As an intracellular enzyme that catalyzes the dehydrogenation of endogenous and exogenous alcohols, alcohol dehydrogenase (ADH) is employed to catalyze the conversion of alcohol in food into acetaldehyde to reduce the negative effects of excessive ethanol intake [1]. NAD was used as a coenzyme and ADH was used as a catalyst to convert alcohol into acetaldehyde. NADH, which is generated by NAD in the entire chemical system, has a special absorption capacity at 340 nm. At present, ADH is mainly derived from animal liver, existing the problems of poor stability, high cost, and low catalytic efficiency, so its application in the food industry is greatly limited [2]. Previous studies have demonstrated the antibacterial and anti-inflammatory properties of epigallocatechin gallate (EGCG), which accounts for 50 % of the total catechin in tea. EGCG has also been shown to eliminate free radicals, absorb ultraviolet rays, stimulate the growth of skin cells, and perform other physiological antioxidant and anti-aging functions [3]. The ultraviolet radiation inhibited the secretion of transforming growth factor-β1, induced cell cycle arrest, and down-regulated antioxidant enzymes, which caused further damage to cells. EGCG can effectively inhibit the above-mentioned damage process of human skin fibroblasts caused by ultraviolet radiation [4]. Related studies have also shown that EGCG is a potent substance for liver preservation and is capable of reducing alcohol-related liver damage [5], [6]. In addition, through multi-spectral analysis and molecular docking technology, it is finally concluded that EGCG can activate ADH activity, and interact with protein to a greater extent, and the complex formed is the most stable [7]. The EGCG-ADH can effectively increase the biological activity of ADH due to the interaction between EGCG and ADH. After interacting with small molecules, proteases are facing the problem of being absorbed and utilized by the human body. However, relative studies that how to improve the stability and prolong release efficiency of the composite enzyme have lacked because people focused on the structure and biological activity of the interaction.

By encasing several bioactive compounds in a protective carrier matrix, their stability can be maintained and the time to loss of activity extended [8]. Liposomes not only have excellent biocompatibility and are simple to absorb by the body, but their targeting and safety profile also enables them to produce effects that are precise and low in toxicity [9], [10]. The liposome system can be developed from biocompatible and biodegradable materials, such as lecithin, a phospholipid mixture widely used in cosmetics and food fields. Lecithin is widely accepted because of its good value of biocompatibility, biodegradability and easy manufacture, and it has strong scientific support for its use and application. In addition, lecithin, as a carrier of active substances, can promote its absorption in the intestine and improve its bioavailability. Lecithin also has good drug embedding ability, which can slow down the migration of hydrophilic protein in the water phase in liposomes to the medium. The barrier effect of double-layer membrane slows down the transfer and release of protein to the external environment, thus playing a better role in sustained release. Makoto et al. [11] studied that the quaternary structures of bovine liver catalase and alcohol dehydrogenase were stabilized in liposomes through the interaction with lipid membrane, and confirmed that liposomes could maintain the catalytic performance and stability of enzymes. A multifunctional liposome co-encapsulated antioxidant and anti-inflammatory drug epigallocatechin gallate (EGCG) was established and showed excellent antioxidant and anti-inflammatory effects in vitro [12]. Unfortunately, very few studies on the self-assembly of liposome complexes.

In this paper, the EGCG-ADH complex was wrapped in liposomes to form liposome by self-assembly. The structure characteristics of EGCG-ADH liposomes were studied through particle size and scanning electron microscopy (SEM). The interaction properties were investigated by fourier infrared spectroscopy (FT-IR) and 1H nuclear magnetic resonance (1H NMR). In addition, the stability and bioaccessibility of EGCG-ADH liposomes were also analyzed in vitro digestion assays. The purpose of this work is to provide evidence for the preparation and application of EGCG-ADH liposome (LC-EGCG-ADH), as well as provide new ideas for offering fresh theoretical direction in food and pharmaceutical fields.