Comparative extraction and enrichment techniques for pyrethrins from flowers of Chrysanthemum cinerariaefolium

This paper reports comparative extraction efficiencies and enrichment methods for natural insecticidal compounds pyrethrins from the dried flowers of Chrysanthemum cinerariaefolium using different techniques and solvent systems. Four different extraction techniques viz. percolation, agitation with heat, sonication and soxhlet using five different solvent systems hexane, ethyl acetate, acetone, acetonitrile and methanol were evaluated. In these studies, it was observed that maximum extract yield was obtained using methanol as extracting solvent by soxhlet technique, although the content of total pyrethrins was higher in the hexane extract than in methanol. The successive and maximum enrichment of the total pyrethrins was achieved by solid-matrix partitioning of the extract using acetonitrile as extracting solvent followed by treatment with activated charcoal, subsequent chilling and filtration by which enrichment of total pyrethrins up to 60.37% content was obtained. The quantitative analysis of the extraction and enrichment development protocol was validated by a simple, accurate, reproducible RP-HPLC-UV method using a binary gradient elution comprising of acetonitrile and water. The separation was achieved on a Waters-symmetry C18 column (150 mm × 3.9 mm i.d., 5 μm) that achieved a greater degree of linearity within an overall concentration range of 5-500 μg mL−1 and higher degree of correlation (0.9842 ≤ r2 ≤ 0.9987) for all the pyrethrin esters.