Due to the low content, few studies are focused on the volatile compounds of Phlomoides rotata (Benth. ex Hook. f.) Mathiesen (PR, syn. Lamiophlomis rotata (Benth.) Kudô). However, such volatile compounds may have important pharmacological activities such as antioxidant, anticancer. In order to identify the chemical markers (CMs) in the essential oils (Es) and explore the potential bioactivities, we first conduct a thoroughly investigation on the volatile compounds and evaluate their anti-oxidant activities (AOAs), to the best of our knowledge. Light yellow Es with a fresh and elegant smell are obtained by hydro-distillation with an average yield of 0.11% (mL/g). After separation through cryoprecipitation, the crystals (Cs) and EOs removed crystals (RCs) were gotten, respectively. A total of 81 components are qualified and quantified in the Es, Cs and RCs, in which 44 ones are first reported from PR. As for content, the main compounds are long-chain fatty acids (LCFAs) and their esters. Among them, palmitic acid (PA), myristic acid (MA), linoleic acid (LA), oleic acid (OA) and methyl palmitate are highlighted, Besides, hexahydrofarnesyl acetone and phytol are also prominent Four kinds of C13-norisoprenoids are first reported from PR, in which, trans-β-damascenone is potent in flavour. In sum, these eight representative compounds can be chosen as the CMs. The AOAs of Es, Cs, RCs and four CMs such as PA, MA, LA and OA are evaluated by in vitro assays. In general, PA and MA present pro-oxidant activities (POAs) or weak AOAs. LA and OA show POAs or weak AOAs in lower concentration group, whereas demonstrate medium or strong AOAs in higher concentration group. Usually, the RCs demonstrate stronger AOAs and the Cs present weaker AOAs compared with those of the corresponding Es, which should be related to their different content of PA. This study can give some hints on the utilization of such Es which are abundant in LCFAs.

Due to the low content, few studies are focused on the essential oils (EOs) of Phlomoides rotata (Benth. ex Hook. f.) Mathiesen (syn. Lamiophlomis rotata (Benth.) Kudô. This plant has been used to treat rheumatic arthritis and grasserie in China. However, such EOs may have important pharmacological activities such as anti-cancer. To identify the chemical markers (CM) in the EOs and evaluate their antioxidant activities (AAs), we firstly conduct a thoroughly investigation on their chemicals and AAs, to the best of our knowledge. Light yellow EOs with fresh and elegant smell are obtained by hydro-distillation with average yield 0.11% (volume mL/weight g). The crystals are separated from the EOs through cryoprecipitation, respectively. A total of 81 components are qualified and quantified in the EOs, crystals and EOs removed crystals, in which 44 ones are first reported. As for content, the main compounds are long-chain fatty acids (FAs) and their esters. The most abundant one n-hexadecanoic acid (palmitic acid, PA) accounting for 43.15-54.8%, 58.49-64.57% and 15.9-41.1%, in the EOs, crystals and EOs removed crystals, respectively. Seven compounds including PA, tetradecanoic acid, linoleic acid, oleic acid, methyl hexadecanoate, hexahydrofarnesyl acetone and phytol can be chosen a the CMs in these EOs. The AAs are evaluated through in vitro assays. PA presents pro-oxidant activities in a concentration dependence manner. Usually, the EOs removed crystals demonstrate stronger AAs, and the crystals demonstrate weaker AAs compared with that of the corresponding EOs, which is related to the different content of PA in these samples. This study can give some hints for the utilization of such EOs which are abundant in FAs such as PA.

Limited research has been conducted on the metabolites present in the essential oils (EOs) of Phlomoides rotata (Benth. ex Hook. f.) Mathiesen (PR, syn. Lamiophlomis rotata (Benth.) Kudô), and their potential pharmacological activities, such as antioxidant properties, are often overlooked. We conducted a metabolomics-based screening to identify the characteristic metabolites (CMs) in the EOs extracted from PR. Meanwhile, we evaluated their in vitro antioxidant activities (AOAs). The EOs obtained through hydro-distillation are characterized by a light yellow color and a fresh, elegant fragrance. Cryoprecipitation was used to separate the crystals (Crs) from the EOs, resulting in the crystal-free EOs (CFs). A total of 121 components are identified and quantified in the EOs, Crs, and CFs. Among them, 84 were reported for the first time from such EOs. The major compounds include long-chain fatty acids (LCFAs) and their esters, such as palmitic acid (PA), myristic acid (MA), linoleic acid (LA), oleic acid (OA), stearic acid, and methyl palmitate (MP). Furthermore, 11 kinds of apocarotenoids (also called norisoprenoids) were first systematically investigated. Among them, eight C13-norisoprenoids, with trans-β-damascenone (DN) being particularly notable for its flavor, were identified. A sum of 11 CMs are screened , including PA, MA, LA, OA, MP, hexahydrofarnesyl acetone, phytol (PT), DN, stearic acid, linalool, and hexanal. These CMs are biosynthesized through FAs and 2-C-Methyl-D-erythritol 4-phosphate/1-Deoxy-D-xylulose 5-phosphate pathways. The in vitro AOAs of EOs, Crs, CFs, and seven selected CMs (PA, MA, LA, OA, MP, PT, and DN) were evaluated. Generally, PA and MA exhibited pro-oxidant activities (POAs) or weak AOAs. LA and OA demonstrated POAs or weak AOAs at lower concentrations, but at higher concentrations, they displayed medium to strong AOAs. Importantly, the CFs typically exhibited stronger AOAs compared to the corresponding EOs and Crs, potentially due to variations in their PA content. Overall, this study provides valuable insights into the potential utilization of EOs from PR.