Effects of propolis on hypoxanthine-xanthine oxidase-induced toxicity in cultivated human cells and on neutrophil elastase activity

The inhibition of the proliferation rate of the immortalized human cell line ECV 304 after oxidant damage by oxygen radicals generated in a hypoxanthin-xanthine oxidase system and the protection provided by various propolis extracts was determined. Best inhibition was demonstrated by 60-80% ethanolic extracts (IC50 of approximately 2 mu g dry weight/ml) and by the ethyl acetate extract (IC50 of 6.9 mu g dry weight/ml). The beneficial effect of polar extracts was quite weak. Human neutrophil elastase activity was inhibited distinctively by ethanolic (60 to 96%) and ethyl acetate extracts (IC50 of approximately 2 mu g dry weight/ml). Both activities seem to be responsible for the anti-inflammatory effect of the extract.