Phytochemical analysis and biological activities of Odontites vuglaris Moench.

Odontites vulgaris Moench (Orobanchaceae) is an annual herbaceous plant, used for medicinal purposes since the ancient times [1]. It is used in Mongolian medicine to cool the blood, alleviate itching, promote detoxification and diuresis, and relieve symptoms of rheumatoid arthritis [1]. Iridoids, phenylethanoid glycosides, flavonoids, triterpenes, and organic acids represent the main identified phytochemicals, though its true bioactive compounds remain unidentified [2]. In this study, we examined an Italian species of O. vulgaris from the Maiella National Park in central Italy, in order to characterize its phytochemical and biological profile. To this end, an ethanolic dry extract from the aerial parts (20:1 drug/extract ratio) was prepared through 96 h maceration, followed by evaporation under vacuum. In order to identify the characteristic compounds, the extract was subjected to chromatographic separation, using an elution system composed of n-butanol and distilled water (82:18 v/v) and then a mixture of n-butanol, methanol, and distilled water (70:10:30 v/v/v). The isolated compounds were identified through NMR and MS analysis and identified as quinic acid and the iridoids aucubin, catalpol, shanzhiside methyl ester, melampyroside, 8-epi-loganin, and caryoptoside [3]. A screening of diverse bioactivities, including the scavenging activity against DPPH and ABTS radicals, ability to affect AGE (advanced glycation end-products) generation, cytotoxicity in H69 human cholangiocytes and RAW 264.7 murine macrophages, and cytoprotection towards oxidative damage induced by tert-butyl hydroperoxide (tBOOH), was performed according to standardized methods [3]. The extract exhibited radical scavenging properties against both DPPH· and ABTS·+ radicals, without affecting the AGE formation, with an efficacy less potent than the positive control trolox. In the tested cell lines, the extract showed toxicity signs starting from the highest concentration of 600 µg/mL, where cell viability was reduced by about 40% of the control. The same concentration also increased the intracellular oxidative stress, increasing levels of reactive oxygen species more than three times in H69 cells and more than twice in RAW 264.7 cells ROS with respect to control. In both cell lines, nontoxic concentrations of the extract were able to protect the cells from the oxidative damage induced by tert-butyl hydroperoxide (tBOOH), by restoring the cell viability and lowering the oxidative stress. However, at non-toxic concentrations, the extract exhibited cytoprotective effects towards the tBOOH-induced oxidative damage in both cell lines, by restoring viability and reducing oxidative stress. Present findings highlight Italian O. vulgaris as a promising source of bioactive compounds, with some identified for the first time. Notably, the cytoprotective properties of the extract agree with previous evidence [2] and suggest a possible contribution of the identified compounds. However, further investigations to better characterize the bioactivities of the tested extract and its metabolites are needed. [1] Ji et al. (2021). Front. Pharmacol., 12, 707687. [2] Wang et al. (2023) J. Asian Nat. Prod. Res. 25, 324–329. [3] Frezza et al. (2024). Fitoterapia, 175, 105936.