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Open AccessArticle

Polyphenolic Composition and Antioxidant Activity of Uncaria tomentosa Commercial Bark Products

1
Department of Chemistry, University of Costa Rica (UCR), Sede Rodrigo Facio, San Pedro de Montes de Oca, San José 2060, Costa Rica
2
Department of Biology, Technological University of Costa Rica (TEC), Cartago 7050, Costa Rica
3
Department of Civil Engineering, University of Toronto, 35 St. George Street, Toronto, ON, M5S 1A4, Canada
4
Department of Economics, State University of New York, SUNY at Binghamton, 400 Vestal Pkwy E, Binghamton, NY 13902, USA
5
Institute of Food Science Research (CIAL), Spanish National Research Council (CSIC), C/Nicolás Cabrera 9, 28049 Madrid, Spain
*
Author to whom correspondence should be addressed.
Antioxidants 2019, 8(9), 339; https://doi.org/10.3390/antiox8090339
Received: 30 June 2019 / Revised: 11 August 2019 / Accepted: 14 August 2019 / Published: 23 August 2019
(This article belongs to the Special Issue Phenolic Profiling and Antioxidant Capacity in Plants)
Uncaria tomentosa, which is widely commercialized as an herbal medicine, constitutes an important source of secondary metabolites with diverse biological activities. For instance, we have previously reported, for the first time, of a polyphenolic profile rich in proanthocyanidins from extracts of U. tomentosa plants, as well as their antioxidant capacity, antimicrobial activity on aerial bacteria, and cytotoxicity on cancer cell lines. These promising results prompted this research to evaluate the polyphenolic contents of U. tomentosa commercial products. We report a detailed study on the polyphenolic composition of extracts from U. tomentosa bark products (n = 18) commercialized in Costa Rica and Spain. Using HPLC-DAD/TQ-ESI-MS, a total of 25 polyphenolic compounds were identified, including hydroxybenzoic and hydroxycinnamic acids, flavan-3-ol monomers, procyanidin dimers, procyanidin trimers, as well as propelargonidin dimers. Our findings on the polyphenolic profile for all commercial samples show analogous composition to previous reports on U. tomentosa bark material, for instance a 41–49% content of procyanidin dimers and the presence of propelargonidin dimers (8–15%). However, most of the 18 commercial samples exhibit low proanthocyanidin contents (254.8–602.8 µg/g), more similar to previous U. tomentosa inner bark reports, while some exhibit better results, with one sample (SP-2) showing the highest contents (2386.5 µg/g) representing twice the average value of all 18 commercial products. This sample also exhibits the highest total phenolics (TP) and total proanthocyanidins (PRO) contents, as well as the highest Oxygen Radical Absorbance Capacity (ORAC) value (1.31 µg TE/g). One-way Analysis of Variance (ANOVA) with a Tukey post hoc test indicated significant difference (p < 0.05) between products from Costa Rica and Spain for TP and PRO findings, with samples from Spain exhibiting a higher average value. In addition, Pearson correlation analysis results showed a positive correlation (p < 0.05) between TP, PRO, and ORAC results, and an especially important correlation between ORAC antioxidant values and procyanidin dimers (r = 0.843, p < 0.05), procyanidin trimers (r = 0.847, p < 0.05), and propelargonidin dimers (r = 0.851, p < 0.05) contents. Finally, Principal Component Analysis (PCA) results indicated some variability in the composition regardless of their origin. However, only one sample (SP-2) stands out significatively, showing the highest PC1 because of its particularly high proanthocyanidins contents, which could be attributed to the 15% bark polyphenolic extract labeled in this commercial product, which differentiate this sample from all other 17 commercial samples. Therefore, our findings confirmed previous results on the value of extracts in the elaboration of potential commercial products from U. tomentosa, rich in proanthocyanidins and exhibiting high antioxidant activity. View Full-Text
Keywords: Uncaria tomentosa; polyphenols; medicinal herbs; proanthocyanidins; hydroxybenzoic acids; hydroxycinnamic acids; HPLC; TQ-ESI-MS Uncaria tomentosa; polyphenols; medicinal herbs; proanthocyanidins; hydroxybenzoic acids; hydroxycinnamic acids; HPLC; TQ-ESI-MS
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MDPI and ACS Style

Navarro, M.; Arnaez, E.; Moreira, I.; Hurtado, A.; Monge, D.; Monagas, M. Polyphenolic Composition and Antioxidant Activity of Uncaria tomentosa Commercial Bark Products. Antioxidants 2019, 8, 339.

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