The isolation and identification of the acaricidal principal extracted from Mentha piperita

Abstract

The objective of this study is to measure the toxicity of acaricidal of Mentha piperita extracts, and to isolate and identify the chemical compounds of the extracts. This experiment uses three kinds of solvents - petroleum ether, chloroform, and methanol in extraction with the. Liquid-liquid partition technique. The acaricidal substance was isolated and purified by silica gel column, chromatography, and thin layer chromatography (TLC) together with iodine chromo test; it is traced with the slide retting method. Finally the experiment employs UV photo spectrum, HPLC, RI, and MS, and other techniques in identifying the active substance. The study finds that part of the crude petroleum ether extract from the Mentha piperita land shows significant acaricidal effect to Tetranychus cinnabarinus-when its density reaches 1 mg/ml, lethal rate of mature mites is 87.05 % within 24 hours, and mites' eggs 93.16 %. According to Duncan's inspection, three kinds of solvents of crude extracts display great differences in the lethal rate of mature mites and mite eggs (P < 0.05). The study also finds that chloroform extract and methanol extract from the upper menthe lands has relatively weak acaricidal effect - their lethal rates to mature mites comes at 28.51% in 24 hours, and mites eggs 10.73 %. Based on a liquid-liquid extraction of petroleum ether by methanol, the crucial components of the acaricidal substance appear to exist in petroleum ether of lower polar whose lethal rate of mature mites reaches 93.75 % within 24 hours. The study gains eight fractions from the isolation of the petroleum ether extracts. With bioactive tracing, one of them provides a sample compound V which possesses higher acaricidal effect. Its lethal concentration (LC50) reaches 0.5464 mg/mL. Its credible interval is 0.3268 - 0.9134 mg/mL. The purity of the sample compound was 89.16 % based on HPLC. MS shows its molecular ion peak being 414 which reveals its sterol ring structure according to the corresponding data base. IR reflects that the substance shows notable characteristic peaks at 1160 cm-1, 1450 cm-1, 1380 cm-1 and 1700 cm-1. It is thus determined that the substance isolated from Mentha piperita in this study is a β-sitosterol. © 2012 Springer-Verlag GmbH.