Extracts of Piliostigma thonningii, the use thereof and formulations containing them

A process for the preparation of extracts from the plant Piliostigma thonningii, said plant having bark of the root, trunk and leaves, which consists of extracting the barks of the root and the trunk with aqueous acetone in a concentration varying from 9:1 to 2:8 at temperatures ranging from 25.degree. to 60.degree. C., or extracting the leaves with alcohols or ketones mixtures in a 4:6 solvent/water ratio or, alternatively, in extracting said barks and said leaves mixed together, then

• a) eliminating the solvent by concentration at a temperature below 40.degree. C.;
• b) filtering or centrifuging to remove the gummy residues of undesired substances formed during the elimination of the organic solvent to obtain a clear aqueous extract;
• c) extracting the clear aqueous extract with ethyl acetate to remove the extractable substances;
• d) subjecting the aqueous phase from step c) to chromatography on an adsorption polystyrene matrix resin column, then eluting with water and then an aliphatic low molecular weight alcohol or ketone diluted with water;
• e) partially concentrating the eluate from step d) under vacuum and at temperatures not above 60.degree. C.;
• f) evaporating the concentrate to dryness under vacuum;
• g) dissolving the residue from step f) in a small volume of methanol;
• and
• h) adding to the methanol solution from step g) an amount of methylene chloride sufficient to obtain a precipitate which is soluble in water and insoluble in aprotic solvents.