Temporal Phenolic Profile and Bioactivity of Endemic Salvia transsylvanica (Transylvanian Sage) During Flowering

Salvia transsylvanica, an endemic Romanian sage, remains understudied despite co-occurrence with validated medicinal Salvia species. In this study, lfeaves and flowers were harvested weekly during flowering (May and June) and subjected to classical hydroethanolic extraction, HPLC–DAD–ESI/MSn profiling, in vitro antioxidant assays (ABTS, DPPH, FRAP), and enzyme-inhibitory screening, with multivariate analysis correlating compositional patterns with bioactivity. Rosmarinic acid dominated the phenolic profile (68.6 mg/g maximum in week 4), alongside salvianolic acids (salvianolic acid K isomers) and flavonoid glycosides (luteolin, apigenin, and hispidulin hexosides). Leaf extracts displayed higher ABTS/DPPH scavenging (higher phenolic acid content), while flowers showed superior FRAP and α-glucosidase inhibition (IC50 84–143 μg/mL, higher flavonoids), with maximal values being identified during week 4. S. transsylvanica offers complementary antioxidant profiles to commercial sages, warranting future in vivo validation for therapeutic applications.