BINDING OF FLAVONOIDS BY POLYVINYLPOLYPYRROLIDONE

A binding assay was developed with which to monitor the binding capacity of polyvinylpolypyrrolidone (PVPP) for individual flavonoids. The assay was conducted by shaking dilute solutions of flavonoid in suspensions of PVPP in methanol/10 mM citrate buffer (1:3) at pH 6.0. The molar 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 generally bind most efficiently. When comparing flavonoids from different 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 stoichiometry and rates of binding, the incorporation of small quantities of PVPP into plant and microbial culture systems will be useful for serving to trap signal flavonoids which plants exude through their roots to communicate with microbes.