Antimicrobial and cytotoxic abietane diterpenoids from the roots of Meriandera benghalensis (Roxb.) Benth.

Four abietane diterpenoids were isolated from the methanolic extract of the roots of Meriandera benghalensis and tested for their biological activity. Cryptotanshinone (2) and 17-hydroxycryptotanshinone (4) are known metabolites however the occurrence of tanshinone IIA (1) and przewaquinone A (3) from Meriandera benghalensis is reported for the first time. The four diterpenoids were identified by MS and one- and two dimensional NMR experiments. The isolated compounds were tested for their in vitro antiproliferative activity against three human cancer cell lines (a lung cancer (A-427), a urinary bladder cancer (5637) and a breast cancer (MCF-7) cell line) and for their antibacterial effect against three Gram-positive bacterial strains. All four abietanes showed potent cytotoxic effect against all cancer cell lines (IC50 between 1 and 8 microM) as well as antibacterial effect against the bacteria tested (MIC values between 33 and 70 microM).