Morus alba L. leaves modulate sweet (TAS1R) and bitter (TAS2R) taste in the studies on human receptors – is it a new perspectives of white mulberry leaves utilization in food production?

Abstract

From the nutritional point, the main direction for white mulberry (Morus alba L.) elements utilization so far is to create dietary supplements or functional foods for diabetics or over-weight patients. Leaves are widely known as a valuable source of bioactive compounds responsible for its antioxidant and antidiabetic effects, both in animals and humans. We found that processed leaves can be also considered as a bitter and/or sweet taste modulators – important aspect in designing of new functional foods. The aim of the study was to validate the inhibitory effect of Morus alba L. on the TAS2R3 and TAS2R13 bitter taste and TSA1R2/TSA1R3 receptors, and determine the changes that conditioning process caused in such receptors. Effect on the receptors was evaluated in specially transfected HEK293T cells, and the inhibition ratio was measured using the calcium release test. Moreover, the stability of phenolic acids and flavonols in the simulated intestinal in vitro digestion process was determined. Results showed that the tested Morus alba leaf extracts were rich in gallic, chlorogenic and caffeic acids together with rutin and quercetin 3-(6-malonyl)-glucoside, while the conditioning process positively affected on their amount. Mostly identified phenolics were reduced as a result of in vitro digestion. In taste receptors test, it was found that the phytochemicals from conditioned Morus alba leaf extract enhanced sweet taste, together with reduction of bitter taste receptors activity in some cases. To conclude, we found Morus alba, especially conditioned for 4 hours, seems to be valuable modulator of taste, what should be considered in future as a crucial reason for its new utilization.