Aromatase inhibitory activities of standishinal and the diterpenoids from the bark of Thuja standishii

The absolute stereostructure of a novel skeletal diterpene, standishinal (1), from the bark of Thuja standishii was confirmed by X-ray crystallographic analyses of 1 and its p-bromobenzoate derivative. Aromatase inhibitory activities of standishinal, eight known diterpenes, totarol, 12-methoxyabieta-8,11,13-trien-11-ol, 12-hydroxy-6,7-seco-abieta-8,11,13-triene-6,7-dial, trans-communic acid, labda-8(17),13-dien-12R,15-olid-19-oic acid, 12S-hydroxylabda-8(17),13(16),14-trien-19-oic acid, 13-oxo-15,16-dinorlabda-8(17),11E-dien-19-oic acid and 14-oxo-15-norlabda-8 (17),12E-dien-19-oic acid from the plant, and four synthetic analogs were evaluated using a recombinant human aromatase. Among them, standishinal and its diacetate derivative had significant inhibitory activities.