Phytochemical profiling and evaluation of antioxidant, antimicrobial, and cytotoxic activities of endemic <i>Onosma angustissima</i>

This study reports the first comprehensive phytochemical and biological evaluation of ethanol and supercritical CO₂ extracts from the aerial parts of the endemic <i>Onosma angustissima</i> (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%), <i>β</i>-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 <i>Enterococcus faecalis</i> (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 <i>O. angustissima</i>, traditionally used against inflammation and infections, as a promising natural source of antioxidant, antimicrobial, and anticancer agents, particularly in its supercritical CO₂ extract form.