Identification of new flavonol O-glycosides from indigo (Polygonum tinctorium Lour) leaves and their inhibitory activity against 3-hydroxy-3-methylglutaryl-CoA reductase

• Comprehensive analysis of flavonoids from indigo leaves were performed.
• We separated and identified 11 peaks of flavonoid species by UPLC–ESI-TOF/MSE.
• The predominant species were elucidated as new flavonol O-glycosides.
• These flavonol O-glycosides are effective to inhibit HMG CoA-reductase in vitro.
• The compounds may be useful sources to control cholesterol biosynthesis.

Indigo plant (Polygonum tinctorium Lour) has been utilized as a medicinal plant with a variety of biological activities. We have recently detected higher levels of flavonoids in indigo leaves. This study was undertaken to conduct the simultaneous analysis of those flavonoids using total extracts from indigo leaves by ultra-performance liquid chromatography–electrospray ionization-time-of-flight/mass spectrometryE (UPLC–ESI-TOF/MSE). The analysis by UPLC–ESI-TOF/MSE allowed us to determine 11 peaks of flavonoid species. The chemical structures of these compounds were identified as flavonol O-glycosides with different types of aglycones by the combination of spectroscopic and chemical methods. The predominant compounds were flavonol O-glycosides with 3,5,4′-trihydroxy-6,7-methylenedioxyflavone as an aglycone. Of these, three compounds were elucidated as new compounds. All the isolated flavonol O-glycosides exhibited the inhibitory activity against 3-hydroxy-3-methylglutaryl-CoA reductase in a dose-dependent manner with different potencies. Taken together, our results suggest the potential usefulness of the major flavonol O-glycosides from indigo leaves in controlling cholesterol biosynthesis.

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