Screening Effective Antifungal Substances from the Bark and Leaves of by the Bioactivity-Guided Isolation Method.

To find good antifungal substances by the bioactivity-guided isolation method, we tracked down the effective antifungal substances in the bark and leaves of , and isolated three antifungal compounds , , and The structures were identified as xanthyletin, luvangetin, and avicennin by H-NMR, C-NMR, and HRMS spectra. Particularly, compound had several isomers, and the H-NMR spectra of in different solvents showed a significant difference. To determine the stereo structure of 2, a single crystal was prepared and identified by X-ray diffraction as Luvangetin. Moreover, the difference of H-NMR data of between in solvent dimethyl sulfoxide-d (DMSO-d) and deuterated chloroform (CDCl), and other reported isomers were discussed for the first time. The bioassay results indicated that the three compounds , , and displayed low to high antifungal activities against tested phytopathogenic fungi. In particular, all compounds , , and showed excellent antifungal activities against Pyricularia oryzae and , with the values of half maximal effective concentration (EC) ranging from 31 to 61 mg/L, and compound was also identified as a more potent inhibitor against Fusaium graminearum (EC = 43.26 ± 1.76 mg/L) compared with fungicide PCA (phenazine-1-carboxylic acid) (EC = 52.34 ± 1.53 mg/L). The results revealed that compounds and were the main antifungal substances of Z. avicennae, and can be used as lead compounds of a fungicide, which has good development value and prospect.