BINDING OF FLAVONOIDS BY POLYVINYLPOLYPYRROLIDONE

A binding assay was developed with which to monitor the binding capaci ty of polyvinylpolypyrrolidone (PVPP) for individual flavonoids. The a ssay was conducted by shaking dilute solutions of flavonoid in suspens ions of PVPP in methanol/10 mM citrate buffer (1:3) at pH 6.0. The mol ar ratio of PVPP/flavonoid was 100:1, based on the molecular weight of the monomer unit of PVPP. Binding was rapid, and it was observed that those compounds which possess the greater number of hydroxy groups ge nerally bind most efficiently. When comparing flavonoids from differen t classes but with identical hydroxylation patterns, it was noted that flavones bind better than isoflavones, which in tum bind better than flavonones and dihydroflavonols. In light of the favorable stoichiomet ry and rates of binding, the incorporation of small quantities of PVPP into plant and microbial culture systems will be useful for serving t o trap signal flavonoids which plants exude through their roots to com municate with microbes.