The Biomedical Functions and Related Mechanisms of Anthocyanin-Rich Extracts from Different Plant-Based Food

The Functions and Mechanisms Abstract Anthocyanins are a group of natural edible functional pigments, which not only provide the attractive color for plant, but also generate biomedical functions on various chronic diseases. Dietary interventions of anthocyanins are being investigated extensively which are associated with the prevention of chronic disorders and diseases. This review has summarized the latest research on the biomedical functions (including cholesterol control, asthma inflammation inhibition, retinal cells and liver fibrosis protection) of anthocyanin extracts from various food-based plants. The mechanisms of anthocyanin biomedical activity were attributed by the antioxidative, anti-inflammatory, and anti-proliferative properties, as well as the ability to regulate gene expression and metabolic pathways.


Introduction
Anthocyanins, a class of water-soluble pigments widely found in plants [1]. They have the typical structure of flavonoids and are derivatives of 2-phenylbenzocchidic cations with C6-C3-C6 as the basic backbone. Anthocyanins are glycoside derivatives of anthocyanidins. There are more than 300 different anthocyanins in nature. They were found in a variety of fruits and vegetables such as purple sweet potato, cranberry, cranberry, blueberry, grape, elderberry, black currant, purple carrot and red cabbage, ranging in color from red to blue [1]. The types of anthocyanins mainly include delchindin, cyanidin, petunidin and peonidin.
Anthocyanin has been already reported about its antioxidant ability and its effect on some chronic diseases. Epidemiological studies have found that long-term intake of plant foods rich in flavonoids can reduce the incidence of chronic cardiovascular diseases (CVD) and generate anti-mutation and anti-tumor activities [2]. For example, red wine anthocyanin extracts had strong inhibitory activity against the growth of colon cancer cells HCT-15 and gastric cancer cells AGS [3]. Also, anthocyanin-rich extracts have exhibited great performance on attenuating low density lipoproteins oxidation, lipid peroxidation, dyslipidemia and reduced levels of CVD molecular biomarkers as well as improved total plasma antioxidant capacity [4]. Since the exploration of anthocyanin bioactivity continuously progresses, more biomedical functions of anthocyanin have been discovered. Therefore, in this review, the latest research on the biomedical functions of anthocyanin extracts such as the protective effect on asthma, hyperlipidemia, retinal damage etc. and the related mechanisms were introduced and discussed. It will provide essential information for develop functional food or dietary supplements using anthocyanin extracts.

Cholesterol regulation
The physiological activity of cholesterol metabolism of

Asthma inflammation inhibition
In recent years, inhibition of Th2 cell activation in the treatment of asthma has become a research concern. Anthocyanins are glycosides formed by the combination of anthocyanins and various sugars by sugar bonds. Generally, Th2 cells, mast cells, monocytes, lymphocytes, eosinophils and neutrophils are the main inflammatory cells, which release cytokines and play important roles in asthma [10]. These cytokines could also induce the release of histamine and leukotriene resulting in airway hyperresponsiveness. Specially, Th2 cytokines, such as L-4 and IL-5, regulate the body's immune response, inducing IgE production and chemotactic eosinophils [11]. Thus, the pathogenesis of asthma is related to the imbalance of Thl/Th2 cells. In the study of Arora

Retinal cells protection
Bulberry anthocyanin extract protected retinal pigment epithelium (RPE) cells from damage induced by H2O2, as indicated by morphological observation [13]. Also, anthocyanins from blueberries are capable of reducing A2E-epoxidation by quenching singlet oxygen and protecting RPE cells from A2E cytotoxicity [14].

Apoptosis in the RPE cells treated by anthocyanin extracts decreased
approximately three times compared with control group. Thus, the anthocyanin extracts could inhibit oxidative damage induced by interleukin-6 (IL-6) and inhibit the expression of alpha smooth muscle motor protein (α-SMA) and other proteins [16].

Effect of anthocyanin extracts on liver fibrosis in mice:
Anthocyanin extracts have a regulatory effect on the body weight of mice and has a significant inhibitory effect on the abnormal increase of liver coefficient in liver fibrosis mice [17]. It showed a significant protective effect on liver function indexes in the blood and liver tissue of liver fibrosis mice. Enhanced levels of antioxidant related enzymes (SOD, GSH-PX) also indicated that anthocyanin extracts can alleviate the symptoms of liver fibrosis in a dose-dependent manner [18]. Meanwhile, the expression of inflammatory factors (IL-1, IL-6, TNF-a COX-2) in liver tissue were inhibited. The inhibition of the expression of TGF-β1 and P-Smad2 protein in the TGF-β/ Smad signaling pathway were observed with the treatment of anthocyanin extract during liver fibrosis [19,20].
The above results suggested that inhibition of liver fibrosis by anthocyanin extracts may be achieved through the TGF-β/ Smad signaling pathway and reduce the accumulation of inflammation factors in liver tissue, thereby achieving the effect of delaying liver fibrosis.

Conclusion
It has been widely studied that anthocyanin extracts are associated with multiple bioactivities including scavenging free radical damage/oxidative stress, protecting cells, tissues and vital organs. This review has reported the latest biomedical functions of anthocyanin rich extracts such as antiglycation effect, cholesterol regulation, retinal cells protection and positive effect on asthma inflammation and liver fibrosis. It would provide essential information for consumers, healthcare providers, and the food and health industry to understand the relationship between anthocaynins and health. It is highly recommended that daily intake can mitigate the risk of diseases.