Abstract
Apart from alkaloids, bioactive properties of Uncaria tomentosa L. have been attributed to its phenolic constituents. Although there are some reports concerning low-molecular-weight polyphenols in U. tomentosa, its polymeric phenolic composition has been scarcely studied. In this study, phenolic-rich extracts from leaves, stems, bark and wood (n = 14) of Uncaria tomentosa plants from several regions of Costa Rica were obtained and analysed in respect to their proanthocyanidin profile determined by a quadrupole-time-of-flight analyser (ESI-QTOF MS). Main structural characteristics found for U. tomentosa proanthocyanidins were: (a) monomer composition, including pure procyanidins (only composed of (epi)catechin units) and propelargonidins (only composed of (epi)afzelechin units) as well as mixed proanthocyanidins; and (b) degree of polymerization, from 3 up to 11 units. In addition, U. tomentosa phenolic extracts were found to exhibit reasonable antioxidant capacity (ORAC (Oxygen Radical Absorbance Capacity) values between 1.5 and 18.8 mmol TE/g) and antimicrobial activity against potential respiratory pathogens (minimum IC50 of 133 µg/mL). There were also found to be particularly cytotoxic to gastric adenocarcinoma AGS and colon adenocarcinoma SW620 cell lines. The results state the particularities of U. tomentosa proanthocyanidins and suggest the potential value of these extracts with prospective use as functional ingredients.
Highlights
IntroductionProanthocyanidins are condensed flavan-3-ols with a high degree of structure variability, depending on their constituent monomers structure (propelargonidins, procyanidins, prodelphinidins, profisetinidins and prorobinetinidins), their interflavanic bond type (type A and type B proanthocyanidins), Antioxidants 2017, 6, 12; doi:10.3390/antiox6010012 www.mdpi.com/journal/antioxidantsAntioxidants 2017, 6, 12 and its degree of polimerization (DP)
Proanthocyanidins are condensed flavan-3-ols with a high degree of structure variability, depending on their constituent monomers structure, their interflavanic bond type, Antioxidants 2017, 6, 12; doi:10.3390/antiox6010012 www.mdpi.com/journal/antioxidantsAntioxidants 2017, 6, 12 and its degree of polimerization (DP)
Our previous studies on U. tomentosa [10,15] focused on the LC-ESI MS identification of low molecular weight polyphenols and demonstrated for the first time the occurrence of propelargonidin dimers in U. tomentosa extracts from different part plants
Summary
Proanthocyanidins are condensed flavan-3-ols with a high degree of structure variability, depending on their constituent monomers structure (propelargonidins, procyanidins, prodelphinidins, profisetinidins and prorobinetinidins), their interflavanic bond type (type A and type B proanthocyanidins), Antioxidants 2017, 6, 12; doi:10.3390/antiox6010012 www.mdpi.com/journal/antioxidantsAntioxidants 2017, 6, 12 and its degree of polimerization (DP). Proanthocyanidins have become of high interest because of their biological properties, such as antioxidant, anti-inflammatory and anticancerigen properties with further investigation of interest due to proanthocyanidins potential use in cancer prevention [1]. There are numerous scientific reports on U. tomentosa bioactivity, comprising anti-inflammatory and antioxidant properties, and protective effects against cancer, as well as positive effects in the cardiovascular, central nervous and locomotor systems [2]. These bioactive properties of U. tomentosa have been attributed mainly to its alkaloid contents [3], it has been reported that some properties such as its antioxidant effect could be related to its phenolic contents [4].
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