Insecticidal Activity of Crude and Purified Preparations from Oleander (Nerium oleander L.) against Cotton Leaf-hoppers (Jacobisca lypica L.) Pest

Abstract

Natural products from plants, because of their diversified chemical nature, continue to be a source of several chemicals products useful as drugs and pesticides either in their own right or as lead compounds for synthetic of more effective products. The aim of this study was concerned with evaluation of efficiency of extract and purified fractions prepared from the toxic plant Nerium oleander, L. (Apocyanaceae) in the control of the serious agricultural insect pest Jacobysca lybica (Jassid). Ethanol was used as solvent in two methods (Cold and Hot). Three accessions distinguished by flower color were tested. Morphological parts of the most insecticidally active accession (red-flowered Nerium) was further divided into leaf, stem, flower, seed and root. The leaf was selected for further studies which included evaluation of insecticidal activity of crude extracts and fractions separated by TLC. Partial identification of the insecticidal active ingredient was performed using FTIR spectroscopy. The Hot extraction method gave better recovery of insecticidal activity compared with the Cold method. Storage of cured extracts of the leaves of red-flower Nerium at 4C° (refrigerator) for 45 days was better than room temperature. Of seven compounds separated from red-Nerium crude leaf extracts by TLC, three were active against Jassid. The three were shown by FTIR spectroscopy to be cardiac glycosides. The most active of the three contained a carboxylic acid moiety which may well be the cardenolide getatoxingenin. Synergism among the three most active compounds against Jassid was studied. Recommendation included further studies deal with the extract nature of insecticidally active cardenolides as glycosides or a glycones.