| dc.description.abstract | Polygonum senegalense is one of the eleven Polygonum species
growing in Kenya highlands. P. senegalense finds use in ethno-medical mode
of therapy in this country along with other species of the Polygonaceae family.
In this work, the aerial parts of the plant were first washed with
acetone, then the dried powdered material was sequentially extracted with cold
70 % and 50 % aqueous methanol for two days each and the combined
aqueous extracts were partitioned into ethyl acetate. This was followed by
chromatragraphic (analytical, preparative t.l.c. and column) analysis of the
ethyl acetate fraction using silica gel, impregnated with 3 % oxalic acid
solution and Sephadex LH-20. Finally the isolates were characterised using
spectroscopic methods (IR, UV, NMR and MS).
The secondary metabolites isolated and characterised from the plant
material were 2',4' -dihydroxy-6' -methoxychalcone (1), kaempferol (4',5,7-
trihydroxyflavonol) (3), quercetin (3' ,4' ,5, 7-tetrahydroxyflavonol) CJ.),
quercetin-3-J3-0-galactoside (4), quercetin- 3-J3-0-g1ucoside (5), 2' -J3-0-gluco-
4' -hydroxy-6' -methoxydihydrochalcone'(ji) and quercetin-3-J3-0-glucoside-2"-
gallate CD.
Antifeedant activity was done on the mid fifth instar nymphs of two
species of locust (Locusta migratoria ~d Schistocerca gregaria). Various
concentrations of the samples (surface exudate, chloroform partition, ethyl
acetate partition, quercetin and quercetin-3-B-O-galactoside) were applied on
Whatman No. 1 filter: paper. The surface exudate were found to have high
antifeedant activity at all concentrations tested while the inner tissue
compounds showed phagostimulatory activity towards the two locust species.
UV analysis of the surface exudates and some of its pure compounds
within the uv-visible range indicated the possible use of the surface exudates
by the plant as a shield especially for the most dangerous UV-A and UV-B
radiations without interfering with the electromagnetic region of
photosynthesis. | en |
