A new antibacterial compound from Luo Han Kuo fruit extract (Siraitia grosvenori)

Luo Han Kuo fruit (Siraitia grosvenori Swingle) has been used in China for centuries as a sweetening agent, and also used to treat sore throat and cough. In our recent study, a new bioactive compound, (2R,3S,4S)-2,3-trans-3,4-cis-5,3'-bimethoxy-7-(trans-2-propenal)-3,4-flavandiol (1), named siraitiflavandiol was obtained. The structure has been determined on the basis of spectroscopic studies including 1D and 2D NMR ((1)H, (13)C NMR, (1)H-(1)H COSY, HSQC, HMBC, and NOESY), CD, EI-MS, and HR-EI-MS spectra. The new compound was evaluated in vitro for its inhibitory ability against the growth of oral bacterial species Streptococcus mutans, Porphyromonas gingivalis, and yeast Candida albicans. The minimum inhibitory concentrations were 6, 24, and 6 microg/ml, respectively.