Fast LC–MS analysis of gallotannins from mango (Mangifera indica L.) kernels and effects of methanolysis on their antibacterial activity and iron binding capacity

Abstract

Mango (Mangifera indica L.) kernels were successively extracted with hexane and methanol and the effects of extraction on the profile of gallotannins as well as on their antimicrobial activity and iron-binding capacity were determined. A new method based on fast liquid chromatography with diode array and mass spectrometric detection was developed which allowed the separation of gallotannins in less than 7min. Gallotannins remained stable during Soxhlet extraction with hexane. Methanolysis led to the degradation of highly galloylated tannins to yield penta-O-galloylglucose and methyl gallate. The antimicrobial activity of the extracts was not affected by the compositional change, whereas the iron binding capacity increased with increasing amounts of methyl gallate. The less complex profile of antimicrobial compounds obtained after methanolysis compared to the crude extract will facilitate the standardization of extracts and their application in target products.