(±)-Involucrasin D, a pair of enantiomeric bisflavonoid from the roots of Shuteria involucrata and its anti-inflammatory activity

An undescribed bisflavonoid, named involucrasin D (1), along with two known flavonoids, 2(S)7,3',5'-trihydroxydihydroflavone (2) and sigmone (3) were isolated from the roots of Shuteria involucrata. A further chiral separation of 1 to yielded a pair of enantiomers (+)-1 and (-)-1. The structures were elucidated based on spectroscopic analyses and electron circular dichroism (ECD) calculations. Among them, bisflavonoid 1 and its enantiomers displayed remarkable anti-inflammatory effects by inhibiting the production of TNF-α and IL-6 in a dose-dependent manner.