Isolation of Ethyl <i>p</i>-Methoxycinnamate from <i>Azadirachta indica</i> Root Bark as Hong Kong Caterpillar (<i>Tenebrio molitor</i>) Antifeedant

Abstract

This study aims to identify the antifeedant activity of Azadirachta indica A. Juss root bark against Hong Kong caterpillar (Tenebrio molitor). A. indica A. root was macerated in n-hexane, ethyl acetate, and methanol. The investigation of antifeedant activity was conducted by using the no choice leaf disk method. The antifeedant activity (%AI) tests showed that the extracts of n-hexane, ethyl acetate, and methanol with each concentration of 0.5% were 6.71, 71.78, and 40.14%, respectively. The ethyl acetate extract demonstrated the most active antifeedant activity. Ethyl acetate extract was fractionated to obtain five subfractions (A-E). Each subfraction with each concentration of 0.5% showed the %AI of 70.55, 85.29; 67.40, 82.70 and 82.22%, respectively. Furthermore, GC-MS results demonstrated that ethyl acetate extract contained 19 compounds. The main compounds are methyl hexadecanoate and methyl 8-octadecenoate. Further purification of fraction A, which has the highest amount, was then carried out. The obtained isolate, i.e., A32, was determined as ethyl p-methoxycinnamate confirmed by 13C- and 1H-NMR, FTIR, and MS spectra. The presence of ethyl p-methoxycinnamate makes A. indica A. root is potential as T. molitor antifeedant. The implication of these findings is to reference herbal antifeedants and reduce the use of synthetic pesticides.

Keywords

• azadirachta indica a. juss root bark, antifeedant, ethyl p-methoxycinnamate, tenebrio molitor.