Effect of polyacetylenic acids from Prunella vulgaris on various plant pathogens

Abstract

This study is aiming at characterizing antifungal substances from the methanol extract of Prunella vulgaris and at investigating those substances' antifungal and antioomycete activities against various plant pathogens. Two polyacetylenic acids were isolated from P. vulgaris as active principles and identified as octadeca-9,11,13-triynoic acid and trans-octadec-13-ene-9,11-diynoic acid. These two compounds inhibited the growth of Magnaporthe oryzae, Rhizoctonia solani, Phytophthora infestans, Sclerotinia sclerotiorum, Fusarium oxysporum f. sp. raphani, and Phytophthora capsici. In addition, these two compounds and the wettable powder-type formulation of an n-hexane fraction of P. vulgaris significantly suppressed the development of rice blast, tomato late blight, wheat leaf rust, and red pepper anthracnose. These data show that the extract of P. vulgaris and two polyacetylenic acids possess antifungal and antioomycete activities against a broad spectrum of tested plant pathogens. This is the first report on the occurrence of octadeca-9,11,13-triynoic acid and trans-octadec-13-ene-9,11-diynoic acid in P. vulgaris and their efficacy against plant diseases. The crude extract containing the two polyacetylenic acids can be used as a natural fungicide for the control of various plant diseases.