Molecular evidence for natural hybridization between Ligularia nelumbifolia and Cremanthodium stenoglossum (Asteraceae, Senecioneae)

Natural hybridization occurred frequently in the sunflower family. To date, however, no study on natural hybridization involving in Ligularia and Cremanthodium has been reported. Here, we presented the molecular evidence for natural hybridization between Ligularia nelumbifolia (Bureau & Franch.) Hand.-Mazz. and Cremanthodium stenoglossum Ling & S.W.Liu. Four nuclear DNA regions were sequenced to test the natural hybridization hypothesis, and three chloroplast DNA regions were sequenced to determine the direction of hybridization. Analyses of the investigated DNA data suggested that all of the putative hybrid individuals were derived from hybridization between L. nelumbifolia and C. stenoglossum and that bidirectional hybridization occurred. Moreover, sympatric Ligularia tsangchanensis (Franch.) Hand.-Mazz. and Ligularia virgaurea (Maxim.) Mattf. ex Rehder & Kobuski were not apparently involved in the hybridization. Although NewHybrids analysis showed that all the putative hybrid individuals were F1 class, a low frequency of backcrossing to C. stenoglossum might exist in the hybrid swarm. In such a case, hybrids might serve as a bridge facilitating gene flow between L. nelumbifolia and C. stenoglossum, and hybrid speciation is unlikely to happen for these hybrid individuals without asexual reproduction. Given the poorly resolved phylogenetic relationship between Ligularia and Cremanthodium, the occurrence of natural hybridization between L. nelumbifolia and C. stenoglossum might provide new insights into the recircumscription and redelimitation of these two genera.

Eremophilane Sesquiterpenoids and Nor- and Dinorsesquiterpenoids from Ligularia virgaurea Collected in China

Four samples of Ligularia virgaurea collected in China afforded three new eremophilane sesquiterpenoids, one new norsesquiterpenoid, and two new dinorsesquiterpenoids as well as 28 known compounds. All the four samples belonged to the ligularol type (L type), one of the five chemotypes we have described for this species. The configuration of the previously reported eremophila-7(11),9-dien-12,8-olide is revised to be H-8α. The absolute configuration of ethyl 8-oxoeremophila-7(11),9-dien-12-oate was established to be 4 S,5 R by a DFT calculation.

Eremophilane-type Sesquiterpenes from the Leaves of Ligularia Virgaurea

A phytochemical study of the ethanolic extract of the leaves of Ligularia virgaurea led to the isolation of a new eremophilane-type sesquiterpene lactone, (4 S,5 R,6 S,8 S,10 R)–6β-angeloyloxy-eremophil-7(11)-en-10βH-8α,12-olide (1), along with a known eremophilane-type sesquiterpene, (4 S,5 R,6 S,10 S)–6β-angeloyloxy-10βH-furanoeremophil-9-one (2). Their structures were elucidated by extensive spectroscopic methods, including 1D and 2D nuclear magnetic resonance and high-resolution electrospray ionization mass spectrometry experiments, and the absolute configurations were confirmed by single-crystal X-ray diffraction analysis using the anomalous scattering of Cu Kα radiation.