted oil itself is non-toxic because ricin is water-soluble and does not enter the oil during extraction [10]. The plant is noted for its adaptability to a wide range of soils and climates, as well as its rapid growth and phenotypic variability. R. communis is native to tropical Africa, particularly the northeastern and eastern regions of the continent [11]. It has, however, been widely naturalised and cultivated around the world, making its exact native range uncertain. Today, it is distributed throughout tropical and subtropical regions and is commercially grown for industrial oil production in countries such as Mexico, India, Brazil, Argentina, China, Mozambique and United States [12]. R. communis is also widely distributed in South Africa where it occurs as both cultivated and naturalized species [13]. It is abundant in warmer provinces such as Limpopo, Eastern Cape, Mpumalanga and KwaZulu Natal [14]. The plant commonly occurs in disturbed habitats, including roadsides, riverbanks, and wastelands, where it often escapes cultivation and establishes wild populations. In some regions, it behaves as an invasive species, forming dense stands that suppress native vegetation. Molecular and morphological studies indicate considerable genetic diversity among global populations, suggesting broad ecological adaptability [15,16].

3. Cultivars of R. communis L.

R. communis is classified as a monotypic species, indicating that the Ricinus genus comprises only of a single species [17]. Across its many cultivars like Impala, Carmencita, Gibsonii, Red Spire, New Zealand Purple, and Zanzibarensis the horticultural differences (height, leaf colour, stem pigmentation) reflect ornamental selection [18]. These cultivars often thrive under similar favourable growth conditions: warm temperatures (ideally 20–25 °C), full sun, fertile and well-drained soils, and regular moisture during establishment, with protection from frost in colder regions [19].For instance, dwarf forms like Impala or New Zealand Purple are well suited to sunny beds or large containers, while tall, architectural cultivars such as Red Spire or Zanzibarensis lend themselves to spacious subtropical landscapes [20,21].

3.1. Carmencita Bright Red

Carmencita bright red (Figure 1) is a striking ornamental cultivar of R. communis, widely cultivated in Spain and other parts of Europe for its vivid coloration and bold architectural form. It is characterized by large, deeply lobed palmate leaves that display a bronze to burgundy-red hue, complemented by prominent red female flower spikes and seed pods. When grown as an annual, it typically reaches a height of 1.5–2 m, making it suitable for garden borders and landscape focal points [22,23,24].

3.2. Gibsonii

Gibsonii (Figure 2) is another visually dramatic cultivar, commonly reported in India, where it is appreciated for its vigorous growth and ornamental foliage. This variety exhibits dark, reddish-metallic leaves with pronounced red veins, along with red stems and bright scarlet seed heads. It has a tall and robust growth habit, often reaching substantial heights within a single growing season, which enhances its use as a statement plant in gardens and landscapes [26].

3.3. Zanzibarensis

Zanzibarensis (Figure 3) originating from Tanzania (particularly the Zanzibar region), is notable for its exceptional size and lush appearance and is now widely distributed across several other regions due to its adaptability, rapid growth, and ornamental appeal. Beyond East Africa, this cultivar is commonly cultivated in other parts of Africa, including South Africa, where it thrives in warm, subtropical climates and is frequently used in ornamental landscaping and garden displays. This cultivar can grow between 2–3 m as an annual and is distinguished by its very large mid-green leaves, which may reach up to 50 cm in length, featuring characteristic whitish midribs. Its green stems and expansive foliage contribute to its reputation as one of the largest and most vigorous castor bean varieties [28,29].

3.4. New Zealand Purple

New Zealand Purple (Figure 4) is predominantly cultivated in New Zealand and is valued for its rich, ornamental coloration. The plant displays deep plum to purple-tinged leaves and stems, creating a dramatic visual contrast in gardens. Its seed pods are also purple but gradually turn red as they mature. Typically growing to around 1.5 m as an annual, this cultivar is favoured for decorative landscaping due to its consistent coloration and moderate size [31,32].

3.5. Impala

Impala (Figure 5) is a compact cultivar commonly grown in South Africa and similar subtropical environments, where space-efficient ornamental plants are preferred. It reaches a height of approximately 1.2 m and is characterized by reddish-purple to bronze foliage and stems, with the most intense coloration observed in young shoots. Due to its smaller stature, Impala is particularly suitable for container planting and small garden spaces, offering both aesthetic appeal and practicality [34,35].

