Three new polyprenylated benzophenone derivatives named burlemarxiones G-I (1-3) were isolated from C. burle-marxii trunks (compound 1) and leaves (compounds 2 and 3), along with the known compound burlemarxione F. Burlemarxione G (1) was isolated after methylation with diazomethane and it is the keto-enol tautomeric pair of burlemarxione F. Burlemarxione H (2) derives from burlemarxiones F and G, but it has additional rings due to cyclization of the prenyl group attached to C-5 that establishes new single bonds between C-1 and C-23, as well as, between C-24 and C-29. Burlemarxione I (3) has two additional cyclizations: the first encompasses the cyclization of the former isopentenyl group into an 11,11-dimethyl-six-membered ring, whereas the second produces additional rings due to the cyclization of the prenyl group attached to C-5 that establishes new single bonds between C-1 and C-23, as well as, between C-24 and C-29. All three compounds showed moderate anti-glioma activity. These results show that C. burle-marxii is an important source of sophisticated polyprenylated benzophenone derivatives.
Keywords: Anti-glioma; Chemotaxonomic markers; Clusiaceae; Cytotoxic; Polycyclic polyprenylated acylphloroglucinols.
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