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& A reversed-phase LC method was developed and validated for the separation and assay of the main polyphenols in extracts from barks of Uncaria tomentosa. The LC method consists of a RP-18 column, in gradient mode (trifluoroacetic acid-methanol) using chlorogenic acid, caffeic acid, and rutin as externals standards and UV-detection at 325 nm. The method showed a good specificity, linearity, precision, and accuracy for standards compounds and for the five major peaks from bark extract. Calibration curves were linear with determination coefficients higher than 0.99. The repeatability and intermediary precision for the five major peaks ranged from 1.09 to 5.60 % and 1.25 to 6.28%, respectively. The accuracy values for chlorogenic acid, caffeic acid, and rutin in the bark extract were 97.17, 98.84, and 101.78%, respectively. The LC method was applied successfully to one commercial spray-dried and four different freeze-dried extracts produced from barks and roots of U. tomentosa.

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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.

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The validated LC-UV method was shown to be linear, precise, accurate and to cover several saponins previously isolated from Ilex species and could be applied for the quality control of unripe fruit saponins.