4. Phytochemical Profile of R. communis L.

The phytochemistry of R. communis has been widely investigated and the plant is known to contain a diverse range of bioactive phytoconstituents distributed across its seeds, leaves, roots and stems. Phytochemical investigations reveal that R. communis contains several classes of secondary metabolites including alkaloids, flavonoids, terpenoids, phenolic compounds, sterols, coumarins, glycosides, and fatty acids [37]. The seeds contain approximately 45% fixed oil, composed primarily of ricinoleic acid (1) (Figure 6), which accounts for nearly 85–90% of the fatty acid composition of the oil. Other fatty acids present include palmitic acid (2), stearic acid (3), oleic acid (4), linoleic acid (5), linolenic acid (6), arachidic acid (7), and dihydroxystearic acid (8) (Figure 6) [38,39,40]. R. communis also contains several toxic proteins and nitrogen-containing compounds, particularly in the seeds. The most significant of these is ricin (9) (Figure 6), a highly potent type-2 ribosome-inactivating protein (RIP2). Ricin is composed of two polypeptide chains (A and B chains) and functions by inhibiting protein synthesis in cells, making it one of the most toxic plant-derived substances. Other related proteins include R. communis agglutinin (RCA), which is structurally similar to ricin but less toxic [41].

The plant also contains important alkaloids, particularly ricinine (10) and N-demethylricinine (11) (Figure 6), which have been isolated from the leaves and seeds [42]. Ricinine is considered the major alkaloid and occurs in measurable quantities in dried leaves (about 0.55%), along with smaller amounts of N-demethylricinine [43]. Phenolic compounds and flavonoids have been identified in the leaves of R. communis. Major phenolic compounds reported include gallic acid (12), gentisic acid (13), ellagic acid (14) and epicatechin (15), while flavonoids such as quercetin (16) and kaempferol (17) (Figure 6) derivatives have also been detected. Flavonoid glycosides such as kaempferol-3-xyloside (18) and quercetin-3-o-glucoside (19) (Figure 6) have also been isolated from the leaves [44,45]. Terpenoids and essential oil components are present in different parts of the plant including stems, leaves and seeds. Studies using gas chromatography–mass spectrometry (GC-MS) have identified compounds such as α-pinene (20), camphor (21), thujone (22), and camphene (23) (Figure 6) in the essential oils extracted from R. communis [46,47]. Other compounds such as lupeol (24) and 30-norlupan-3β-ol-20-one (25) have also been isolated from the outer layers of the seeds [48].

5. Traditional Uses of R. communis L.

R. communis has a long and diverse history in traditional medicine, with virtually all its parts being used for therapeutic purposes. The use of R. communis as a traditional remedy is widely documented across various geographical regions, particularly in South Africa, India, China, Nigeria, Ethiopia and Brazil (Figure 7) [49]. Traditional healers have employed the leaves as poultices or decoctions to treat skin sores, boils, and swellings, and have applied warmed, oil-coated leaves to the abdomen to relieve flatulence and stomach-ache [50]. In some African cultures, the leaves are also used to boost milk production in nursing mothers [51]. The roots are traditionally boiled or crushed into a paste for treating lumbago, sciatica, toothache, and other deep-seated pains [52]. Meanwhile, the bark is often crushed and applied to wounds to promote healing, showing its value in topically treating skin injuries. In addition to external applications, the seeds, once processed into castor oil, are used as a potent laxative to relieve constipation, and in some systems, they are administered in a controlled manner (after oil extraction) to stimulate digestion [53].

In addition, traditional medicine records include the use of castor oil for inducing labour, expelling placental matter, and as a purgative in children and the elderly [54].Importantly, traditional healers also use R. communis in skin-care applications, where castor oil is used topically to treat dermatological conditions such as dermatitis, eczema, and acne, due to its moisturizing and antimicrobial properties [55,56]. In some folk practices, infusions or juices of the leaves serve ritual or medicinal roles. For example, fresh leaf juice may be used as an emetic in cases of poisoning (e.g., overdose of opiates) or as part of cleansing rituals. Traditional African healers also massage castor oil into muscles and joints to reduce pain, using it as a remedy for rheumatic and arthritic discomfort [57].

6. Pharmacological Properties of Ricinus communis L.

R. communis is a medicinal species that has attracted significant scientific attention due to its wide range of pharmacological properties. These biological activities are largely attributed to its diverse phytochemical composition, which includes flavonoids, alkaloids, saponins, and phenolic compounds found in different parts of the plant such as the seeds, leaves, and roots using different extract types. Over the years, numerous in vitro and in vivo studies have validated its therapeutic potential, demonstrating activities relevant to the management of both acute and chronic diseases. The plant exhibits multiple pharmacological effects, including antioxidant, anti-inflammatory, antimicrobial, wound healing, anticancer, hepatoprotective, and antidiabetic activities, which collectively highlight its importance as a source of bioactive compounds for drug development and traditional medicine applications [58].

6.1. Antioxidant Activity

The antioxidant activity of R. communis is primarily attributed to its high content of phenolic compounds, flavonoids, and tannins, particularly in the leaves and seeds. These compounds act as free radical scavengers by donating hydrogen atoms or electrons to neutralize reactive oxygen species (ROS), thereby preventing oxidative damage to cellular macromolecules such as lipids, proteins, and DNA [59,60]. Studies using assays such as DPPH and ABTS have demonstrated that R. communis extracts exhibit strong radical scavenging capacity and reducing power, with methanol consistently emerging as the most effective extraction solvent.

