Chemistry of sesquiterpenoids from Inula racemosa and their evaluation as pesticides
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
The dissertation incorporates the isolation of sesquiterpene lactones- alantolactone and isoalantolactone from root extract of Inula racemosa using extensive column chromatography over silver nitrate impregnated silica gel. Reduction of these isolated compounds was carried out using sodium borohydride, lithium tri-tert-butoxyaluminohydride and magnesium in methanol. Dibromocyclopropane derivatives were prepared using bromoform/potassium hydroxide in presence of phase transfer catalyst. Allylic oxidation of isoalantolactone was carried out selenium dioxide and tert-butyl hydroperoxide. Decomposition of pyrazoline derivatives of sesquiterpene lactones under heat, microwave and ultraviolet radiations (in presence or absence of sensitizer) were carried out. I. racemosa root extract was partitioned into its non-polar and polar fractions and were subjected to various biological activities using different methods such as mortality, repellency and antifeedant assay for insecticidal activity against Tribolium castaneum; egg hatch inhibition and juvenile mortality test for nematicidal activity against Meloidogyne incognita and spore germination inhibition for fungicidal activity against three fungi i.e. Alternaria triticina, Drechslera oryzae and Fusarium moniliforme. Non-polar fraction was most effective in all bioassays except in egg hatch inhibition studies where root extract was most effective. Isolated compounds and their derivatives showed antifungal potential against three test fungi. Isoalantolactone derivatives were more effective in comparison to alantolactone. Based on antifungal activity structure activity relationship was derived.
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