Characterization on the physicochemical and digestion properties of potato starch modified by the extract from...

Rhinacanthus nasutus (L.) KURZ (R. nasutus), a tropical functional tea, has a wide range of hypoglycemic applications. The slow digestion of potato starch is important for the stability of glucose spikes. However, the effects of R. nasutus on the physicochemical and digestive properties of potato starch are unknown.

Q Exactive HF liquid chromatography/mass spectrometry analysis showed that R. nasutus extract (RNE) contained naphthoquinones, fatty acids, terpenoids and others. RNE decreased the solubility and swelling of potato starch. The starch granuloid transformation and crosslinking were detected by scanning electon microscopy. The crystallinity of the starch changed obviously, the texture properties were more hardened and the viscosity was stronger. With the addition of RNE (8 g kg^-1), the digestion of starch in vitro was significantly inhibited with the proportions of fast digestible starch decreasing to 16.53% and the proportion of slow digestible starch increasing to 34.76%. IEC-6 cell assays confirmed the safety of RNE. Molecular docking results showed that RNE could interact with the amino acid residues of the digestive enzymes through hydrogen bonds, alkyl and pi-alkyl interactions, which could reduce the digestive rate of starch.

RNE was found to modify the physicochemical properties of potato starch, decreasing the solubility and swelling degree, hardening the structural properties, and increasing the viscosity, which are helpful for the edible properties of starch. The addition of RNE significantly inhibited the digestion of starch in vitro. R. nasutus and its extract might be potential candidates for new food additives. © 2025 Society of Chemical Industry.