Chemosystematic implications of flavonoids of the Ostericum sieboldii complex in East Asia

The chemosystematic relationships among East Asian Ostericum species were investigated through flavonoid analysis and morphometric studies. Two distinct chemotypes were identified in O. sieboldii populations: a flavonol type, containing primarily kaempferol and quercetin glycosides, found in Japan and eastern China, and a flavone type, characterized by apigenin and luteolin glycosides, prevalent in Korea and northern China. Morphometric analysis of 311 specimens using 18 quantitative characters revealed that while O. grosseserratum could be distinguished from O. sieboldii , the two O. sieboldii chemotypes showed no significant morphological differentiation except for minor variations in inflorescence size and leaf pubescence. The flavonoid patterns suggest that the Korean flavone-type populations represent a derived form that evolved from the primitive flavonol-containing populations in eastern China and Japan. This chemical variation is accompanied by cytological diversity across the genus, ranging from the unique chromosome number in O. grosseserratum (2n = 18) to the polyploid condition in O. maximowiczii (2n = 44). These findings provide new insights into the chemical diversity and cytological variation of Ostericum in East Asia, which clarify regional differentiation within O. sieboldii and highlight patterns of chemical divergence among related species.