Abietane diterpenoids from Sideritis montana L. and their antiproliferative activity.

The present study aimed at the phytochemical and pharmacological investigation of Sideritis montana L. (Lamiaceae). Two new abietane diterpenes [sideritins A (1) and B (2)] were isolated from the methanol extract of the plant. Six known compounds [pomiferin E (3), 9α,13α-epi-dioxyabiet-8(14)-en-18-ol (4), paulownin (5), 6-methoxysakuranetin (6), 3-oxo-α-ionol (7) and 4-allyl-2,6-dimethoxyphenol glucoside (8)] were also obtained from the plant. The structures were determined by means of HREIMS and NMR experiments. The antiproliferative effect of the isolated compounds was investigated on human cancer cell lines (HeLa, SiHa and C33A) at 10 and 30μM concentrations, using the MTT assay. The results demonstrated that pomiferin E (3) and 6-methoxysakuranetin (6) displayed considerable activity [inhibition (%)±SEM: 46.93±2.35 on HeLa (pomiferin E), and 51.52±2.45 on C33A (6-methoxysakuranetin)] at 30μM concentration.