Research progress in nutritional benefit and application of Chinese bayberry fruit

Abstract：Chinese bayberry (Myrica rubra Sieb. et Zucc.) is an important subtropical evergreen fruit crop. It is cultivated mainly in southern China, widely distributed in East China and Hunan, Guangdong, Guangxi, Guizhou and other regions. Bayberry fruit is traditional to China, characterized by bright color, sweet and sour taste, rich flavor and high nutritional value. The size of bayberry fruit is similar to a litchi, with papillas on outside surface, while the diameter of fruit varies from 1 to 1.5 cm. It is usually eaten fresh and processed into dried fruit, wine, juice and powder. The medicinal value of bayberry fruit has received more attentions in recent years and have been confirmed to be healthy for human due to its abundant sugars, vitamins, anthocyanins, fibers and other nutrient substances. Bayberry fruit is a good raw material for food therapy, with the beneficial effects of generating fluid and quenching thirst, regulating intestinal tract, killing intestinal worms, hemostasis and stopping diarrhea. In addition, current studies have shown that bayberry fruit has antioxidant, anti-inflammatory, anti-tumor, antibacterial, antiviral and hypoglycemic efficacy, cardiovascular disease prevention and other functional effects. Bayberry fruit has a pleasant sweet and sour taste. The soluble solids content in bayberry fruit is between 8.4% to 15.0%, and the total sugar and total acid contents are 8.4% and 1.2%, respectively. Bayberry fruit is a good source of phenolic acids, and the total phenolic acid content is significantlyhigher than other berries (such as blueberry, mulberry and blackcurrant). Gallic acid is the main phenolic acid in all varieties of bayberry fruit. The pink, red and nearly black colors of bayberry fruit are mainly due to the presence of anthocyanins, especially cyanidin- 3-O- glucoside, accounting for more than 95% of the total anthocyanin content of bayberry fruit. In most bayberry fruits, quercetin is the main flavonol, followed by myricetin and kaempferol. These nutrients in bayberry fruit have protective effects on liver, cardiovascular system and immune system, and can effectively prevent and treat chronic diseases. Bayberry fruit extract plays a beneficial role in the prevention or treatment of related metabolic diseases as a potential antioxidant by scavenging free radicals, and inhibiting lipid peroxidation and apoptosis. The components with anti-inflammatory properties in bayberry fruit, such as myricetin, proanthocyanidins, phenolic acids, quercetin, etc., can interact with many molecules involved in the inflammatory pathway and reduce the activity of cytokines, chemokines and inflammatory enzymes. Myricetin in the extract of bayberry fruit mainly inhibits tumor cell proliferation through the following five mechanisms: (1) Activating Hippo signaling pathway; (2) Inhibiting human hypoxanthine nucleotide dehydrogenase (hIMPDH) activities; (3) Regulating telomere G- quadruplex; (4) Regulating mitogen- activated protein kinase (MAPK) signaling pathway; (5) Activating glycogen synthase kinase-3β (GSK-3β) signaling pathway, and inhibiting β-catenin and Survivin/PCNA/cyclin D1 pathway. The extract of bayberry fruit can be used as a natural antibacterial agent to inhibit the proliferation of intestinal pathogens. It may have a significant effect on reducing blood glucose and preventing diabetes by inhibiting hepatic gluconeogenesis. And it can inhibit weight gain, improve glucose tolerance and insulin resistance, reduce serum and liver triglyceride content, and significantly improve liver macrovesicular steatosis. Bayberry fruit is not resistant to storage and transportation. It is vulnerable to collision or mechanical damage and loses water, which breeds microorganisms and causes corruption. In order to avoid the waste of resources caused by spoilage of fresh bayberry fruits, deep processing of freshly picked bayberry fruits is usually carried out to increase the economic added value of bayberry fruit and extend the shelf life and consumption cycle of bayberry products. In addition, with the deepening of research on bayberry fruit and the rapid development of bayberry industry, the processed products with fresh bayberry fruit as the main raw material are more and more favored by consumers. At present, the common processing products of bayberry fruit on the market mainly include bayberry wine, bayberry juice, dried bayberry, bayberry powder, etc. At present, the research on the functional effects of bayberry fruit and its related products is still in the initial and exploratory stage, and its potential molecular mechanism is not very clear. The types of bayberry processing product on the market are relatively few and the degree of industrialization is obviously insufficient. The focus of future research is on accelerating the process of deep processing and comprehensive utilization of by-products of bayberry fruit, continuously extending the industrial chain, and increasing added value. Based on the systematic review of recent domestic and foreign research achievements on bayberry, this paper summarizes the main nutrient compositions, biological activities and development and application of bayberry, and prospects the future development direction of bayberry industry. This article aims to provide theoretical reference for promoting in-depth research and high-value application of bayberry resources.