Two new dimeric abietanoid peroxides with xanthine oxidase and ACE inhibitory activities from the bark of Cryptomeria japonica

Two new dimeric abietane-type diterpenoids, 12-hydroxyabieta-8,11,13-trien-7-α-yl 7-oxoabieta-8,11,13-trien-12-yl peroxide (trivial name japonicinol C, 1) and 12-hydroxyabieta-8,11,13-trien-7-α-yl 7-oxoabieta-5,8,11,13-tetraen-12-yl peroxide (trivial name japonicinol D, 3), together with two known dimeric abietane-type diterpenoids, obtusanol A (2) and 7-α-(2-butoxyethoxy)-12-hydroxyabieta-6-yl 6,7-dehydroabieta-8,11,13-trien-12-yl ether (4), were isolated from the methanol extract of the bark of Cryptomeria japonica. Their structures were established by mean of spectroscopic analysis and comparison of NMR data with those of known analogues. At a concentration of 50 μM, compounds 1–4 inhibited xanthine oxidase activity by 29.8, 39.3, 27.1, and 14.7 %, respectively. In addition, compounds 1 and 4 also showed 13.9 and 20.5 % inhibition toward angiotensin-converting enzyme (ACE), respectively.