Platelet aggregation inhibitors in a Bhutanese medicinal plant, shug chher

The 90% methanol-soluble fraction of a Bhutanese medicinal plant, Shug Chher, exhibited inhibition of platelet aggregation induced by platelet activating factor. Bioassay-directed fractionation led to the isolation of four new labdane diterpenoids, 3 alpha, 15-dihydroxy-labda-8(17), 13E-diene (5), 3 alpha-hydroxy-labda-8(17), 13E-dien-15-oic acid (6), 3 alpha-hydroxy-labda-8(17), 12E, 14-trien-19-oic acid (7), and 3 alpha-acetoxyisocupressic acid (8) and four known diterpenoids, manool (1), 3 alpha-hydroxymanool (2), 3 alpha-hydroxy-12, 13E-biformene (3), and isocupressic acid (4). The structures of the new compounds were determined spectroscopically. Compounds 2, 3, and 5 inhibited platelet aggregation.