Chemophenetically relevant iridoids and phenolics from Betonica and Stachys (Lamioideae, Lamiaceae)

Betonica L. and Stachys L. are closely related genera within the Lamiaceae family, yet comparative phytochemical data on their secondary metabolites remain limited. In this study, we investigated and compared the iridoid and phenolic profiles of selected species from both genera to better understand their secondary metabolite diversity. RP-UHPLC-DAD-HRMS analyses of the methanolic extracts of three Betonica species (B. alopecuros L., B. macrantha K.Koch, and B. officinalis L.) and three Stachys species [S. arvensis (L.) L., S. byzantina K.Koch, and S. sylvatica L.] revealed pronounced differences in their secondary metabolite profiles. Chlorogenic acid, harpagide, and martynoside were detected in all investigated species. The iridoid glycoside allobetonicoside was present exclusively in the examined Betonica species, while flavone glycosides showed genus-specific patterns: isoscutellarein and hypolaetin derivatives occurred only in Stachys, whereas tricin and tricetin glucuronides were restricted to Betonica. These differences highlight distinct secondary metabolite profiles between the two genera. Allobetonicoside, tricin 7-O-glucuronide, and tricetin 3′,4′,5′-trimethyl ether-7-O-glucuronide might therefore serve as chemophenetic markers for the genus Betonica, while the presence of hypolaetin 4′-methylether 7-O-[6‴-acetylallosyl (1→2) glucoside] and isoscutellarein 7-O-[6‴-acetylallosyl (1→2) glucoside] exclusively in Stachys supports their value as marker compounds for this genus.

Tricetin 3′,4′,5′-trimethyl ether-7-O-glucuronide, which had previously only been reported from Artemisia frigida Willd. (Asteraceae) as friginoside A, was isolated from B. officinalis. A detailed analysis of the methanolic extract of B. officinalis confirmed the presence of known compounds, including the phenylpropanoids verbascoside, forsythoside B, leucosceptoside B, martynoside, betonyoside F, and stachysoside B; the iridoids harpagide, 8-O-acetylharpagide, and allobetonicoside; and the flavonoid isoorientin. These findings might contribute to chemophentically characterize the genera Betonica and Stachys.