Effect of tannins on screening of plant extracts for enzyme inhibitory activity and techniques for their removal.

Ethyl acetate and aqueous extracts of tannin-containing topoisomerase inhibitory plant samples were subjected to one or more of seven tannin removal procedures, and the resulting products were subsequently evaluated for topoisomerase inhibitory activity. In most of the samples investigated, the initial activity was lost after tannin removal. It was concluded that the activity initially observed was primarily due to tannins. Procedures are presented for routinely obtaining tannin-free organic and aqueous fractions.