Formanilides from the culture broth of Perenniporia fraxinea

A new formanilide dimer, fraxinin (1), and three known formanilides (2‒4) were isolated from the culture broth of Perenniporia fraxinea using silica gel and Sephadex LH-20 column chromatographies, medium-pressure liquid chromatography (MPLC), and preparative HPLC. The structures of these compounds were determined by spectroscopic methods, such as NMR and mass analysis, and by comparison of the spectra with previously reported data. The free radical scavenging activities of the isolated compounds were assessed using 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. Compounds 1‒3 exhibited ABTS radical scavenging activity with IC₅₀ values in the range of 57.2–250.2 μM. Compounds 2 and 4 marginally reduced disease incidence of powdery mildew with a control value of 42% at 1.0 mg ml⁻¹ in cucumber leaf disk assay.