Phytogrowth-inhibitory and antimicrobial activities of 3,4'-dihydroxy-alpha,beta-diethylstilbene, the isomer of diethylstilbestrol.

3,4'-Dihydroxy-alpha,beta-diethylstilbene (I), like diethylstilbestrol (II), showed phytogrowth-inhibitory and antimicrobial activities. First, compound I showed strong growth-inhibitory activity against the roots of two kinds of plants. The inhibitory activity of I was almost equal to that of sodium 2,4-dichlorophenoxyacetate used as a positive control. The phytogrowth-inhibitory activity of I was much higher than that of II. Next, unlike II, I had broad antifungal spectrum against phathogenic fungi. Compound I showed antifungal activity against six kinds of Fusarium oxysporum sp. This compound also had antibacterial activity against pathogenic and plant-pathogenic bacteria. These antibacterial activities of I were as high as those of II, the isomer of I. It should be emphasized that by shifting one of the phenolic hydroxyl groups of II to meta-position, phytogrowth-inhibitory activity was largely increased, while antimicrobial activity was unchanged.