Abstract
Background. Vicia faba is a plant that belongs to the family Fabaceae. Cotyledons of this plant produce compounds called phytoalexins as a result of fungal and bacterial infection or stress factors. The phytoalexins are furanoacetylenic compounds. They include wyerone, wyerol, wyerone acid, their dihydro derivatives, and wyerone epoxide. These compounds have antimicrobial activities mainly against fungi. Objective. The purpose of this study was to elucidate the biogenetic conversion of wyerone and dihydrowyerone to wyerone epoxide in V. faba and to investigate the antibacterial activities of some of these phytoalexins. Materials and Methods. Seeds of Vicia faba were used. Labelled wyerone and dihydrowyerone were obtained by treating CuCl2-induced cotyledons with sodium (2-14C) acetate and separated by TLC and HPLC. Labelled wyerone and dihydrowyerone were then applied to induced bean cotyledons to establish any possible interconversion to wyerone epoxide. Antibacterial activity of wyerone, wyerone acid, and wyerone epoxide was investigated by disc diffusion test against a panel of microorganisms. Zones of inhibition were reported. Results. The radiolabeling studies showed that 12.4% of 14C-wyerone, and 6.01% of 14C-dihydrowyerone were incorporated into wyerone epoxide. This indicates that wyerone epoxide was most probably derived from wyerone and dihydrowyerone. In addition, a new compound, 11-hydroxywyerone was isolated for the first time. Additionally, this study showed that wyerone, wyerone epoxide, and wyerone acid had no antibacterial activity against Gram-negative bacteria but were active against Gram-positive bacteria.
Highlights
Plants were found to have physical and biochemical responses towards pathogen infections. ey evolve coordinate events by relying on their immune system to recognize and actively respond to these infections
Wyerone acid was observed to be the main phytoalexin in leaves and pods, while wyerone was predominant in cotyledons. e accumulation of wyerone and wyerone epoxide in pod endocarp has led to the suggestion that wyerone may act as precursor for wyerone epoxide. is was supported by the observed conversion of wyerone to wyerone epoxide during fractionation of pod tissue [14,15,16]. e biosynthesis of wyerone in Vicia faba was elucidated previously and found to be derived from acetate malonate pathway via fatty acid derivatives [17], and the conversion of wyerone to wyerone acid had been elucidated earlier [18]
In the first feeding experiment using 14C-sodium acetate, the phytoalexin mixture separated by TLC chromatography was detected as deep blue fluorescent band under UV254, with Rf value 0.31. 1HNMR analysis revealed the presence of approximately 8% of 14C-dihydrowyerone in the mixture of 14C-wyerone and 14C-dihydrowyerone. is is in agreement with previous results reported in our laboratory [17, 18]
Summary
Vicia faba is a plant that belongs to the family Fabaceae. Cotyledons of this plant produce compounds called phytoalexins as a result of fungal and bacterial infection or stress factors. E purpose of this study was to elucidate the biogenetic conversion of wyerone and dihydrowyerone to wyerone epoxide in V. faba and to investigate the antibacterial activities of some of these phytoalexins. Antibacterial activity of wyerone, wyerone acid, and wyerone epoxide was investigated by disc diffusion test against a panel of microorganisms. E radiolabeling studies showed that 12.4% of 14C-wyerone, and 6.01% of 14C-dihydrowyerone were incorporated into wyerone epoxide. This study showed that wyerone, wyerone epoxide, and wyerone acid had no antibacterial activity against Gram-negative bacteria but were active against Gram-positive bacteria
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