Biological activities of 3,3'-dihydroxy-alpha,beta-diethylstilbene and its isomer, diethylstilbestrol.

3, 3'-Dihydroxy-α, β-diethylstilbene (I) and its isomer, diethylstilbestrol (II), showed antifungal activity against plant-pathogenic fungi, phytogrowth-inhibitory activity and a hypotensive effect on rats. First, I exhibited rather strong antifungal activity against plant-pathogenic fungi; the minimal inhibitory concentrations against Fusarium oxysporum f. sp. lycopersici. Botryotinia fuckeliana and Pyrenophora graminea were 4 μg/ml. On the other hand, the activity of II was weaker than that of I. Secondly, both compounds inhibited the growth of roots of two plants species even at low concentration of 50 ppm. Thirdly, I and II showed a hypotensive effect on rats (I, -23.33 ± 5.03 mmHg; II, -41.00 ± 2.40 mmHg; 10 mg/kg, i.v.). Unlike II, I has virtually no hormonal activity. It is noteworthy that in spite of the loss of hormonal character in going from II to I, the abovementioned activities are fully retained.