Integracin A

Two new polyketides, cytospyrone (1), cytospomarin (2), together with three known metabolites dimethoxyphtalide (3), integracin A (4) and integracin B (5), were isolated from the culture of Cytospora sp. from the Chinese mangrove Ceriops tagal. Their structures were elucidated by extensive spectroscopic analyses and time dependent density functional theory (TDDFT), calculation of electronic circular dichroism (ECD) and optical rotation (OR) data. Compound 2 displayed weak inhibitory activity against Escherichia coli GIM1.201 (minimum inhibitory concentration (MIC) value of 0.35 mM). Compounds 4 and 5 displayed significant cytotoxicity against human cancer cell line HepG2 (IC50 values of 5.98 ± 0.12 µM and 9.97 ± 0.06 µM, respectively), more potent than the positive control 5-fluorouracil (IC50 value of 43.50 ± 3.69 µM).

Integracins A (1) and B (2), potent HIV-1 integrase inhibitors, and 15'-dehydroxy-integracin B (3) were isolated for the first time from Chinese mangrove plant Sonneratia hainanensis. Their absolute configurations were determined by the Mosher's method and specific rotation analysis of alcohols (6 and 7) obtained from integracin A in two steps and by chemical correlation. Integracin A (1) also exhibited significant cytotoxicity against the tumor cell lines HepG2 and NCI-H460 with both 100% inhibitions at 25 µg/ml.

Japanese oak wilt (JOW) is a tree disease caused by the fungus Raffaelea quercivora, which is vectored by the ambrosia beetle, Platypus quercivorus. In a screening study of the inhibitory active compounds from fungi, a new cytosporone analogue, compound 1, was isolated from the endophytic fungus Cytospora sp. TT-10 isolated from Japanese oak, together with the known compounds, integracin A (2), cytosporones N (3) and A (4). Their structures were determined by extensive 1D- and 2D-NMR spectroscopic and mass spectral analyses. Compound 1 was identified as 4,5-dihydroxy-3-heptylphthalide and named cytosporone E. Compounds 2 and 3 showed antimicrobial activity against Raffaelea quercivora.