Constituents of the Vietnamese medicinal plant Orthosiphon stamineus

Front the MeOH extract or the aerial part of Vietnamese Orthosiphon stamine us, five new isopimarane-type diterpenes [orthosiphols F-J (1-5)] and two n ew diterpenes [staminols A (6) and B (7)] with a novel carbon-framework, to which we proposed the name "staminane", and three new highly-oxygenated st aminane-type diterpenes [staminolactones A (8) and B (9) and norstaminol A (10)] were isolated. Moreover, staminolactone A (8) is 8,14-secostaminane-t ype and staminolactone B (9) is 13,14-secostaminane-type, while norstaminol A (10) is 14-norstaminen-type. Together with these new diterpenes, sixteen known compounds were also isolated and identified to be: 7,3',4'-tri-O-met hylluteolin (11), eupatorin (12), sinensetin (13), 5-hydroxy-6,7,3',4'-tetr amethoxyflavone (14), salvigenin (15), ladanein (16), tetramethylscutellare in (17), 6-hydroxy-5,7,4'-trimethoxyflavone (18), vomifoliol (19), aurantia mide acetate (20), rosmarinic acid (21), caffeic acid (22), oleanolic acid (23), ursolic acid (24), betulinic acid (25), and beta -sitosterol (26). Al l the isolated compounds were tested for their cytotoxicity towards highly liver metastatic murine colon 26-L5 carcinoma cells, and the new diterpenes , except for 4, and flavonoids (11, 12, 16, 18) showed cytotoxicity with an ED50 value between 10 and 90 mug/ml.