Some dietary supplements, so-called '
starch-blockers', used to control
overweight, are based on the
protein concentrate of the kidney bean, known to contain high levels of the
alpha-amylase inhibitor
phaseolamin, which may hinder the digestion of complex
carbohydrates, thereby promoting or supporting
weight loss. Currently, methods to determine the levels of
alpha-amylase inhibitor are based on the measurement of
alpha-amylase activity using colorimetric methods that cannot be applied to dietary supplements because they are
complex mixtures of different ingredients that may interfere with the measurement. The aim of this study was to develop an alternative method to determine the level of
phaseolamin in dietary supplements, using high-performance
anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD) to measure the amount of
maltose resulting from the action of the
enzyme porcine
alpha-amylase on soluble
starch in the presence and absence of the inhibitor. The assay described proved sensitive and accurate for use with both dietary supplements and raw materials.