Methanolic leaf extracts demonstrated some of the strongest antioxidant potential among the reported samples. Abbas et al., 2018 showed that methanol leaf extracts had a high total phenolic content (TPC) of 189.5 ± 4.2 mg GAE/g and total flavonoid content (TFC) of 68.3 ± 2.1 mg QE/g, indicating that the leaves are rich in bioactive phenolic and flavonoid compounds that contribute to antioxidant effects. This extract also showed a relatively low DPPH IC₅₀ value of 0.14 ± 0.02 mg/mL, which suggests strong free radical scavenging ability, since lower IC₅₀ values indicate higher antioxidant activity. Additionally, the extract inhibited 82.3% of linoleic acid oxidation, further confirming its effectiveness in reducing oxidative degradation and lipid peroxidation [61].

Similarly, the methanolic Soxhlet leaf extract reported by Gassim et al. 2024 showed even stronger antioxidant efficiency, with a slightly lower DPPH IC₅₀ value of 0.121 ± 0.02 mg/mL, suggesting improved radical scavenging activity compared with the conventional methanol extract. The extract also exhibited 85 ± 0.01% antioxidant activity, which was the highest among the tested solvents, indicating that Soxhlet extraction may enhance the recovery of antioxidant compounds from R. communis leaves [62].

Seed extracts also showed antioxidant properties, although lower than leaf-based methanol extracts. Vasco-Leal et al., 2021 reported that ethanolic seed extracts had a DPPH IC₅₀ value of 0.28 ± 0.05 mg/mL, which is higher than the leaf extracts. Since higher IC₅₀ values reflect weaker antioxidant activity, this suggests that seeds possess antioxidant compounds but may be less potent than leaf-derived methanolic extracts in scavenging free radicals [63].

6.2. Anti-Inflammatory Activity

The anti-inflammatory activity of R. communis has been widely reported in both in vitro and in vivo models, with leaf and root extracts showing significant inhibition of key inflammatory mediators such as prostaglandins, nitric oxide (NO), and pro-inflammatory cytokines (e.g., tumour necrosis factor (TNF-α) and interleukin (IL-6)). The mechanism involves suppression of cyclooxygenase (COX) and lipoxygenase (LOX) pathways, which are responsible for the synthesis of inflammatory mediators. Experimental animal studies confirm a significant reduction in inflammation, supporting its potential therapeutic use in disorders such as arthritis.

In the rat carrageenan-induced paw edema model, the hydroalcoholic leaf extract administered at 200 mg/kg produced a 58% reduction in paw edema after 4 hours, indicating strong acute anti-inflammatory activity. This effect was close to that of indomethacin, a standard non-steroidal anti-inflammatory drug (NSAID), which showed a 62% reduction, suggesting that R. communis leaf extract has comparable anti-inflammatory efficacy in suppressing edema formation caused by inflammatory mediators such as prostaglandins, histamine, and bradykinin. The root extract of R. communis also demonstrated anti-inflammatory potential in the rat cotton pellet granuloma model, which evaluates chronic proliferative inflammation. At a dose of 100 mg/kg, the extract caused a 45% reduction in granuloma weight compared with the untreated control, suggesting inhibition of fibroblast proliferation, tissue exudation, and chronic inflammatory tissue formation [64].

Further evidence from arthritic rat studies showed that R. communis extract modulated inflammatory cytokines and immune responses. Pro-inflammatory mediators such as interleukin-1 beta (IL-1β) decreased by 59%, interleukin-17a (IL-17a) by 52%, and receptor activator of nuclear factor kappa-B ligand (RANKL) by 47%, indicating suppression of inflammatory signaling and possible protection against joint destruction. At the same time, anti-inflammatory cytokines were elevated, with interleukin-4 (IL-4) increasing by 38% and interferon-gamma (IFN-γ) increasing by 42%, suggesting immunomodulatory effects that help restore inflammatory balance. Similarly, in chronic inflammation studies using complete Freund’s adjuvant (CFA)-induced arthritic rats, hydroalcoholic leaf extract at 200 mg/kg significantly reduced major pro-inflammatory biomarkers. Tumour necrosis factor-alpha (TNF-α) decreased by 63%, interleukin-6 (IL-6) by 57%, C-reactive protein (CRP) by 51%, and rheumatoid factor (RF) by 48% compared with the diseased control group. These reductions indicate that R. communis may suppress systemic inflammatory pathways involved in arthritis progression. The anti-inflammatory effects were also reported to be comparable to Withania somnifera, a known medicinal anti-inflammatory plant [65].

6.3. Antimicrobial Activity

R. communis demonstrates broad-spectrum antimicrobial activity against bacteria, fungi, and some viruses [66]. Extracts from leaves, seeds, and roots have shown inhibitory effects against pathogens such as Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The antimicrobial mechanism involves disruption of microbial cell membranes, inhibition of enzyme activity, and interference with microbial metabolism, with bioactive compounds such as alkaloids, saponins, and flavonoids contributing to this activity [67].

