Secoisopimaranes from Salvia elegans Vahl leaves as antibacterial agents against Staphylococcus aureus

The genus Salvia contains around 1000 species and is primarily known to produce caffeic acid polymers and diterpenes. Of the bi- and tricyclic classes of diterpenes found in Salvia, isopimaranes are the least represented. The bio-guided metabolomic analysis of the leaves of Salvia elegans Vahl revealed the occurrences of three secoisopimaranes (1-3), of which the known 3,4-secoisopimara-7,15-dien-3-oic acid was the most abundant and showed potent antimicrobial activity against Staphylococcus aureus with a MIC = 15.6 µg/mL (51.6 µM). All three diterpenes were detected in domesticated and wild specimens of the closely related species Salvia cinnabarina M.Martens & Galeotti, but not in other species reportedly to be closely related to S. elegans. Diterpenoids from Salvia are an interesting group of biologically active molecules and their distribution within the genus justifies further study.