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The chemical constituents of the root extracts and the evolutionarily neutral DNA base sequences were studied for 28 samples of Ligularia duciformis, L. kongkalingensis, and L. nelumbifolia collected in Sichuan and Yunnan Provinces of China. The samples could be classified into four chemotypes (1-4). Sesquiterpenoids having eremophilane and oplopane skeletons were isolated from two (Chemotype 1) and three (Chemotype 2) samples, respectively. Two new oplopane derivatives were isolated and their structures were determined. In 18 samples, phenylpropenoids were the major components (Chemotype 3). In five samples, neither phenylpropenoids nor sesquiterpenoids were found (Chemotype 4). Despite this large chemical variety, no correlation was found between the chemotype and the morphological criteria of species identification. The analysis of the evolutionarily neutral DNA regions also indicated that the samples were not separated into distinct clades and that introgression was extensive.

Chemical constituents of Ligularia hookeri (Asteraceae) collected in Yunnan and Sichuan Provinces in China were examined for the first time. Seven furanoeremophilanes, five of which were new, as well as known bisabolane-and eudesmane-type sesquiterpenoids, were isolated. Spectroscopic evidence indicates that the previously reported 3β-(2′-methylpropenoyloxy)furanoeremophilan-15,6β-olide should be revised to 3β-(2′-methylpropenoyloxy)furanoeremophilan-15,6α-olide.Key words Ligularia hookeri; Asteraceae; eremophilane; sesquiterpene; structure elucidation; internal transcribed spacerWe have been analyzing both the chemical composition and the DNA sequence of evolutionarily neutral regions of Liguralia (Asteraceae) plants, mainly from Sichuan and Yunnan Provinces in China, in order to study the mechanism of diversification of secondary metabolites.1,2) Intra-specific diversity has been revealed in most of the Ligularia species hitherto studied and found to be high in some species. The results of DNA analysis have suggested that the diversity in the chemicals has genetic origins in most cases. Furanoeremophilanes and/or eremophilan-8-ones have been isolated from most of the major Ligularia species; in particular, furanoeremophilanes are found more often than eremophilan-8-ones. In addition, most of the species that produce furanoeremophilanes appear to be more abundant than those that do not. These observations have led us to propose a hypothesis that furanoeremophilane-producing species or intra-specific populations are ecologically advantageous over eremophilan-8-one-producing ones.

The chemical constituents of the root of Ligularia duciformis, collected in Yunnan Province of China, was studied and two new oplopane-type sesquiterpenoids were isolated, whose structures were determined on the basis of spectroscopic evidence. Quite recently, oplopane-type compounds were found in Ligularia narynensis, and this is the second example to isolate oplopane-type sesquiterpenoids from Ligularia plants.