Loss of Pyrethrins Content during Drying of Chrysanthemum cinerariifolium Flowers in Direct Sunlight

H. O. Otieno; David K. Kariuki; John M. Wanjohi

H. O. Otieno Department of Chemistry, University of Nairobi
David K. Kariuki Department of Chemistry, University of Nairobi
John M. Wanjohi Department of Chemistry, University of Nairobi

Keywords: Chrysanthemum, cinerariifolium, Pyrethrins, Drying, Darkness, Sunlight, UV

Abstract

Pyrethrins are organic compounds derived from the flowers of Chrysanthemum cinerariifolium for their insecticidal activities. Pyrethrins I and Pyrethrins II are the two main classes in which Pyrethrins are grouped. The two groups are composed of six organic compounds namely pyrethrin I, jasmolin I, cinerin I, pyrethrin II, jasmolin II and cinerin II. The compounds are degradable on exposure to direct sunlight, moisture and temperatures. Pyrethrins are used as a broad spectrum natural insecticide in agriculture and public health. The aim of this research was to establish the differential total extractable pyrethrins content on drying flowers in direct sunlight and in darkness. Mature pyrethrum flowers from experimental farm, College of Agriculture and Veterinary Sciences, Kabete campus, University of Nairobi, were harvested in brown paper bags, divided into four sets and taken to the laboratory. The first set of flowers were dried in direct sunlight for two weeks and the second set to a constant weight at a temperature of between 16-29OC. The third set were dried in darkness for two weeks and the fourth set to a constant weight at room temperature. Drying was done between 3rd- 17th of August 2019. The dried flowers were then ground into fine powder and extracted using Soxhlet extraction method with hexane. The extracts were refined and analyzed by titrimetric method. Pyrethrum flowers were found to achieve maximum moisture loss at varying times depending with the dying method used. The yield of pyrethrins obtained on drying the flowers to constant weight in direct sunlight was 1.02% while in darkness was 1.38%. The percentage of pyrethrins obtained from flowers dried in direct sunlight for two weeks was 0.86 and 1.01 in darkness. Moisture level for the flowers dried to a constant weight was 9%. The pyrethrins I:II ratio was found to vary for the two drying methods used. The best condition to dry the pyrethrum flowers was found to be in darkness to a moisture content of 9%.