Paraverrucsins A–F, Antifeedant, and Antiphytopathogenic Polyketides from Rhizospheric Paraphaeosphaeria verruculosa and Induced Bioactivity Enhancement by Coculturing with Host Plant Dendrobium officinale

Six new polyketides named paraverrucsins A-F ( 1 - 6 ) with oxabicyclic and dioxatricyclic skeletons, together with eight known metabolites ( 7 - 14 ), were discovered and isolated from the fermentation medium of Paraphaeosphaeria verruculosa . Paraverrucsin A-C possessed a novel decarboxylated skeleton compared with that of trichocladinols. Their structures were elucidated by extensive spectral analysis and DP4+ calculations. Paraverrucsins B/C and D/E were isolated as a mixture for the mutarotation occurred at C-2. Paraverrucsins B/C, D/E, F/trichocladinol B, 8 , and 9 displayed antifeedant activities against silkworm larvae, with antifeedant index percentages ranging from 62.5 to 93.0%, at a concentration of 50 μg/cm 2 . Among them, Paraverrucsins B/C and 9 had EC 50 values at 13.9 and 18.2 μg/cm 2 . Most compounds showed antifungal activities against phytopathogenic fungi with minimum inhibitory concentration (MIC) values of 16-64 μg/mL. Coculture of P. verruculosa and host plant Dendrobium officinale leads to the enhancement of antifeedant and antiphytopathogenic activities . Compounds 1 , 2 / 3 , 4 / 5 , 6 / 14 were tested for cytotoxicity against five human carcinoma cell lines, HL-60, A549, MCF-7, SW480, and SMMC-7721, while they exhibited selected cytotoxicity against SW480 with inhibition ratios of 32-38% at a concentration of 40 μM.