Bovine serum albumin (BSA) contains high affinity binding sites for several endogenous and exogenous compounds and has been used to replace human serum albumin (HSA), as these two compounds share a similar structure. Naringin palmitate is a modified product of naringin that is produced by an acylation reaction with palmitic acid, which is considered to be an effective substance for enhancing naringin lipophilicity. In this study, the interaction of naringin palmitate with BSA was characterised by spectroscopic and molecular docking techniques. The goal of this study was to investigate the interactions between naringin palmitate and BSA under physiological conditions, and differences in naringin and naringin palmitate affinities for BSA were further compared and analysed. The formation of naringin palmitate-BSA was revealed by fluorescence quenching, and the Stern-Volmer quenching constant (K_SV) was found to decrease with increasing temperature, suggesting that a static quenching mechanism was involved. The changes in enthalpy (ΔH) and entropy (ΔS) for the interaction were detected at −4.11±0.18 kJ·mol⁻¹ and −76.59±0.32 J·mol⁻¹·K⁻¹, respectively, which indicated that the naringin palmitate-BSA interaction occurred mainly through van der Waals forces and hydrogen bond formation. The negative free energy change (ΔG) values of naringin palmitate at different temperatures suggested a spontaneous interaction. Circular dichroism studies revealed that the α-helical content of BSA decreased after interacting with naringin palmitate. Displacement studies suggested that naringin palmitate was partially bound to site I (subdomain IIA) of the BSA, which was also substantiated by the molecular docking studies. In conclusion, naringin palmitate was transported by BSA and was easily removed afterwards. As a consequence, an extension of naringin applications for use in food, cosmetic and medicinal preparations may be clinically and practically significant, especially in the design of new naringin palmitate-inspired drugs.

Background: Pure 1, 3-diacylglycerols (1, 3-DAG) have been considered to be significant surfactants in food, cosmetics and pharmaceutical industries, as well as the effect on obesity prevention. Methods: In this study, a vacuum-driven air bubbling operation mode was developed and evaluated for the enzymatic synthesis of 1, 3-DAG of saturated fatty acids, by direct esterification of glycerol with fatty acids in a solvent-free system. The employed vacuum-driven air bubbling operation mode was comparable to vacuum-driven N₂ bubbling protocol, in terms of lauric acid conversion and 1, 3-dilaurin content. Results: Some operation parameters were optimized, and 95.3% of lauric acid conversion and 80.3% of 1, 3-dilaurin content was obtained after 3-h reaction at 50°C, with 5 wt% of Lipozyme RM IM (based on reactants) amount. Of the lipases studied, both Lipozyme RM IM and Novozym 435 exhibited good performance in terms of lauric acid conversion. Lipozyme TL IM, however, showed low activity. Lipozyme RM IM showed good operational stability in this operation protocol, 80.2% of the original catalytic activity remained after 10 consecutive batch applications. Some other 1, 3-DAG were prepared and high content was obtained after purification: 98.5% for 1, 3-dicaprylin, 99.2% for 1, 3-dicaprin, 99.1% for 1, 3-dilaurin, 99.5 for 1, 3-dipalmitin and 99.4% for 1, 3-disterin. Conclusion: The established vacuum-driven air bubbling operation protocol had been demonstrated to be a simple-operating, cost-effective, application practical and efficient methodology for 1, 3-DAG preparation.

The effects of magnetic fields on the enzymatic synthesis of naringin palmitate were studied. Both immobilized Candida Antarctica lipase B (I-CALB) and I-CALB tert-amyl alcohol solution were treated with magnetic fields of 100, 300, or 500 mT for 1, 2, or 3 h. Characteristics including the initial rate and the conversion yields after 24 h of reaction with magnetized I-CALB (M-I-CALB) and magnetized I-CALB tert-amyl alcohol solution (M-I-CALB-S) were investigated. Magnetic field application to both I-CALB and I-CALB-S influenced I-CALB activity. Enzyme activity increased for M-I-CALB and M-I-CALB-S with some intensities and durations and reached maxima at certain frequencies. Enzyme inactivation was only found with M-I-CALB exposed to a strong magnetic field (500 mT) for a long time (3 h). Unlike M-I-CALB, M-I-CALB-S exposed to a strong magnetic field for a long time (500 mT, 3 h) showed greater activity enhancement relative to I-CALB. Fourier transform infrared spectroscopy (FT-IR) results showed that the relative secondary structure content of free CALB was changed only slightly by the differing magnetic field intensities and durations. These findings should prove valuable for using magnetic fields in enzymatic reactions.