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Abstract
The present study is focusing on the chemical constituents of mango leaves that could implicate in the resistance of local Egyptian mango (Mangifera indica) cultivar called Alphonso to scale insect infestation. For comparison, the same chemical and biological investigation steps were also conducted on the highly susceptible mango cultivar (Sultani) in addition to three other susceptible mango cultivars (Zebda, Baladi, and Hindi). The Acuminata scale insect, Kilifia acuminata (Signoret) nymphs were used as a bio-indicator. Leaf components were extracted with solvents with different polarities, and fractionated using several column chromatographies, preparative TLC and preparative HPLC. Finally, the isolated bioactive compounds were characterized and quantified with various spectroscopic method including GC-MS, 1H-NMR, 13C-NMR, IR, and UV. Six bioactive compounds were isolated from hexane extract of Sultani leaves and were found to be highly attractant to K. acuminata and one compound was isolated from methanol extract of Alphonso leaves and was found to be toxic against K. acuminata. The repellant compounds isplated from Alphonso leaves were identified as ?-pinene, ?-pinene and limonene. The attractant compounds extracted from Sultani leaves were identified as cis-ocimene andtrans-ocimene while the toxic compounds isolatedfrom Alphonso leaves wasidentified as pyrogallo. The later compound has not been previously reported as a constituent of M.indica species. The overall results of this study suggest that the combined action of three repellant secondary metabolites, namely: ?-pinene, ?-pinene and limonene and one toxic compound, namely pyrogallol play an important role in resistance of Alphonso mango cultivar against scale insectpests in general or at least against K. acuminata scale insect.