Search

Ligularia cymbulifera is one of the predominant species in the Hengduan Mountains, China, and has led to a decrease in the amount of forage grass in this area. However, little is known about the mechanism behind its predominance. In this study, two novel eremophilane sesquiterpenes, ligulacymirin A and B (1 and 2), together with seven other known terpenoids (3–9), were isolated from the roots of L. cymbulifera. The structures of 1 and 2 were determined by spectroscopic methods and single-crystal X-ray diffraction. Each compound showed phytotoxic activities against Arabidopsis thaliana, and each was detected and identified in rhizosphere soil by UHPLC-MS. Compound 3 was the most potent phytotoxin, showing remarkable inhibition against both seedling growth (EC50 = 30.33 ± 0.94 μg/mL) and seed germination (EC50 = 155.13 ± 0.52 μg/mL), with an average content in rhizosphere soil of 3.44 μg/g. These results indicate that terpenoids in L. cymbulifera roots might be released as phytotoxins in rhizosphere soil to interfere with neighboring plants.

Ligularia cymbulifera is one of the predominant species in the Hengduan Mountains, China, and has led to a decrease in the amount of forage grass in this area. However, little is known about the mechanism behind its predominance. In this study, two novel eremophilane sesquiterpenes, ligulacymirin A and B (1 and 2), together with seven other known terpenoids (3–9), were isolated from the roots of L. cymbulifera. The structures of 1 and 2 were determined by spectroscopic methods and single-crystal X-ray diffraction. Each compound showed phytotoxic activities against Arabidopsis thaliana, and each was detected and identified in rhizosphere soil by UHPLC-MS. Compound 3 was the most potent phytotoxin, showing remarkable inhibition against both seedling growth (EC50 = 30.33 ± 0.94 μg/mL) and seed germination (EC50 = 155.13 ± 0.52 μg/mL), with an average content in rhizosphere soil of 3.44 μg/g. These results indicate that terpenoids in L. cymbulifera roots might be released as phytotoxins in rhizosphere soil to interfere with neighboring plants.

Three Ligularia species (L. tongolensis, L. cymbulifera, and L. atroviolacea) were examined with respect to the chemical composition and nucleotide sequence. Furanoeremophilanes were found to be produced in the root of all samples of the three species collected in northwest Yunnan and southwest Sichuan. Eight furanoeremophilanes were identified, two of which were new. Most of the identified furanoeremophilanes were oxygenated at 3, 6, and 15-positions. The nucleotide sequence of the atpB-rbcL intergenic region was found to be essentially the same in the three species. These similarities imply that the three Ligularia species, all belonging to the section Corymbosae, are close to one another. The intra-specific diversity in the two widely distributed species in the Hengduan Mountains area, L. tongolensis and L. cymbulifera, were in contrast. Four out of 19 L. tongolensis samples contained a strongly Ehrlich-positive compound besides a number of positive compounds, and five variants of the atpB-rbcL sequence were found in these samples. In contrast, no variation was observed in 13 L. cymbulifera samples with respect to the furanoeremophilane composition or the atpB-rbcL sequence. The lack of diversity in L. cymbulifera probably resulted from the uniformity of its habitat.

From the roots of Ligularia cymbulifera collected in Yunnan Province, China, two new eremophilane-type sesquiterpenoids (1 and 2) together with ten known compounds (3–12) were obtained through the precise chemical component elucidation. The structure determination was mainly carried out with 1D and 2D NMR data.

Four new highly oxygenated bisabolane sesquiterpenoids (1–4) were obtained from the EtOH extract from Ligularia cymbulifera, and their structures were elucidated by interpretation of spectroscopic data. Their relative configurations were clarified by a detailed analysis of 1H NMR coupling constants, nuclear overhauser effect (NOE) experiments and two-dimensional NMR spectra. These four new compounds were assayed for their antimicrobial activities against four Gram-positive and Gram-negative bacteria, as well as against one human pathogenic fungus.