A new Diels-Alder type adduct and two new flavones from the stem bark of Morus yunanensis Koidz

Fractionation of the ethanolic extract of the stem bark of Morus yunanensis resulted in the isolation of a new Diels - Alder type adduct and two new flavones, named yunanensin A (1), yunanensol A (2) and yunanensol B (3), respectively, together with a known flavone (4). Their structures were determined on the basis of spectroscopic analysis and chemical methods. Among them, compound 1 showed moderate antioxidant and significant cytotoxic activities, and compound 2 showed potent anti-inflammatory activity.