The strongest antibacterial activity was observed against Staphylococcus aureus, where the methanolic leaf extract produced a zone of inhibition of 22 ± 0.2 mm and a minimum inhibitory concentration (MIC) of 12.5 mg/mL. A larger zone of inhibition and lower MIC indicate stronger antimicrobial potency, suggesting that R. communis leaf extract is particularly effective against this Gram-positive bacterium. This may be attributed to bioactive compounds such as flavonoids, alkaloids, phenolics, tannins, and terpenoids present in the leaves, which can disrupt bacterial membranes, inhibit enzyme systems, and interfere with microbial metabolism [68].

Moderate antibacterial activity was reported against Escherichia coli, with a zone of inhibition of 19 ± 0.3 mm and an MIC of 25.0 mg/mLSimilarly, Klebsiella pneumoniae showed slightly lower susceptibility, with a zone of inhibition of 18 ± 0.3 mm and the same MIC of 25.0 mg/mL These findings suggest that R. communis leaf methanolic extract can inhibit common Gram-negative enteric pathogens, although at relatively higher concentrations compared to S. aureus. The comparatively lower susceptibility of Gram-negative bacteria may be explained by the presence of an outer lipopolysaccharide membrane, which acts as an additional permeability barrier against phytochemicals and antimicrobial agents [69].

The weakest antibacterial activity was observed against Pseudomonas aeruginosa, which had a very small zone of inhibition of 9 ± 0.3 mm and the highest MIC value of 50.0 mg/mL This indicates strong resistance of P. aeruginosa to the methanolic extract. This reduced sensitivity is expected because P. aeruginosa possesses highly efficient multidrug efflux pumps, biofilm-forming capacity, and low outer membrane permeability, all of which contribute to its intrinsic resistance to many plant-derived antimicrobials [70].

6.4. Wound Healing Activity

R. communis exhibits significant wound healing properties, particularly through the topical application of castor oil and leaf extracts. The mechanism involves multiple phases of wound repair, including enhanced collagen synthesis, increased fibroblast proliferation, and accelerated epithelialization. Ricinoleic acid, a major component of castor oil, plays a key role in promoting tissue regeneration and maintaining a moist wound environment, which facilitates the healing process [71]. Experimental studies have demonstrated faster wound contraction rates and improved tensile strength of healed tissue in treated groups compared to controls.

In the full-thickness rabbit wound model (n = 16), topical application of R. communis leaf extract was compared with untreated wounds. By day 14, wound contraction reached approximately 85% in treated wounds compared to 70% in the untreated control group, indicating improved wound closure in the treated animals, although the study reported that this difference was not statistically significant. This suggests that while the extract may have enhanced healing, its effect on wound contraction alone was not sufficiently strong to show a clear statistical advantage over natural healing. However, histological observations revealed important tissue-level improvements. By day 3, treated wounds showed reduced inflammation, indicating an anti-inflammatory effect of the leaf extract. Reduced inflammatory cell infiltration in early wound healing is important because prolonged inflammation can delay tissue repair. By day 7, treated tissues demonstrated greater tissue strength, increased formation of new blood vessels (angiogenesis), and better organized collagen fibres compared to controls. These findings suggest that R. communis may accelerate the proliferative phase of healing by improving fibroblast activity and extracellular matrix formation. By day 14, the treated wounds exhibited pronounced vascularization, which reflects improved oxygen and nutrient delivery to regenerating tissue and may contribute to better structural recovery [72].

In the rat excision wound model, treatment with castor oil, which is rich in ricinoleic acid, demonstrated stronger wound healing activity than the leaf extract model. By day 10, wound contraction was 92% in treated rats compared with 78% in the control group, showing a marked acceleration of wound closure after castor oil treatment. This indicates that castor oil may have a more pronounced effect on tissue repair and wound contraction than untreated healing. Histologically, the treated wounds showed increased collagen deposition, which is critical for restoring skin integrity and wound tensile strength. Additionally, tensile strength increased by 35%, suggesting that healed tissues were mechanically stronger and more resistant to re-injury [73].

6.5. Anticancer Activity

The anticancer potential of R. communis is largely associated with ricin, a highly potent ribosome-inactivating protein found in the seeds. Ricin inhibits protein synthesis by inactivating the 60S ribosomal subunit, leading to apoptosis (programmed cell death) in cancer cells [74]. Other phytochemicals, such as flavonoids and phenolic compounds, contribute to anticancer effects through antioxidant mechanisms and modulation of cell signalling pathways [75]. Experimental studies have shown that extracts of R. communis can inhibit the proliferation of various cancer cell lines, with seeds demonstrating promising activity against breast cancer cell lines such as oestrogen-positive Michigan cancer foundation (MCF-7).

In the A375 melanoma cell line, treatment with an aqueous plant extract showed an IC₅₀ value of 48 µg/mL after 48 hours, indicating moderate cytotoxic activity against melanoma cells. Since IC₅₀ represents the concentration required to inhibit 50% of cell viability, a lower value reflects stronger cytotoxic potency. The study reported dose-dependent cytotoxicity, meaning that increasing extract concentration progressively reduced cancer cell survival [76].

