Prenylated Flavonoids from the Stems and Leaves of Desmodium caudatum and Evaluation of Their Inhibitory Activity against the Film-Forming Growth of Zygosaccharomyces rouxii F51

In order to provide scientific evidence for the relationship between the traditional usage, stems and leaves of Desmodium caudatum being used for protecting miso from spoilage, and its Japanese name (miso-naoshi), phytochemical study on the stems and leaves of this plant was carried out. Seven new prenylated flavonoids (1-3, 15-18), together with 19 known compounds (4-14, 19-26), were isolated, and the structures of new compounds were elucidated by extensive spectroscopic analyses. The minimum inhibitory concentrations (MICs) of 28 flavonoids, including 17 compounds (1, 2, 4, 5, 7-14, 20-22, 24, 25) isolated in this study and 11 flavonoids (27-37) previously isolated from the roots of this plant, against the film-forming yeast of Zygosaccharomyces rouxii F51 were determined. Fifteen compounds (2, 4, 5, 11, 12, 14, 21, 22, 25, 27, 28, 32-35) inhibited the film-forming growth of Z. rouxii F51 (MIC values, 7.8-62.5 μg/mL), among which 2",2"-dimethylpyran-(5",6":7,8)-5,2'-dihydroxy-4'-methoxy-(2R,3R)-dihydroflavonol (11) demonstrated potent inhibitory activity with an MIC value of 7.8 μg/mL.