Abstract:
Objective Ethanol extracts of 5 species of plants were analyzed for possible antibacterial and/or insecticidal applications in disease control.
Method Aconitum Pendulum, nutmeg (Myristica fragrans Houtt), Butea monosperma (Lan.) Kuntze, Pterocephalus hookeri, and Rhododendron molle were selected for the extraction. The inhibitory activities of the extracts against plant pathogenic fungi as well as the virulence to aphids and locusts were determined. Subsequently, the greatest locust-killing capacity demonstrated by the R. molle extract was subjected to a step-wise fractional extraction and column separations to isolate active substances.
Result The nutmeg extract applied at 1 000 mg·L-1 level inhibited the growth of Pythium aphanidermatum, Physalospora berengeriana and Rhizoctonia solani at 75.23%, 77.78% and 88.85%, respectively. The R. molle extract showed the lethality on aphids at a rate of 55.38% with the dosage of 2 000 mg·L-1 and 100% with 10 000 mg·L-1in 48h; while that on locusts, 44.83% in 24h and 86.96% in 96h with 10 000 mg·L-1. At 1 000 mg·L-1 dosage, the active fraction, Ⅲ-2-2, isolated from the extract rendered the lethal rates on locusts of 53.57% in 24h and 90.48% in 120h.
Conclusion The antibacterial activity of nutmeg extract was the highest among all extracts; the R. molle extract displayed the highest toxicity on aphids and locusts; most of the active substances in the extracts were petroleum ether and dichloromethane soluble; and, Ⅲ-2-2 obtained from the dichloromethane fraction had the highest potency toward locusts.