In MCF-7 oestrogen receptor-positive (ER⁺) breast cancer cells, the methanolic seed extract demonstrated clear time- and dose-dependent anticancer effects. At 24 hours, the IC₅₀ was 85 ± 4 µg/mL, which decreased to 62 ± 3 µg/mL after 48 hours, indicating increased cytotoxicity with prolonged exposure. This reduction in IC₅₀ over time suggests cumulative antiproliferative effects of the extract. The study also reported increased apoptosis, showing that the extract promoted programmed cell death in breast cancer cells [77].

In the A549 lung cancer cell line, crude ricin, a toxic seed protein derived from R. communis, demonstrated marked cytotoxicity with an IC₅₀ of 53.65 ± 0.78 µg/mL after 48 hours. The study showed that ricin induced apoptosis, reduced cancer cell migration, and increased autophagy. Reduced migration suggests an anti-metastatic effect, meaning ricin may inhibit the spread of tumour cells. Increased autophagy may reflect cellular stress or self-digestion mechanisms that contribute to cancer cell death. Together, these findings indicate that ricin has multiple anticancer actions, including suppression of tumour growth, survival, and invasiveness [78].

The most potent anticancer activity was observed with ricin immunotoxins, which showed extremely low IC₅₀ values of 0.5–2 ng/mL across various cancer cell types after 24 hours. These values are substantially lower than those reported for crude extracts, indicating very high cytotoxic potency. Ricin immunotoxins are engineered therapeutic molecules in which ricin-derived toxic proteins are conjugated to antibodies or ligands that selectively target tumour cells. The study noted that targeted delivery reduced systemic toxicity, which is important because ricin alone is highly poisonous. This suggests that biotechnological modification of ricin may improve its therapeutic safety while retaining strong anticancer efficacy [79].

6.6. Hepatoprotective Activity

The hepatoprotective effects of R. communis have been demonstrated in experimental models of chemically induced liver damage (e.g., carbon tetrachloride-induced hepatotoxicity) [80]. Its hepatoprotective potential has been demonstrated using a D-galactosamine-induced hepatitis model in rats, with effects compared to the standard drug silymarin. Methanolic extract of R. communis leaves showed notable antioxidant activity through free radical scavenging assays, while phytochemical analysis identified rutin as a major bioactive compound. Liver injury resulted in elevated serum liver enzymes (ALT, AST, ALP and MDA). Treatment with the leaf extract significantly restored these biochemical parameters toward normal levels.

R. communis leaf methanolic extract (MERCL) has significant hepatoprotective effects in D-galactosamine-induced rat hepatitis, with benefits increasing in a dose-dependent manner. At 200 mg/kg and 400 mg/kg, the extract reduced key liver damage markers such as ALT, AST and ALP, indicating protection against liver cell injury. It also lowered malondialdehyde (MDA), showing reduced oxidative stress, while increasing superoxide dismutase (SOD) and reduced glutathione (GSH), which reflect improved antioxidant defence. X The 400 mg/kg dose showed stronger effects and performed similarly to silymarin, the standard hepatoprotective drug, suggesting that R. communis may help protect liver tissue through antioxidant, anti-inflammatory, and membrane-stabilising mechanisms [81].

6.7. Antidiabetic Activity

R. communis has demonstrated significant antidiabetic potential in both streptozotocin- and alloxan-induced diabetic rat models. Ethanolic and aqueous-ethanolic leaf extracts reduced elevated blood glucose levels, improved body weight, and restored several biochemical abnormalities associated with diabetes. In streptozotocin (STZ) induced diabetic rats, the ethanolic leaf extract at 600 mg/kg showed the strongest hypoglycaemic effect, reducing blood glucose by approximately 32%, with activity comparable to glibenclamide. The extracts also improved liver function markers (AST, ALT and bilirubin), kidney function indicators (creatinine and urea), and electrolyte balance, indicating protective effects against diabetic complications [82].

Similarly, studies on alloxan-induced diabetic rats reported that ethanolic root extracts significantly lowered fasting blood glucose from 379 ± 72 mg/dL to 149 ± 11 mg/dL after 20 days of treatment. Another study showed a 61.97% reduction in blood glucose levels within seven days of treatment. These antidiabetic effects are thought to be associated with phytochemicals such as flavonoids, alkaloids, saponins, rutin, and α-thujone, which may stimulate insulin secretion, promote pancreatic β-cell repair, and inhibit glucose absorption [83].

6.8. Analgesic (Pain Receptor Modulation)

R. communis provides general pain relief primarily through antinociceptive mechanisms that target peripheral nociceptors and central nervous system pathways. The strongest evidence comes from ricinoleic acid, the major fatty acid in castor seed oil, tested in the formalin-induced pain model at 100 mg/kg. This model has two phases of pain: an early neurogenic phase and a late inflammatory phase. Ricinoleic acid showed 35% inhibition in the early phase and 62% inhibition in the late phase, indicating stronger activity against inflammatory pain than immediate nerve-mediated pain. The proposed mechanism involved transient receptor potential vanilloid 1 (TRPV1) activation followed by receptor desensitisation and depletion of substance P, a neurotransmitter involved in pain signalling [84].

