Augmenting the antioxidant, anti-bacterial and anti-carcinogenic potential of Terminalia chebula and Terminalia bellirica after tannin acyl hydrolase mediated biotransformation

Abstract

Tannins, the fourth most abundant plant compounds, comprise condensed and hydrolysable types. Proanthocyanidins are flavan-3-ol polymers, while hydrolysable tannins, categorized as gallotannins and ellagitannins, form esters of gallic/ellagic acid and poly-ol. Tannin acyl hydrolase catalyzes hydrolysable tannin breakdown, yielding gallic acid derivatives with antibacterial, anti-hyperglycemic, anti-inflammatory, antioxidant, anti-carcinogenic properties. In this study, we explored hydrolysable tannins in extracts from Terminalia chebula and Terminalia bellirica, focusing on their phenolic and tannin content, as well as enzymatic and biological activities. Quantitative assessments for Total Phenol Content (TPC), Tannic Acid Content (TAC), and Hydrolysable Tannin Content (HTC) were carried out with Terminalia chebula displaying maximum amount of all three i.e. 291.9mg GAE/g DW TPC, 266.7 mgTAE/g DW TAC and 246.6 mg TAE/g DW HTC. LCMS-MS analysis revealed 8 and 13 gallic acid derivatives from T. bellirica and T. chebula, respectively after enzymatic hydrolysis. Following enzymatic treatment, the IC50 values for T. bellirica were slightly higher than T. chebula. The tannase hydrolysed T. chebula demonstrated the highest zone of inhibition against E. coli whereas the un-hydrolysed T. chebula showed minimal inhibition across all four bacterial cultures under study. The hydrolysed extract of T. chebula exhibited significant cytotoxicity after a 20-min hydrolysis, demonstrating a substantial effect with a minimal IC50 value of 83.56 μg/ml against HCT-116 cell line. Our study quantitatively highlights the enhanced bioactive properties conferred by enzymatic hydrolysis of hydrolysable tannins and considerable health benefits associated with these compounds.