Cyathoviridine, a Cytotoxic Metabolite fromCyathostemma viridiflorum

A New Cytotoxic Tetrahydroxanthene-1,3(2H)-dione Derivative from Uvaria cordata and Structure Revision of Valderramenol A

A new tetrahydroxanthene-1,3(2H)-dione derivative (1) was isolated from the leaves of Uvaria cordata collected in Viet Nam. Its structure was elucidated to be a mixture of four tautomers (1a–1d) by a combination of extensive spectroscopic analyses and the theoretical calculation of Gibbs free energies. Compound 1 exhibited moderate cytotoxicity against KB, LNCaP, Hep-G2, MKN-7, SW-480, HL-60, and SK-Mel-2 cancer cell lines with IC50 values ranging from 25.92 ± 2.33 to 44.29 ± 4.36 μg/mL. In addition, the previously reported structure of valderramenol A has been revised to 1a/1b.

Tetrahydroxanthene-1,3(2H)-dione derivatives from Uvaria valderramensis

Two tetrahydroxanthene-1,3(2H)-dione metabolites, valderramenols A (1) and B (2), were isolated from the Philippine endemic Annonaceous species Uvaria valderramensis. Planar structures of the rac-xanthene-1,3-(2H)-diones 1 and 2 were established by MS and NMR measurements. Their enantiomers were separated by chiral HPLC, and the absolute configurations of the separated enantiomers were determined by comparison of the HPLC-ECD spectra with computed TDDFT-generated spectra. A TDDFT-ECD study of the known grandiuvarone (3) allowed the revision of its absolute configuration as S. Compound 1 showed antitubercular activity (MIC 10 μg/mL), while 3 and 4 had weaker activities (MIC 32 μg/mL). Oxepinone 3 exhibited cytotoxic activity against KB-562, a chronic myeloid leukemia cell line.

Dihydrochalcones with antiinflammatory activity from leaves and twigs of Cyathostemma argenteum

A new dihydrochalcone derivative, 4',6'-dihydroxy-2',4-dimethoxy-5'-(2''-hydroxybenzyl)dihydrochalcone (1) and one known dihydrochalcone, 4',6'-dihydroxy-2',4- dimethoxydihydrochalcone (2) were isolated from leaves and twigs of Cyathostemma argenteum. Their structures were established by spectral methods, mainly 2D NMR spectroscopic techniques, which involved combined applications of DEPT, COSY, HMQC and HMBC. The molecular structure of 1 was also confirmed by single crystal X-ray diffraction. The test compounds 1 and 2 displayed significant inhibitory activity at a dose of 1 mg/ear on edema formation at all determination times, with similar intensity as phenylbutazone.