Isolation and Antifungal Activity of 4-Phenyl-3-Butenoic Acid from Streptomyces koyangensis Strain VK-A60

An antifungal compound was isolated from the culture broth of Streptomyces koyangensis strain VK-A60 using various chromatographic procedures. On the basis of the high-resolution EI-mass and 1H and 13C NMR data, the compound was identified as 4-phenyl-3-butenoic acid. Colletotrichum orbiculare, Magnaporthe grisea, and Pythium ultimum were most sensitive to 4-phenyl-3-butenoic acid. Strong inhibitory effects of 4-phenyl-3-butenoic acid also were found against Pectobacterium carotovorum subsp. carotovorum and Ralstonia solanacearum. 4-Phenyl-3-butenoic acid effectively suppressed the development of M. grisea on rice leaves at the concentration of more than 10 μg/mL, and the protective activity was in general similar to that of the commercial fungicide tricyclazole. Treatment with 100 μg/mL of 4-phenyl-3-butenoic acid also effectively inhibited the anthracnose development on cucumber plants, although its in vivo efficacy was somewhat less effective than that of the commercial fungicide chlorothalonil. Keywords: Streptomyces koyangensis; 4-phenyl-3-butenoic acid; antifungal activity; cucumber anthracnose; rice blast