Abstract: Abstract From the root of Paeonia suffruticosa and P. lactiflora seven compounds have been isolated. They are identified as paeoniflorin I, benzoylpaeoniflorin II, oxypaeoniflorin III, paeonol IV, paeonoside V, paeonolide VI and apiopaeonoside VII. The contents of the seven constituents in the root of 23 Paeonia taxa, including 19 species and 6 varieties, are determined by means of the quantitative HPTLC scanning method. The results show that paeoniflorin occurs ubiquitously in all the species examined and is the characteristic constituent of the family Paeoniaceae; The paeonol compounds (IV, V. VI, VII) are found to be restricted to the woody Sect. Moutan and notably absent in the herbaceous Sect. Paeon. This differentiation gives a support to the division of sections in Paeoniaceae. The chemical comparison between Paeoniaceae and 15 possibly related families shows that Paeoniaceae is different from Ranunculaceae, Ranunculales of Magnoliales and is similar to Dilleniaceae, Theaceae and Rosaceae in some respects. The chemical data support the suggestion that Paeoniaceae be elevated to the order rank, Paeoniales.

Key words: Paeoniaceae, Peony, Paeoniflorin, Paeonol, Chemosystematics