Neolignans and Sesquiterpenoid from Piper yunnanense

Two biphenyl-type neolignans with a rare dibenzofuran skeleton, including a new one piyunneolignan A (1) and a known one piperneolignan D (2), together with a new sesquiterpenoid piyunin A (3), were isolated from the leaves and twigs of Piper yunnanense. Their structures were established on the basis of comprehensive spectroscopic data analysis and electronic circular dichroism (ECD) calculation. Piyunneolignan A (1) featured a rare C-2-C-2'/C-3-O-C-3' linkage. Compounds 1-3 were evaluated for their antimicrobial and cytotoxic activities against a panel of bacteria, fungi, and human cancer cell lines, respectively.