Allelochemicals of and their effects on various plants and rhizosphere microorganisms.

(Araliaceae) is an important ginseng herb with various health benefits and a history of cultivation in southwestern China over 400 years. In recent years has faced serious continuous-cropping obstacles due to its large-scale cultivation. In this study, we aim to explore the allelochemicals of and their interactions with various plants and rhizosphere microorganisms. The chemical constituents of the soil cultivated with 3-year-old were studied by column chromatography, spectroscopic and GC-MS analyses. We identified 13 volatile components and isolated six triterpenes (-, -) and one anthraquinone (). Compounds - were tested for their effects on seed germination and root elongation in , corn, wheat, turnip, water spinach and . We also examined the effect of compounds - on the growth of ten rhizosphere microorganisms of . At a concentration of 1.0 μg mL, compounds and - caused the death of root cells and compounds , and induced the death of root cells of . Compounds - and inhibited elongation of root tip cells at a concentration of 10.0 μg mL. Moreover, at a concentration of 0.1 mg mL, compounds , , and inhibited the growth of probiotics and promoted the growth of pathogens of . These results suggest that these isolated ursane-type triterpenoid acids and anthraquinone are potential allelochemicals that contribute to continuous-cropping obstacles of .