Inhibitors of Sporangia Formation of Phytophthora capsici from Polygonum capitatum doi.org/10.26538/tjnpr/v2i7.10

Abstract

The genus Phytophthora comprises of nearly 120 pathogenic species which causes both economic and enviormental damage. This study aims to isolate active compounds from natural products for inhibition of sporangia formation of Phytophthora capsici. The ethyl acetate (EtOAc) layer of the methanol (MeOH) extract of Polygonum capitatum exhibited significant activity. The ethyl acetate (EtOAc) fraction was then subjected to bioassay-guided separation and purification to afford five active flavonoids which significantly inhibited sporangia formation on Phytophthora capsici. The structures were elucidated by spectroscopic analysis and comparison of spectroscopic data with those reported. The active compounds were identified as myricetin 7-O-α-Lrhamnopyranoside (1), quercetin 3-O-β-D-glucopyranoside (2), quercetin 4ʹ-O-α-Lrhamnopyranoside (3), quercetin 3-O-(2ʹʹ-galloyl)-α-L-rhamnopyranoside (4), and kaempferol 3- O-α-L-rhamnopyranoside (5). Compounds 1, 2, and 3 were isolated from P. capitatum for the first time. Moreover, the stereo structure of sugar moiety of 3 was corrected by chemical derivatization means. Compounds (1-5) isolated from P. capitatum significantly inhibited sporangia formation of Phytophthora capsici.