The most recent outbreak of 2019 novel coronavirus, named as COVID-19, caused pneumonia epidemic in Wuhan with 2,121 deaths cases as of February 20^th 2020. Identification of effective antiviral agents to combat the novel coronavirus is urgently needed. Citrus fruit peel or wild citrus are rich in flavonoid, and is clinically documented for roles in relief of cough and promotion of digestive health. Therefore, citrus fruits are assumed to possess antivirus activities or enhance the host immunity. A previous study found that hesperetin could act as a high potent inhibitor of SARS-CoV 3CLpro. We determined six flavonoid compounds content of in three citrus species by using LC-MS technique. The content of naringin and naringenin was at higher levels in pummelo. Hesperetin and hesperidin were highly accumulated in mandarin and sweet orange. The subsequent in vitro and in vivo experiments indicated that naringin could inhibit the expression of the proinflammatory cytokines (COX-2, iNOS, IL-1β and IL-6) induced by LPS in Raw macrophage cell line, and may restrain cytokine through inhibiting HMGB1 expression in a mouse model. The results revealed that naringin may have a potential application for preventing cytokine storm. We simulated molecular docking to predict the binding affinity of those flavonoids to bind Angiotensin-converting enzyme 2 (ACE 2), which is a receptor of the coronavirus. Consideration of the potential anti-coronavirus and anti-inflammatory activity of flavonoids, the citrus fruit or its derived phytochemicals are promising in the use of prevention and treatment of 2019-nCoV infection.

Following the analysis of terpenes present in new lemon and grapefruit “IntegroPectin” pectins obtained via the hydrodynamic cavitation of industrial lemon and grapefruit processing waste, the HPLC-MS analysis of the flavonoid compounds reveals the presence of eriocitrin, naringin, hesperidin and kaempferol typical of the respective citrus fruits. The pectic fibers rich in rhamnogalacturonan-I “hairy” regions act as chemical sponges adsorbing and concentrating at their outer surface highly bioactive citrus flavonoids and terpenes. These findings, together with the unique molecular structure of these new whole citrus pectins, provide preliminary insight into the broad-scope and powerful biological activity of these biomaterials. Numerous new biomedical applications beyond prevention and treatment of microbial infections and neurodegenerative disease are anticipated.

Citrus flavonoids are well-known for beneficial effects at the cardiovascular and cardio-metabolic level, but often the encouraging in vitro results are not confirmed by in vivo approaches; also clinical trials are inconsistent. The limited bioavailability of them can be, at least in part, the reason of these discrepancies. Therefore many efforts were performed towards the improvement of their bioavailability. Hydrodynamic cavitation methods were successfully applied to the extraction of byproducts of the Citrus fruits industry, showing high process yields and affording stable phytocomplexes, known as IntegroPectin, endowed with great amounts of bioactive compounds and high water solubility. Cardioprotective effects of grapefruit IntegroPectin were evaluated by an ex vivo ischemia/reperfusion protocol. A further pharmacological characterization was carried out to assess the involvement of mitochondrial potassium channels. Grapefruit IntegroPectin, where naringin represented 98% of flavonoids, showed anti-ischemic cardioprotective activity, better than pure naringenin (the bioactive aglycone of naringin). On cardiac isolated mitochondria, this extract confirmed that naringenin/naringin were involved in the activation of mitochondrial potassium channels. The hydrodynamic cavitation-based extraction confirmed a valuable opportunity for the exploitation of Citrus fruits waste, with the end product presenting high levels of Citrus flavonoids and an improved bioaccessibility that enhances its nutraceutical and economic value.

Colistin is used in treatment against gram-negative bacteria. It causes toxic effects due to oxidative stress in a dose-dependent manner. Naringin is a flavonoid with strong antioxidant properties found naturally in many plants, especially citrus fruits. This study aimed to determine the protective effects of NRG in CLS-induced sciatic nerve injury. Thirty-five male Spraque rats were randomly divided into five groups: control, NRG, CLS, CLS+NRG50, and CLS+NRG100. CLS was administered orally at a 15mg/kg for seven days. NRG was administered orally at 50 or 100 mg/kg for seven days. CLS caused toxic damage in sciatic nerve tissue by increasing MDA and decreasing antioxidant capacity (SOD, CAT, GPx, and GSH); increasing NF-κB, TNF-α, nNOS release; increasing apoptotic factor (Caspase-3); decreasing HO-1 and nCAM; and inducing 8-OHdG, MAPK and GFAP. NRG, on the other hand, reversed all these changes in sciatic nerve tissue and reduced CLS-induced oxidative stress damage, inflammatory damage and apoptotic damage. These effects were more effective at the 100mg/kg dose of NRG than at the 50mg/kg dose. In sciatic nerve tissue, CLS-induced sciatic nerve toxicity with increased oxidative stress, inflammation, and apoptotic damage. NRG showed a protective effect against CLS-induced sciatic nerve toxicity.