Abstract: An anthraquinone, 1, 6, 8 – trihydroxy – 3 – methylanthraquinone (emodin) with pesticidal activity has been isolated from the leaves of Cassia alata. The powdered leaves were extracted successively with pet ether (40-60) and ethanol in a soxhlet extractor. Bioassay using the brine shrimp lethality test as well as pesticidal activities against Sitophilus zeamais and Callosobruchus maculatus were evaluated.  Column chromatography and diagnostic thin layer chromatography were employed to fractionate the organic compounds present in the leaves. Gradient elution was done using diethyl ether-pet ether (1:1 v/v); hexane-chloroform (3:2 v/v); pet ether-ethanol (3:4 v/v) and hexane-acetone (3:1 v/v). The eluents were collected as 5ml fractions into labeled test tubes. All fractions containing homogenous materials were pooled and concentrated using Buchi-rotary evaporator R144, to give the purified products. Filter paper test was performed to establish the pesticidal activity of the isolated compounds by estimating the LC50 values within 24 hours. The structural elucidation of the pesticidal compound was achieved by chemical and spectroscopic methods. The pesticidal activity of Cassia alata was compared with the popular natural insecticide neem and a commonly used insecticide Actellic Super EC.

Keywords: Bioactivity-directed, Pesticidal, Chromatography, Stored insects, Infrared Spectra, Cassia alata