Potential Biochemical Properties of Endemic Onosma mutabilis

The Onosma L. (Lithospermae, Boraginaceae) genus contains many plant species with therapeutic properties due to its rich phytochemicals. Onosma mutabilis Boiss. & Hausskn. ex Boiss. (O. mutabilis) is the species for which there is not enough information on its characteristics. Objective: The total phenolic content, antioxidant activity, possible bioactive compounds, and antibacterial activities of ethanolic extracts of leaf, stem, root, and flower parts of endemic O. mutabilis were investigated. Conclusions: The total phenolic content of all O. mutabilis extracts was in the range of 9.2–31 mg gallic acid equivalent (GAE)/g of extract. According to the results of antioxidant activity, the IC50 antioxidant capacity values determined by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method were between 4.39–29 μg/mL, while the equivalent trolox antioxidant activity determined by the cupric reducing antioxidant values (CUPRAC) was 0.45–0.78 mmol of trolox equivalents (TE)/g of extract. Bioactive compounds have been analysed using gas chromatography coupled with mass spectrometry (GC/MS) and were found to contain 29 different chemical components. All plant extracts tested showed effective antibacterial activity against A. baumannii (ATCC 02026) (62.5 μg/mL MIC value) when compared to the reference drug Ampicillin (125 μg/mL).