Three xanthone derivatives, gambogic acid, isogambogic acid and isomorellinol, were isolated from the dried latex of Gurcinia hunburyi. Two of them, isogambogic acid and isomorellinol, are new. Determinations of the structures and stereochernistry were achieved independently by a series of NMR experiments including COSY, ROESY, HMQC, HMBC and selective INEPT. Isolation of isomorellinol from G. hnburyi provided important chemical evidence to link this species to G. morella. The presence of gambogic acid and isogambogic acid, however, demonstrated the difference between these two species. Cytotoxic evaluation of these isoiates revealed that al1 three were active against KB and drug-resistant K B V l cell lines.
Five ingenane derivatives, 3-O-n-(deca-2,4,6-trienoyl)-16-O-[(Z)-2-methyl-2-butenoyl]-16-hydroxyingenol (1), 3-O-[(Z)-2-methyl-2-butenoyl]-5,16,20-O-triacetyl-16-hydroxyingenol (2), 3-O-[(Z)-2-methyl-2-butenoyl]-16,20-O-diacetyl-16-hydroxyingenol (3), 3-O-[(Z)-2-methyl-2-butenoyl]-20-O-acetylingenol (4), and 3-O-[(Z)-2-methyl-2-butenoyl]-16-O-acetyl-20-deoxy-16-hydroxyingenol (5) were isolated with a new procedure that uses droplet counter-current chromatography, from a dermatitis-producing fraction of the latex of Euphorbia hermentiana Lem. The structures of the new compounds 2,3, and 5 were established by the interpretation of their spectroscopic data and those of their hydrolytic and acetylated derivatives.
The feeding of (13)C- and (2)H-enriched methionine to Streptomyces staurosporeus established that the methyl carbon and proton source of both the 3'-O- and 4'-N-methyl groups of staurosporine (1) was methionine and that all three methyl protons from methionine were retained on 1. In the presence of the methyltransferase inhibitor, sinefungin, the biosynthesis of staurosporine was blocked at the last step, O-methylation. An intermediate, 3'-demethoxy-3'-hydroxystaurosporine (2), was efficiently accumulated in the medium. Other general methyltransferase inhibitors failed to produce any other staurosporine intermediates or analogues.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.