Screening of 17 Chinese medicine plants against phytopathogenic fungi and active component in Syzygium aromaticum

Using the mycelia growth rate method, inhibition effects of ethanol extracts from 17 Chinese medicine plants were determinated against 8 species of plant pathogenic fungi, including Rhizoctonia cerealis , Fusarium graminearum , Gaeumannomyces graminis , Fusarium oxysporum f. sp. vasinfectum , Valsa mali , Colletotrichum gloeosporioides , Fusarium oxysporum sp. cucumebrium , Colletotrichum lagenarium . The results showed that the ethanol extracts of Syzygium aromaticum has the highest antifungal effect among 17 medicine plants on any tested pathogen, with inhibition rate above 60%, and the inhibition effects on V. mali and F. graminearum were the best, with inhibitory rate 96.3% and 97.4%, respectively. Then, the active substances in S. aromaticum were traced using indicator fungi V. mali and F. graminearum , and 2-methoxy-4-(2-propenyl) phenol (eugenol) was isolated by liquid–liquid extraction and silica gel column chromatography and inferred by 1 H-NMR and 13 C-NMR analysis. The EC 50 values of eugenol were 42.04 mg/L against V. mali and 190.58 mg/L against F. graminearum , showing excellent antifungi activity.