The hydroethanolic seed extract showed significant analgesic effects in the tail-flick test, which measures central thermal pain response and spinal reflexes. At a dose of 200 mg/kg, the extract caused a 58% increase in pain-response latency, meaning animals tolerated thermal pain for longer before responding. This indicates central analgesic activity. Mechanistically, the extract appeared to act through spinal μ-opioid receptor activation and N-methyl-D-aspartate (NMDA) receptor modulation, with effects being partially reversible by naloxone, an opioid antagonist [85].

Similarly, the aqueous root bark extract demonstrated analgesic activity in the hot plate test, another central pain model sensitive to supraspinal responses. At 150 mg/kg, the extract produced a 51% increase in latency, indicating delayed pain perception and improved tolerance to thermal stimuli. Unlike the seed extract, this activity was reported as non-opioid mediated, involving nitric oxide (NO) inhibition and blockade of voltage-gated calcium (Ca²⁺) channels [86].

The root-derived sesquiterpenes (ricinusoids) showed notable effects in the acetic acid-induced writhing model, which reflects peripheral visceral pain and inflammatory nociception. At 50 mg/kg, the ricinusoids caused a 64% reduction in writhing episodes, making this one of the strongest analgesic responses. The mechanism was linked to gamma-aminobutyric acid A (GABA(_A))-mediated central nervous system depression, which suggests enhanced inhibitory neurotransmission and reduced pain signalling [87].

7. Industrial Applications of R. communis L.

Industrially, the hydroxyl functionality of ricinoleic acid makes refined castor oil an exceptional renewable feedstock for producing specialty chemicals such as sebacic acid (26) and 12-hydroxystearic acid (27) (Figure 8) that are used in lubricants, plasticisers, surfactants and high-value polymer intermediates [88].

Castor-derived monomers and oligomers are exploited in polymer science, including the formulation of polyamides and polyurethanes, as well as in biodegradable materials, where the hydroxyl group enhances reactivity and improves final material properties [89]. Castor is also investigated as a non-edible oilseed for biodiesel and other bio-based fuels, because of its high oil yield and favourable physicochemical properties when blended or chemically modified [90]. In pharmaceutical and cosmetic formulations, refined castor oil is commonly used as an excipient, emollient, and solubiliser due to its rheological properties and improved oxidative stability after refining [91].

R. communis also serves as a key precursor in the production of specialized polyamides, such as Nylon-11, which are utilized in the automotive and textile industries due to their exceptional thermal stability and chemical resistance. Furthermore, castor oil derivatives are essential in the formulation of high-grade lubricants and hydraulic fluids, as they maintain consistent viscosity and stability across a wide temperature range. Its moisture-resistant properties also make it a widely used ingredient in the cosmetics, paints, and coatings industries, where it serves as a sustainable alternative to petroleum-derived chemicals [92].

The biodiesel production from R. communis is also considered a promising renewable energy pathway because the plant is a non-edible oilseed crop with high oil content, making it suitable for biodiesel without directly competing with food resources. The high viscosity and low pour point of castor oil biodiesel make it a versatile alternative fuel; however, its relatively density often requires blending with conventional diesel to optimize engine performance. Researchers have emphasized that the transesterification process efficiently converts the oil's triglycerides into fatty acid methyl esters, thereby, producing a renewable energy source that helps mitigate the environmental impact of fossil fuels. The biodiesel production process generally begins with cultivation of R. communis, followed by harvesting and seed extraction. The seeds are then processed to obtain castor oil, which undergoes transesterification, where triglycerides react with alcohol (commonly methanol) in the presence of a catalyst to produce biodiesel (fatty acid methyl esters) and glycerol as a by-product [93,94,95]. Table 1 summarises some of the major industrial sectors in which R. communis is utilised, together with their specific applications and industrial significance.

8. Additional Applications of R. communis L.

8.1. Weed Control (Herbicidal/Allelopathic) Applications

R. communis demonstrates potent herbicidal and allelopathic properties for weed control, primarily through its leaf extracts rich in phenolics and terpenoids [103]. In vitro studies have revealed that aqueous leaf extracts of R. communis inhibit the seed germination of weeds such as Bidens bipinnata by up to 100% at 25 g L⁻¹ concentrations. These extracts also reduce seedling hypocotyl and radicle lengths via disruption of cell division and membrane permeability [104,105]. Foliar applications in pot experiments induced chlorosis, necrosis, reduced plant height and chlorophyll levels in B. bipinnata, with symptoms graded as strong phytotoxicity (grade 5) at 37.5 g L⁻¹. These effects were linked to interference in photosynthesis and membrane permeability [106].

