Phytochemical study of Salvia leeriifolia roots: rearranged abietane diterpenoids with antiprotozoal activity

Phytochemical investigation of the lipophilic extract of the roots of Salvia leriifolia resulted in the isolation of the new rearranged abietane diterpenoids leriifoliol (1) and leriifolione (2), together with 10 known diterpenoids. Structure elucidations were performed via extensive NMR and HRESIMS data, and the absolute configurations of compounds 1 and 3-5 were established by evaluation of experimental and calculated ECD spectra. The antiplasmodial activity of the new isolates was assayed against Trypanosoma brucei rhodesiense, T. cruzi, Plasmodium falciparum, and Leishmania donovani and also toxicity against rat myoblast (L6) cells. Compound 1 displayed antimalarial and low cytotoxic activity with IC50 values of 0.4 and 33.6 μM, respectively, and a selectivity index of 84. Compound 2 displayed activity against T. brucei, T. cruzi, and L. donovani, with IC50 values of 1.0, 4.6, and 1.0 μM, respectively. Putative biosynthetic pathways toward the formation of 1, 2, and 3 are proposed. Leriifoliol (1) is the first 20- nor-9,10- seco-abietane, while 2 exhibits an uncommon 6-6-5 fused-ring system.