New guaianolides and xanthine oxidase inhibitory flavonols from Ajania fruticulosa

Two new guaianolides (1 and 2) were isolated from the aerial parts of Ajani a fruticulosa along with a triterpene (alpha-amyrin), two plant sterols (be ta-sitosterol and daucosterol), four flavonols [santin (3), axillarin (4), centaureidin, and 5,7,4'-trihydroxy-3,3'-dimethoxyflavone], and five sesqui terpenes [ketoplenolide B, 9 beta-hydroxyeudesma-4,11(13)-dien-12-oic acid, 9 beta-acetoxyeudesma-4,11(13)-dien-12-oic acid, 1 alpha,4 alpha,10 alpha- trihydroxy-9 alpha-angeloyloxyguaia-2,11(13)-dien-12,6 alpha-olide, and 3 b eta,4 alpha-dihydroxyguaia-11(13),10(14)-dien-12,6 alpha-olide]. The struct ures of the new guaianolides were established as 1 alpha-hydroperoxy-4 beta ,8 alpha,10 alpha,13-tetrahydroxyguaia-2-en-12,6 alpha-olide (1) and 1 alph a-hydroperoxy-4 alpha,10 alpha-dihydroxy-9 alpha-angeloyloxyguaia-2,11(13)- dien-12,6 alpha-olide (2), respectively. Xanthine oxidase assays of all iso lates revealed that santin (3) and axillarin (4) inhibited the enzyme with IC50 values of 36.5 and 36.0 mu M (that of allopurinol used as a positive c ontrol in the study was 24.2 mu M), respectively.