8.2. Tick Control (Acaricidal) Activity

R. communis demonstrates notable tick control (acaricidal) activity through both repellent and toxic effects against different tick species. Its essential oil has been shown to moderately repel ticks such as Ixodes ricinus, reducing their host-seeking behaviour, which indicates interference with sensory or behavioural mechanisms [107]. More pronounced effects have been observed with crude extracts, particularly leaf extracts, where strong dose- and time-dependent mortality against ticks has been reported. Methanolic extracts are especially effective, achieving complete (100%) tick mortality at higher concentrations within relatively short exposure periods. Aqueous and ethanolic extracts also produce high mortality rates, although their efficacy is slightly lower compared to methanolic extracts [108].

8.3. Phytoremediation of soil

R. communis has emerged as a promising phytoremediation species for contaminated soils because of its rapid growth, extensive root system, tolerance to abiotic stress, and ability to accumulate or stabilize pollutants without major reductions in biomass productivity. Across the reviewed studies, its application spans remediation of organic pollutants, heavy metals, mine tailings, saline soils, and chemically assisted remediation systems, showing that the plant can function through both phytoextraction and phyto stabilization mechanisms [109,110].

One of the major reasons R. communis is valuable in phytoremediation is its high adaptability to harsh soil conditions [111]. The species is fast-growing, produces substantial biomass, and develops a deep, widespread root architecture capable of penetrating contaminated substrates and accessing pollutants beyond the superficial soil layer. This extensive root system increases contact with contaminated soil, improving pollutant uptake and stabilization efficiency. Additionally, the plant tolerates drought, salinity, and metal stress, which makes it particularly useful in degraded and marginal environments where conventional crops may fail [112].

Besides heavy metals, R. communis also demonstrates effectiveness in remediation of persistent organic pollutants (POPs). Rissato et al., 2015 investigated castor bean in greenhouse experiments involving soils contaminated with organochlorine pesticides. The study showed that castor could survive and grow in polluted soils while promoting pollutant reduction. Its phytoremediation effect was linked not only to direct uptake but also to interactions within the rhizosphere, where root-associated microbial activity may facilitate degradation of contaminants. Thus, R. communis contributes to remediation through both plant-based absorption and indirect stimulation of biodegradation processes [113]. Chelating agents such as citric acid (CA), ethylenediamine disuccinic acid (EDDS), EDTA, and nitrilotriacetic acid (NTA) can improve heavy metal bioavailability in soils, enhancing uptake by R. communis. Research suggests that these chelators increase rhizospheric metal mobility and improve accumulation of metals like Pb and Cd in castor tissues, thereby increasing remediation efficiency. This indicates that R. communis can be integrated into engineered phytoremediation systems [114].

9. Clinical Studies of R. communis L.

Clinical studies on R. communis remain limited, with most evidence derived from preclinical investigations, while only a few studies have examined its effects directly in humans. The available clinical literature primarily focuses on castor-derived formulations such as castor oil and R. communis extracts, particularly for antimicrobial, anti-inflammatory, and musculoskeletal uses. Despite its broad ethnomedicinal applications, high-quality randomized human trials remain scarce, making clinical translation challenging. One of the most notable human clinical investigations involved the use of R. communis as a denture-cleaning and antimicrobial agent. A randomized clinical study showed that castor-based denture cleanser solutions exhibited antimicrobial activity against oral pathogens and were beneficial in controlling denture-associated candidiasis and microbial biofilm. Although sodium hypochlorite demonstrated stronger biofilm-removal properties, R. communis preparations showed good patient acceptance and therapeutic promise as a safer and cost-effective alternative for oral hygiene manage [115].

Clinical applications of R. communis have also been explored in traditional medicine, particularly in Ayurvedic practice for inflammatory and musculoskeletal disorders. Comparative clinical studies evaluated castor oil (Eranda taila) and related formulations in the treatment of conditions such as Amavata, which resembles rheumatoid arthritis, and Gridhrasi, which is clinically associated with sciatica syndrome. These studies reported improvements in pain, stiffness, and inflammatory symptoms, supporting the traditional analgesic and anti-inflammatory role of castor-based preparations [116]. Overall, while R. communis L. demonstrates promising therapeutic potential in oral healthcare, inflammatory disorders, and traditional medicinal systems, the clinical evidence remains narrow and methodologically weak. Most studies cited in the reviewed articles emphasize that its anticancer, antioxidant, hepatoprotective, antidiabetic, and broader anti-inflammatory effects are still predominantly supported by in vitro and animal experiments rather than robust human trials. Consequently, larger, well-designed randomized controlled clinical studies are required to confirm efficacy, establish safe dosing, and validate standardized therapeutic formulations before broader clinical adoption can be recommended [117].

