Production and utilization of non-covalent dairy-based proteins complexed with date palm leave polyphenols for improving curcumin stability

This study provides insights into the non-covalent complexation of greent solvent extracted date leaf polyphenolic extracts (DLPE) with bovine and camel dairy proteins and their utilization for enhancing the photo and thermal stabilities of curcumin loaded into nano-emulsion. UV–Vis and fluorescence spectroscopies showed marked variation among bovine and camel dairy-DLPE complexes. Dairy protein-DLPE complexation improved the radical scavenging activities compared to unmodified milk proteins. Caseins-DLPE complexes showed higher total phenolic content (TPC) than whey-DLPE complexes with camel casein (CC) showing highest values. The formation of protein-polyphenol complexes was also predicted using molecular docking that suggested van der Waals interaction as a dominant force binding camel dairy protein with DLPE. Further, curcumin-loaded nanoemulsions were fabricated using dairy proteins-DLPE complexes as emulsifiers. The thermal stability of curcumin loaded in nanoemulsions was studied at different temperatures (55 °C, 75 °C and 95 °C) for varying periods of time (0–6 h) while photostability was studied by exposure to UV light for a period of 120 min. The results showed that the thermal and photostability of curcumin improved when dairy protein-DLPE complexes were used for nanoemulsion production. Camel casein-DLPE stabilized nanoemulsions imparted the highest thermal and photostabilities to curcumin while camel whey-DLPE showed the lowest retention of curcumin in nanoemulsions. In vitro digestion showed complexation of caseins with DLPE improved the bioaccesibility of curcumin. Moreover, curcumin bioaccesibility was higher for CC-DLPE (69.25%) compared to CC (49.83%) stabilized emulsions. Overall, CC-DLPE complexes demonstrated the superior performance for stabilizing the emulsion and delivering the curcumin in simulated GI tract efficiently.