S-Dihydrodaidzein is the (S)-enantiomer of dihydrodaidzein which is one of the most prominent dietary phytoestrogens[1][2].
[1]. Shimada Y, et al. Identification of a novel dihydrodaidzein racemase essential for biosynthesis of equol from daidzein in Lactococcus sp. strain 20-92. Appl Environ Microbiol. 2012 Jul;78(14):4902-7. [2]. Franke AA, et al. Liquid chromatographic-photodiode array mass spectrometric analysis of dietary phytoestrogens from human urine and blood. J Chromatogr B Analyt Technol Biomed Life Sci. 2002 Sep 25;777(1-2):45-59.