Phytochemical analysis in some Iranian Scutellaria spp., a chemotaxonomic approach

Species of the genus Scutellaria (Lamiaceae) are widely distributed and have long been used in traditional medicine for the treatment of gastrointestinal, cardiovascular, neurological, and respiratory disorders. However, comparative chemotaxonomic assessments of Iranian Scutellaria taxa remain limited. In this study, we investigated the phytochemical diversity and chemotaxonomic relationships among six Iranian Scutellaria species (including Scutellaria pinnatifida A. Hamilt., Sc. araxensis Grossh., Sc. bornmulleri Hausskn. ex Bornm., Sc. tomentosa Bertol., Sc. theobromina Rech F., and Sc. sosnowskyi Grossh.) collected from natural habitats in Northwestern Iran, using integrated analyses of essential oils, phenolic compounds and fatty acid profiles. Substantial interspecific variation was detected across all metabolite classes, demonstrating pronounced biochemical heterogeneity within the genus. Essential oil analysis showed that α-pinene was most abundant in Sc. araxensis (21.64%) and Sc. tomentosa (14.43%), whereas trans-caryophyllene predominated in Sc. bornmuelleri (25.68%) and Sc. theobromina (25.07%). Germacrene D was the principal constituent of Sc. pinnatifida (40.16%), while Sc. tomentosa exhibited the highest caryophyllene oxide content (19.33%). High performance liquid chromatography (HPLC) profiling further revealed marked differences in phenolic composition, with gallic acid ranging from 11.59 to 31.54 mg/100 g DW, caffeic acid from 2.32 to 18.93 mg/100 g DW, chlorogenic acid from 1.10 to 23.96 mg/100 g DW, and rutin from 10.13 to 22.23 mg/100 g DW. Fatty acid composition also showed clear species-specific patterns: palmitic acid was highest in Sc. bornmuelleri (19.62%) and Sc. araxensis (19.40%), whereas oleic acid reached maximum levels in Sc. sosnowskyi (48.29%) and Sc. tomentosa (47.31%). Linoleic acid was most abundant in Sc. tomentosa (34.36%) and Sc. sosnowskyi (32.48%). Hierarchical clustering analysis (HCA) separated the taxa into three distinct groups, while principal component analysis (PCA) confirmed clear biochemical differentiation, with the first two components explaining most of the total variance. The strong concordance between both multivariate approaches supports the robustness of the inferred relationships. Overall, these findings demonstrate that integrated metabolite profiling is a powerful chemotaxonomic tool for species discrimination, biodiversity evaluation, and identification of promising Scutellaria germplasm for medicinal and industrial exploitation.