Chemical constituents from Polygonum capitatum Buch-Ham. ex D. Don

• Thirty-one known compounds were obtained from Polygonum capitatum.
• Five known compounds were obtained from the family of Polygonaceae for the first time.
• This study adds the chemotaxonomic data of P. capitatum.

This work describes the isolation and characterization of thirty-one compounds from Polygonum capitatum Buch-Ham. ex D. Don, including two triterpenes (1–2), ten flavonoids (7–16), nine lignans (17–25), nine phenolic compounds (4–7, 26–31) and one anthraquinones (3). Their structures were elucidated on the basis of various spectroscopic methods (UV, IV and NMR, including 2D experiments). It was the first report of compounds 13, 15, 17, 24, 25, 28, 29, 30, 31 from the genus Ploygonum, and the first report of compounds 13, 15, 17, 24, 25 from the family Polygonaceae.