Antimicrobial Activities of Nerium indicum Mill Extracts on Fungal Pathogens

The branches and leaves of Nerium indicum Mill plants were extracted using petroleum ether, ethyl acetate or nbutanol in this study. The antimicrobial activities of the extracts against 5 pathogenic fungi on plants (i.e., Gerlachia nivalis, Gaeumannomyces graminis, Venturia nashicola, Colletotrichum capsici, and Magnaporthe oryzae) were determined based on the fungal growth rates under the treatments. From the data, regression equations were obtained, and EC₅₀ calculated. It was found that the extracts exhibited varying inhibitory rates, which increased with increasing concentration of the extract. The ethyl acetate extract showed the greatest inhibitory effects on the pathogens. At a concentration of 10 mg·mL^-1, the extract demonstrated an inhibition rate exceeded 65.0% against all 5 fungi, especially G. nivalis, which reached 85.7% with an EC₅₀ of 2.04 mg·mL^-1. The petroleum ether extract and the nbutanol extract followed in that order on the inhibition effect. All 3 extracts retarded the growths of G. nivalis with an EC₅₀ below 6.28 mg·mL^-1, which was significantly lower than the EC₅₀ on other fungi tested.