| Summary: | Three new dimeric abietane-type diterpenoids, abieta-6,8,11,13-tetraen-12-yl 12-hydroxyabieta-8,11,13-trien-7α-yl peroxide (<b>1</b>), abieta-6,8,11,13-tetraen-12-yl 12-hydroxyabieta-8,11,13-trien-7β-yl peroxide (<b>2</b>), and 12-hydroxyabieta-8,11,13-trien-7β-yl 7-oxoabieta-5,8,11,13-tetraen-12-yl peroxide (<b>3</b>), together with four known abietane-type diterpenoids (<b>4</b>−<b>7</b>) were isolated from the methanol extract of the bark of <i>Cryptomeria japonica</i>. Their structures were elucidated on the basis of spectroscopic analysis and comparison of NMR data with those of known analogues. At a concentration of 50 μM, compounds <b>1</b>, <b>2</b>, and <b>3</b> showed 26.2%, 23.6%, and 35.7% inhibition towards xanthine oxidase enzyme, respectively. In addition, compound <b>3</b> also showed 24.9% inhibition toward angiotensin-converting enzyme (ACE).
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