Bioassay guided isolation and structural elucidation of anti-feeding compounds against chilo partellus (swinhoe) in fruits elae odendron buchananii l.

Abstract

This thesis describes a feeding deterrent bioassay guided chromatographic isolation of compounds found in the fruits of Elaeodendron buchananii loes, a Kenyan folk medicinal plant that is used to cure diarrhoea, syphillis, wounds and stomachache, and their structural elucidation.

Unripe fruits of E. buchananii were extracted with methanol, n - hexane, and chloroform successively. Feeding bioassay of the three extracts on their instar larvae of the stem borer Chilo partellus Swinhoe demonstrated that only the chloroform extract was active 51.6% deterrence at 100 g/disc . The chloroform extract was then chromatographed on silica gel using gradient elution of a mixture of acetone in petroleum ether Bp 40-60°C to give three active fractions, V, VI and VII that gave percentage anti-feeding activities of 88.5, 77.8 and 60.9 respectively at 100g/disc. Further chromatographic work on fraction V led to the isolation of 1, 2, 6-triacetoxy-9, 15-dibenzoyloxy--dihydroagarofuran (1), a new compound, and -sitosterol (2) at 100g/disc. Some functional groups present in it were determined.

The of (1) and (2) were determined by spectral data analysis and correlation with published data. The characteristic mass spectral fragmentation patterns and molecular ions, 13 Cnmr and 1Hnmr chemical shifts and their integration led to the formulations of the molecular structures. The functional groups were inferred from IR, UV and Distortionless Enhancement by Polarization Transfer (DEPT) spectra. Correlation Spectroscopy (COSY) spectra was useful in assigning the stereochemistry of the structures.