Condensed tannins in mangosteen pericarps determined from ultraperformance liquid chromatography-mass spectrometry

Abstract

The objective of the present work was to determine the types and concentrations of condensed tannins in mangosteen pericarps. Methanol, ethanol, and acetone were employed to extract tannins from the mangosteen pericarps. The tannin extracts were depolymerized using 2-mercaptoethanol as a nucleophile. Ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) was used to structurally identify the tannins and determine their concentrations. UPLC chromatograms showed five different tannin monomers: catechin, epicatechin, catechin mercapto, catechin gallate mercapto, and epigallocatechin gallate. Catechin mercapto was the major monomer (~32 to 60 mg/g of extract). The average degree of polymerization indicated that the condensed tannins in the pericarps were mainly dimers and trimers. The experimental results showed that methanol was the most efficient extraction solvent in the present work and that UPLC-MS was a powerful technique for evaluating the condensed tannins in mangosteen pericarps in terms of qualitative and quantitative analysis.

Keywords

• condensed tannin
• depolymerization
• solvent extraction
• mangosteen pericarps
• uplc-ms