10. Toxicity of R. communis L.

R. communis presents several notable disadvantages that limit its safe cultivation and use despite its economic value. One of the primary drawbacks is its high toxicity; the seeds contain ricin and related lectins such as Ricinus communis agglutinin 120 (RCA₁₂₀), which are among the most potent plant toxins known and can cause severe poisoning in humans and animals if ingested or inhaled [118]. The detection of α-thujone in R. communis suggests that, despite the plant’s therapeutic potential, caution is necessary when using extracts for medicinal purposes. Mboyazi et al., 2020 emphasized the importance of toxicity screening of plant-derived compounds because natural products are often incorrectly assumed to be completely safe. Their in-silico toxicity analysis demonstrated that some phytocompounds from R. communis may possess toxicological risks, thereby supporting the need for biosafety evaluation before clinical or pharmaceutical use [119].

Inhalation, ingestion, or injection of this substance is toxic, a lethal dose can be as low as five to ten micrograms per kilogram [120]. Oral exposure commonly produces immediate gastrointestinal symptoms, including severe abdominal pain, nausea, vomiting, and diarrhoea. Gastrointestinal haemorrhage has been reported and can contribute to marked fluid loss and hypovolemic shock [121]. Following ingestion, systemic absorption can result in toxin accumulation in the liver and spleen, leading to subsequent hepatic injury, renal impairment, and hypotension that may progress to peripheral vascular collapse in severe cases. Reported human cases emphasize that the clinical course after ingestion varies with dose, seed chewing, and any co-ingested castor oil. But supportive measures aimed at correcting hypovolemia and managing organ dysfunction remains the cornerstone of treatment [122].

The cytotoxic potential of R. communis extracts has also been evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell proliferation assay across different cell lines (Table 2). The results indicated that chloroform and ethyl acetate extracts exhibited moderate cytotoxic activity against the A549 cell line and suggest that R. communis possesses notable cytotoxic properties, although the activity varies depending on the type of extract and cell line used.

11. Future Directions and Research Gaps for R. communis L.

Although a wide range of pharmacological activities have been reported for R. communis, several critical research gaps remain that need to be conclusively addressed to fully exploit its therapeutic and industrial uses. One major gap lies in the isolation and characterization of specific bioactive compounds responsible for its pharmacological effects. While some studies have identified phytochemicals such as alkaloids, flavonoids, and highly potent protein ricin, the isolation characterization, and evaluation of these bioactive compounds and their possible pharmacological activities especially cytotoxic and antidiabetic activities remain limited. There is also a need for isolation and characterization of specific bioactive compounds responsible for the observed pharmacological activities, using advanced high throughput screening technologies. Another important limitation is the lack of extensive mechanistic studies. The toxicity and safety profile of R. communis has been a matter of concern, mostly due to ricin, a highly toxic compound. In this respect, most of the existing studies are based on in vitro models, with minimal in vivo or clinical studies.it

Future studies should focus more on toxicological evaluations, including acute, sub-chronic, and chronic toxicity assessments, as well as safe dosage determination ranges and comprehensive risk assessments. There is also an evident lack of clinical trials. This lack of clinical trials is another crucial point despite the pharmacological properties suggested in the preclinical studies (pharmacology), there is limited translation into human studies. Only through rigorous clinical trials that assess efficacy, safety, pharmacokinetics, and pharmacodynamics in human subjects can reliable recommendations be made concerning the therapeutic applications of these findings. Standardization of extracts is also inadequately addressed. Different extraction methods, plant parts and geographical sources often produce inconsistent results. Future research should aim at developing protocols to standardize extractions and robust quality control measures to ensure reproducibility and reliability of findings. Another emerging area is the application of nanotechnology and drug delivery systems. Initial studies involving R. communis derived nanoparticles suggest enhanced biocompatibility and lower toxicity. Nonetheless, this area remains underexplored. More studies are necessary to strategize nanoparticle synthesis, assess targeted drug delivery systems, and assess long-term safety measures.

12. Materials and Methods

This review article was carried out by searching electronic databases, including Google Scholar, Elsevier, MDPI, Scopus, PubChem and Science Direct, identify and retrieve relevant articles and research papers of R. communis L. published from 2015 to 2025. All chemical structures were drawn using ChemDraw Ultra® 8.0 Software.

13. Conclusions

This review highlights R. communis L. as a plant of exceptional phytochemical diversity and multifunctional relevance, bridging traditional medicine, pharmacological research, and industrial biotechnology. The dominance of ricinoleic acid in castor oil, together with the presence of alkaloids, phenolics, flavonoids, and bioactive proteins, provides a clear biochemical basis for many ethnomedicinal practices and experimentally validated pharmacological effects, particularly anti-inflammatory, antimicrobial, antioxidant, wound-healing, and laxative activities. Although taxonomically monotypic, R. communis exhibits marked intraspecific variation, with cultivar- and tissue-dependent differences in chemical composition, oil yield, and bioactivity. These variations present opportunities for targeted selection of cultivars for medicinal, ornamental, or industrial purposes. Industrially, castor oil remains a strategically important renewable resource, enabling the production of high-value chemicals, polymers, pharmaceuticals, cosmetics, and biofuels. Nonetheless, the inherent toxicity of ricin present in raw seeds continues to pose significant safety and regulatory challenges, thereby reinforcing the need for refined products and controlled processing.