Proanthocyanidin Characterization and Bioactivity of Extracts from Different Parts of Uncaria tomentosa L. (Cat’s Claw)

Abstract

Apart from alkaloids, bioactive properties of <i>Uncaria tomentosa</i> L. have been attributed to its phenolic constituents. Although there are some reports concerning low-molecular-weight polyphenols in <i>U. tomentosa</i>, its polymeric phenolic composition has been scarcely studied. In this study, phenolic-rich extracts from leaves, stems, bark and wood (<i>n</i> = 14) of <i>Uncaria tomentosa</i> 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 <i>U. tomentosa</i> 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, <i>U. tomentosa</i> 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 <i>U. tomentosa</i> proanthocyanidins and suggest the potential value of these extracts with prospective use as functional ingredients.