Chemical Profiling and Multi‐Bioactive Potential of Onosma nigricaulis

ABSTRACT In Turkish folk medicine, Onosma species are used to treat wounds, burns, and ulcers. This study investigated the chemical composition and biological activities of ethanolic (EE) and petroleum ether (PEE) extracts from the endemic Onosma nigricaulis (Boraginaceae). GC–MS analysis identified 25 and 21 compounds in EE and PEE, representing over 90% of total extract content. The major constituents of EE were palmitic acid (25.84%), linolenic acid (19.36%), and γ‐sitosterol (11.25%), while PEE mainly contained linolenyl alcohol (16.48%), γ‐sitosterol (15.50%), and palmitic acid (14.69%). FT‐IR spectra confirmed the presence of hydroxyl, carbonyl, and alkyl functional groups, supporting the GC–MS results. Antioxidant potential was evaluated using DPPH andreducing power assays, where EE exhibited stronger activity, achieving 72.53% inhibition at 800 µg/mL. Both extracts showed antimicrobial activity against Escherichia coli , Enterococcus faecalis , and Candida albicans , with EE displaying lower MIC values (5.09–6.09 mg/mL). Cytotoxicity assessment via MTT assay revealed significant dose‐dependent effects, with IC 50 values of 35.38 µg/mL for A549 and 57.30 µg/mL for DU‐145 cells. These results highlight O. nigricaulis as a promising natural source of bioactive compounds with antioxidant, antimicrobial, and anticancer potential.