Distillation of pyrethrum extract in a wiped‐wall, falling‐film, short‐path still: Separation of ‘pyrethrin I’ and ‘pyrethrin ii’ and determination of their relative biological activities

Abstract

Pyrethrum oleoresin has been distilled in an industrial Iz-in. wiped-wall, falling-film, short-path still in order t o produce a decolorised dewaxed pyrethrum extract. The distilled material was free from isopyrethrins and a series of bio-assays showed the biological activities of the distilled and undistilled extracts to be identical.Pyrethrin I ' and ' Pyrethrin I1 ' have been obtained by fractionation of pyrethrum extract in a similar z-in. still. It was found that ' Pyrethrin 11 ' has 3'2-4'0 times the knockdown activity of ' Pyrethrin I ' against M . domestica ; when synergised 5 : I with piperonyl butoxide, however, ' Pyrethrin I1 ' has only 1.9 times the knockdown activity of similarly synergised ' Pyrethrin I ' against M . domestica. Pyrethrin I1 ' has 0.95,0*55 and 0.74 times the lethal activity of ' Pyrethrin I ' against M . domestics, T. castaneum and C . oryzae respectively.Substantially pure