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The microbiological transformation of the triterpene nigranoic acid (3,4-secocycloarta-4(28),24(Z)-diene-3,26-dioic acid) (1) to 3,4-secocycloarta-4(28),17(20),24(Z)-triene-7β-hydroxy-16β,26-lactone-3-oic acid (2) and 3,4-secocycloarta-4(28),17(20)(Z),24(Z)-triene-7β-hydroxy-16β-methoxy-3,26-dioic acid (3) by the freshwater fungus Dictyosporium heptasporum YMF1.01213 has been demonstrated. The structures of the biotransformation products were determined by spectroscopic and MS analyses. Compound 2, characterized by the presence of a formed C-16/C-26 ester bridge, provided a novel nine-membered lactone ring structural skeleton for 3,4-secocycloartane triterpenoid derivatives. In addition, Compounds 1–3 exhibited weak anti-HIV activity in vitro. Compounds 2 and 3 were reported for the first time as natural product derivatives. [ABSTRACT FROM AUTHOR]

Three new naphthoquinones, astropaquinones A-C (1-3), were isolated from cultures of the freshwater fungus Astrosphaeriella papuana YMF 1.01181, together with the known compound, 6-hydroxy-2,4-dimethoxy-7-methylanthraquinone (4). The structures of the compounds were settled mainly by interpretation of their 1D and 2D NMR spectra. Astropaquinone B (2) and C (3) were found to possess a rare pyranonaphthoquinone skeleton containing a lactol ring. Furthermore, compounds 1-4 showed moderate antagonistic activity against nine fungi and four bacterial strains., (Georg Thieme Verlag KG Stuttgart, New York.)