Identification of 6,7-dimethoxychromone as a potent allelochemical from jatropha podagrica

Jatropha podagrica Hook. is cultivated as an ornamental plant and is also used in traditional medicine. The species has various pharmacological properties, but it has not yet been investigated for any potential allelopathic activity and allelopathic substances. In this study, an allelopathic active substance was isolated from an aqueous methanol extract of J. podagrica leaves through chromatography and reverse-phase HPLC. The substance was characterized as 6,7- dimethoxychromone by spectral analysis. 6,7-Dimethoxychromone significantly inhibited the shoots and roots of cress at concentrations greater than 0.3 mM. The concentrations required of 6,7-dimethoxychromone for 50% growth inhibition of cress shoots and roots were 0.95 and 0.83 mM, respectively. The inhibitory activity against the seedling growth of cress indicates that 6,7-dimethoxychromone may contribute to the allelopathic effects and may be responsible for the allelopathic activity in J. podagrica. This report is the first on the allelopathic activity of 6,7-dimethoxychromone as an allelopathic substance from J. podagrica.