Fatty acids composition, physicochemical characterization, and antioxidant potential of Stachys germanica ssp. cordegira Briq seed oil

Abstract

• Seeds of Stachys germanica ssp. cordigera yield 27% oil. • The oil is rich in unsaturated fatty acids, mainly linoleic and oleic acids • It contains 6.47% 6-octadecynoic acid, a chemotaxonomic marker of the Stachys genus . • Physicochemical analysis shows a high saponification value, high iodine value, and low acidity and peroxide value. • The oil shows strong antioxidant activity (62% DPPH scavenging; 23.6 mg GAE/g phenolics). This study aimed to provide the first comprehensive characterization of the seed oil of Stachys germanica ssp. cordigera (Lamiaceae), an underexplored species, with a focus on its chemical composition, physicochemical parameters, and antioxidant potential. The oil was analyzed by GC-MS to determine fatty acid methyl ester composition, and physicochemical parameters were measured according to standard methods. Antioxidant activity was assessed using DPPH, total antioxidant capacity (TAC), and ferric reducing antioxidant power (FRAP) assays. The oil was rich in unsaturated fatty acids, particularly linoleic (35.0%) and oleic acids (31.1%), and uniquely contained 6-octadecynoic acid (6.5%), a rare acetylenic fatty acid with reported bioactivities. Physicochemical values (acid value 3 mg KOH/g; saponification value 188.8 mg KOH/g; iodine value 112 g I 2 /100g; peroxide value 13 meq O 2 /kg) were within Codex Alimentarius standards. Antioxidant testing showed 62% DPPH inhibition (IC 50 = 1.10 ± 0.25 mg/mL), TAC = 50.4 ± 1.7 mg AAE/g, and FRAP = 45.2 ± 1.8 µmol Fe 2+ /g at 1 mg/mL. Antioxidant activity was moderate compared to BHT but comparable to several natural edible oils. This work provides the first detailed report of Stachys germanica ssp. cordigera seed oil, highlighting its distinctive composition and antioxidant properties. While its acetylenic fatty acid content underscores chemotaxonomic and potential bioactive significance, further studies are required to confirm in vivo activities, assess toxicity, and evaluate scalability before industrial applications can be considered.