Bioactivity of plant extracts against two stored product insects and use of chromatography and infrared analyses for defining the toxic compounds

Abo Arab, R.B.; G.M.M. Zayed and Abeer, A. Salm

Abstract

Among five tested plant extracts namely, Ammi majos, artemesia herba alba, Chenopodium murale, Eugenia aromatica and Pimpinella anisum, two species proved great activity against the experimental pests Callosobruchus maculatus (F.) and Sitophilus oryzae (L.). These two plant species were Pimpinella anisum and Eugenia aromatica. Extraction was carried out by using N-hexane and methanol. Synthetic chemical insecticide, pirimiphos-methyl was used as a standard reference against stored product insects. Pirimiphos methyl showed the highest toxicity and percent reduction of progeny for the two tested insect species. Also, Pimpinella anisum and Eugenia aromatica achieved high detrimental effect on offspring of the two tested insects. Results obtained exhibited some different effects between the two selected plant extracts on the tested insects. Therefore, chemical analyses for the composition of the two selected extracts were achieved by Thin Layer Chromatography (T.L.C.) and infrared spectra. Phytochemical constituents differed according to the solvent used and the plant species. Sterols, triterpenes, carbohydrates, and glycosides were found in high amount of ethanol extracts of E. aromatica and P. anisum. Tannins, ferric chlorides and flavonoids were found in trace amount of n-hexane extracts of E. aromatica and P. anisum. It could be concluded that, sterols and triterpenes, saponins, alkaloids, and glycosides are responsible for bioactivity of the studied plants. T.L.C. analysis revealed the occurrence of two fractions of P. ansimum of n-hexane and five fractions of ethanol, for the same plant, four fractions of E. aromatica with ethanol and three of n-hexane extracts. Results of infrared spectroscopy explain 14 curves with different peaks carrying special wavelength indicating the active phytochemical groups in each curve.

Key words

Ammi majos , artemesia herba alba , Chenopodium murale , Eugenia aromatic, Chromatography (T.L.C.)