Phytochemical profiling and evaluation of antioxidant, antimicrobial, and cytotoxic activities of endemic Onosma angustissima

This study reports the first comprehensive phytochemical and biological evaluation of ethanol and supercritical CO2 extracts from the aerial parts of the endemic Onosma angustissima (Boraginaceae) native to the Irano-Turanian region. Gas chromatography–mass spectrometry (GC–MS) identified 21 compounds in the ethanol extract, with linoleic acid (10.62%), phytol (8.18%), β-sitosterol (6.45%), and palmitic acid (5.63%) as major constituents. Supercritical CO2 extraction (ScCO2-E) under different pressures (100 and 150 bar) yielded pressure-dependent variations in key flavonoids and phenolics, including naringenin, rutin, luteolin, and cyranoside, as revealed by LC–MS/MS. Antioxidant activity assessed by DPPH and reducing power assays showed that the ethanol extract had 60.29% DPPH scavenging activity, while the 150-bar extract (O150) displayed stronger potency (IC50 < 200 µg/mL). Both extracts exhibited antimicrobial effects, notably against Enterococcus faecalis (MIC = 62.5 µg/mL for ScCO2 extracts), and cytotoxicity toward MCF-7 breast cancer cells, with O150 reducing cell viability to 49% at 800 µg/mL. The results highlight O. angustissima, traditionally used against inflammation and infections, as a promising natural source of antioxidant, antimicrobial, and anticancer agents, particularly in its supercritical CO2 extract form.