Study of the Specificity of Cross-Povidone (PVPP) as binding agent in the quantification of polyphenolic compounds

Abstract

O polímero polivinilpirrolidona (PVPP) proporciona uma alternativa analítica ao invés do pó-de-pele e caseína, como um agente complexante na quantificação de taninos. Neste trabalho foi estudado a especificidade do PVPP em complexar com compostos polifenólicos, na presença de rutina. Os ácidos gálico e tânico, catequina e pirogalol foram utilizados como substâncias de referência (PRS), junto com o extrato aquoso das folhas do Psidium guajava L. A especificidade da complexação foi avaliada pelo método espectrofotométrico e por cromatografia líquida de alta eficiência (CLAE) com arranjo de diodos (DAD). As análises para a mistura das PRS e rutina, demonstraram claramente que a complexação com PVPP não é uma reação específica e independe da quantidade de polímero utilizada. As análises por CLAE-DAD do extrato de Psidium guajava revelaram picos característicos de flavonóides, além de catequina e ácido gálico. Todos os picos destes flavonóides, catequina e ácido gálico decresceram quando adicionou-se o PVPP. Isto confirma a falta de especificidade. Desde que a ligação PVPP-polifenóis depende de características estruturais particulares, a extensão desses resultados a outras espécies vegetais deve ser evitada.Cross-povidone, or polyvinylpyrrolidone (PVPP) affords an analytical alternative instead of hide-powder and casein as binding agent in the content assay of vegetable tannins. In this work we studied the specificity of PVPP to bind polyphenolics in the presence of flavonoids. Gallic acid, tannic acid, catechin and pyrogallol were used as polyphenolic reference substances (PRS), along with an aqueous extract from Psidium guajava L. leaves. The binding specificity was assayed by UV-Vis and High Performance Liquid Chromatography-Photodiode array (HPLC-PDA) methods. The analyses of PRS-rutin mixtures showed clearly that PVPP binding is a non-specific reaction, unrelated to the amount of PVPP used. HPLC-PDA analysis revealed peaks which could be characterized as flavonoids in the Psidium guajava extract, beside catechin and gallic acid. All these flavonoids, catechin and gallic acid peaks decreased as PVPP was added; this confirms the lack of specificity. Since the polyphenolic-PVPP reaction depends on specific structural features, any extensive conclusion should be avoided.

Phenolic Composition and Biological (Anti Diabetic and Antioxidant) Activities of Different Solvent Extracts of an Endemic Plant (Heliotropium Strigosum)

“…In current study total phenolic contents of methanol extract and different solvent (Hexane, chloroform, ethyl acetate and aqueous) fractions of H. strigosum were determined using Folin-Ciocalteu method, which is described in different pharmacopieias 18 . The reaction is based upon the fact that phosphomolybedate and phosphotungstate in the reaction mixture react with phenolic compounds in the plant sample and generate a blue chromophere that had maximum light absorption at 760 nm 19 .…”

Adsorption of isoflavones onto PVPP in the presence of a soy matrix

“…In its cross-linked form, this polymer is water-insoluble, and has the ability to bind polyphenolic components mainly based on hydrogen bonds and hydrophobic interaction. For the formation of hydrogen bonds, the phenolic molecule should be present in its protonated form [4,5]. This can be the case at neutral pH, but PVPP is often used at lower pH to ensure protonation of the adsorbate.…”

“…This can be the case at neutral pH, but PVPP is often used at lower pH to ensure protonation of the adsorbate. Not only the state of protonation of the adsorbate is important; the number of phenolic hydroxyl groups available for hydrogen bonding seems to play a large role as well [5,6].…”

“…the pure polyphenol and PVPP in a solvent) [4,6], or with the purpose of using PVPP as an adsorbent for analytical assays [5]. However, adsorption may take place in a different manner if components are in a complex solid-liquid system [10,11].…”

Evaluating potential alternatives to potassium caseinate for white wine fining: Effects on physicochemical and sensory characteristics

“…PVPP could be used alone or in combination with much smaller quantities of casein and still effectively reduce wine oxidation through removal of polyphenols in reduced and oxidised (quinones and quinone methides) forms, which includes simple phenolic acids and flavonoids. PVPP binds (poly)phenolics by hydrogen bonding between the PVPP-carbonyl group with the phenolic-hydroxyl groups (Donel, Bécard, & Irwin, 1993;Verza, Pavei, & Ortega, 2008) of both simple phenolics and flavonoids. Casein directly inhibits the oxidation of (poly)phenols to quinones/quinone methides and may also remove these highly reactive oxidation products by nonenzymatic formation of caseinequinone conjugates (Hurrel, Finot, & Cuq, 1982;Kroll, Rawel, & Rohn, 2003;Rawel, Kroll, & Kulling, 2007;Ribéreau-Gayon, Glories, Maujaen, & Dubourdieu, 1999).…”