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

AbstractPyrethrum oleoresin has been distilled in an industrial 12‐in. wiped‐wall, falling‐film, short‐path still in order to 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.Substantially pure ‘Pyrethrin I’ and ‘Pyrethrin II’ have been obtained by fractionation of pyrethrum extract in a similar 2‐in. still. It was found that ‘Pyrethrin II’ has 3′2–4.0 times the knockdown activity of ‘Pyrethrin I’ against M. domestica; when synergised 5: 1 with piperonyl butoxide, however, ‘Pyrethrin II’ has only 1–9 times the knockdown activity of similarly synergised ‘Pyrethrin I’ against M. domestica. ‘Pyrethrin II’ has 0–95, 0–55 and 0–74 times the lethal activity of ‘Pyrethrin I’ against M. domestica, T. castaneum and C. oryzae respectively.