The effectiveness of polyethylene glycol (PEG) and polyvinyl polypyrrolidone (PVPP) on removal of tannins from leaf extracts of selected medicinal plants in Limpopo Province

Abstract

Five selected plant species ( Balanites maughamii, Breonadia salicina, Dombeya rotundifolia, Hyperacanthus amoenus and Piliostigma thonningii) were extracted using 70 and 100% acetone and the presence of tannins were determined using radial diffusion assay. Our comparative assessment indicated that plant extracted with 100% acetone showed the highest levels of tannins as compared to 70% acetone. The highest tannin levels in both 70 and 100% acetone extracts were recorded for P. thonningii , while no tannins were detected in B. maughamii . However, addition of polyethylene glycol (PEG) and polyvinyl polypyrrolidone (PVPP) to the extraction media resulted in the reduction of tannins in all crude plant extracts, with PEG being more effective than PVPP. 1% PEG removed the highest quantity of tannins in all plant extracts, in comparison with 0.5% PEG (63.3%) and 0.5 and 1% PVPP (24.8 and 49.4%, respectively). Key words : Acetone, tannin, polyethylene glycol (PEG), polyvinyl polypyrrolidone (PVPP).