Abstract:

Fungus Aspergillus sp., which was isolated from soft coral Sarcophyton tortuosum, was cultured in the GPY medium containing glucose 10 g/L, peptone 5 g/L, yeast extract 2 g/L, sea water 1 L, at pH=7.5. Four compounds, 3,6-diisobutyl-2(1H)-pyrazinone(1), 3-isobutyl-6-(1-hydroxy-2-methylpropyl)-2(1H)-pyrazinone(2), 3-methoxy-4-methyl-2,4-dien-pentanoic acid(3) and penicillic acid(4) were obtained from the AcOEt extract of the culture broth. Their structures were elucidated mainly based on the NMR, HR-EI-MS and X-ray single crystal diffraction experimental data. Compound 3 is a new compound. Compound 1 was previously proposed to be the tautomer of flavacol(3,6-diisobutylpyrazin-2-ol, 5). However, the evaluation of the NMR and X-ray single crystal diffraction experimental data permitted us to propose that compound 1 existed as amide form instead of tautomers. Compound 1 is stable both in solution and crystal due to strong intermolecular hydrogen bonds. Incidentally supplying anthracenone to the GPY medium with a dose of 100 mg/L, the yield of penicillic acid(4) in the culture broth of the strain Aspergillus sp. was increased dramatically from 6 mg/L to 57 mg/L.

Key words: Aspergillus sp.; 3,6-diisobutyl-2(1H)-pyrazinone; Penicillic acid; Flavacol