Proanthocyanidin Characterization, Antioxidant and Cytotoxic Activities of Three Plants Commonly Used in Traditional Medicine in Costa Rica: Petiveria alliaceae L., Phyllanthus niruri L. and Senna reticulata Willd.

Abstract

The phenolic composition of aerial parts from <i>Petiveria alliaceae</i> L., <i>Phyllanthus niruri</i> L. and <i>Senna reticulata</i> Willd., species commonly used in Costa Rica as traditional medicines, was studied using UPLC-ESI-TQ-MS on enriched-phenolic extracts. Comparatively, higher values of total phenolic content (TPC), as measured by the Folin-Ciocalteau method, were observed for <i>P. niruri</i> extracts (328.8 gallic acid equivalents/g) than for <i>S. reticulata</i> (79.30 gallic acid equivalents/g) whereas <i>P. alliaceae</i> extract showed the lowest value (13.45 gallic acid equivalents/g). A total of 20 phenolic acids and proanthocyanidins were identified in the extracts, including hydroxybenzoic acids (benzoic, 4-hydroxybenzoic, gallic, prochatechuic, salicylic, syringic and vanillic acids); hydroxycinnamic acids (caffeic, ferulic, and p-coumaric acids); and flavan-3-ols monomers [(+)-catechin and (-)-epicatechin)]. Regarding proanthocyanidin oligomers, five procyanidin dimers (B1, B2, B3, B4, and B5) and one trimer (T2) are reported for the first time in <i>P. niruri</i>, as well as two propelargonidin dimers in <i>S. reticulata</i>. Additionally, <i>P. niruri</i> showed the highest antioxidant DPPH and ORAC values (IC₅₀ of 6.4 μg/mL and 6.5 mmol TE/g respectively), followed by <i>S. reticulata</i> (IC₅₀ of 72.9 μg/mL and 2.68 mmol TE/g respectively) and <i>P. alliaceae</i> extract (IC₅₀ >1000 μg/mL and 1.32 mmol TE/g respectively). Finally, cytotoxicity and selectivity on gastric AGS and colon SW20 adenocarcinoma cell lines were evaluated and the best values were also found for <i>P. niruri</i> (SI = 2.8), followed by <i>S. reticulata</i> (SI = 2.5). Therefore, these results suggest that extracts containing higher proanthocyanidin content also show higher bioactivities. Significant positive correlation was found between TPC and ORAC (<i>R</i>² = 0.996) as well as between phenolic content as measured by UPLC-DAD and ORAC (<i>R</i>² = 0.990). These findings show evidence for the first time of the diversity of phenolic acids in <i>P. alliaceae</i> and <i>S. reticulata</i>, and the presence of proanthocyanidins as minor components in latter species. Of particular relevance is the occurrence of proanthocyanidin oligomers in phenolic extracts from <i>P. niruri</i> and their potential bioactivity.