Nigirpexin E, a new azaphilone derivative with anti-tobacco mosaic virus activity from soil-derived fungus Trichoderma afroharzianum LTR-2

A new compound classified as one new azaphilone derivative, nigirpexin E (1), was obtained from the soil-derived fungus Trichoderma afroharzianum LTR-2, together with seven known compounds (2-8). The structures of 1-8 were determined by their HRESIMS, optical rotation, and NMR spectroscopic data. The absolute configuration of nigirpexin E (1) was determined on the basis of comparisons of experimental and theoretically calculated ECD spectra. Compound 3 was firstly isolated from Trichoderma. Bioactivities of the isolated compounds were assayed their anti-tobacco mosaic virus (anti-TMV) activities. The results showed that compound 1 exhibited significant inactivation effect against TMV with an inhibition rate of 67.25% (0.5 mg ml-1), which was higher than that of positive control ribavirin (56.74%). This is the first report of the anti-TMV activity of azaphilone derivatives.