Indole-diterpenoids with anti-H1N1 activity from the aciduric fungus Penicillium camemberti OUCMDZ-1492

An aciduric Fungal strain, Penicillium camemberti OUCMDZ-1492, was isolated from an acidic marine niche, mangrove soil and mud, around the roots of Rhizophora apiculata. Six new indole-diterpenoids (1-6), along with five known analogues, emindole SB (7), 21-isopentenylpaxilline (8), paspaline (9), paxilline (10), and dehydroxypaxilline (11), were isolated from the fermentation broth of P. camemberti OUCMDZ-1492 grown at pH 5.0. On the basis of spectroscopic analyses, CD spectra, quantum ECD calculations, and chemical methods, new structures 1-6 were established as 3-deoxo-4b-deoxypaxilline, 4a-demethylpaspaline-4a-carboxylic acid, 4a-demethylpaspaline-3,4,4a-triol, 2'-hydroxypaxilline, 9,10-diisopentenylpaxilline, and (6S,7R,10E,14E)-16-(1H-indol-3-yl)-2,6,10,14-tetramethylhexadeca-2,10,14-triene-6,7-diol, respectively. Compounds 1-3 and 5-10 exhibited significant activity against the H1N1 virus with IC50 values of 28.3, 38.9, 32.2, 73.3, 34.1, 26.2, 6.6, 77.9, and 17.7 μM, respectively. The results showed that 3-oxo, 4b-hydroxy, and 9-isopentenyl substitutions tend to increase the anti-H1N1 activity of hexacyclic indole-diterpenoids.