A complex antioxidant system has been developed in mammals to relieve oxidative stress. However, excessive reactive species derived from oxygen and nitrogen may still lead to oxidative damage to tissue and organs. Oxidative stress has been considered as a conjoint pathological mechanism, and it contributes to initiation and progression of liver injury. A lot of risk factors, including alcohol, drugs, environmental pollutants and irradiation, may induce oxidative stress in liver, which in turn results in severe liver diseases, such as alcoholic liver disease and non-alcoholic steatohepatitis. Application of antioxidants signifies a rational curative strategy to prevent and cure liver diseases involving oxidative stress. Although conclusions drawn from clinical studies remain uncertain, animal studies have revealed the promising in vivo therapeutic effect of antioxidants on liver diseases. Natural antioxidants contained in edible or medicinal plants often possess strong antioxidant and free radical scavenging abilities as well as anti-inflammatory action, which are also supposed to be the basis of other bioactivities and health benefits. In this review, PubMed was extensively searched for literature research. The keywords for searching oxidative stress were free radicals, reactive oxygen, nitrogen species, anti-oxidative therapy, Chinese medicines, natural products, antioxidants and liver diseases. The literature, including ours, with studies on oxidative stress and anti-oxidative therapy in liver diseases were the focus. Various factors that cause oxidative stress in liver and effects of antioxidants in the prevention and treatment of liver diseases were summarized, questioned, and discussed.

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The Role of Oxidative Stress and Antioxidants in Liver Diseases

Overproduction of oxidants (reactive oxygen species and reactive nitrogen species) in the human body is responsible for the pathogenesis of some diseases. The scavenging of these oxidants is thought to be an effective measure to depress the level of oxidative stress of organisms. It has been reported that intake of vegetables and fruits is inversely associated with the risk of many chronic diseases, and antioxidant phytochemicals in vegetables and fruits are considered to be responsible for these health benefits. Antioxidant phytochemicals can be found in many foods and medicinal plants, and play an important role in the prevention and treatment of chronic diseases caused by oxidative stress. They often possess strong antioxidant and free radical scavenging abilities, as well as anti-inflammatory action, which are also the basis of other bioactivities and health benefits, such as anticancer, anti-aging, and protective action for cardiovascular diseases, diabetes mellitus, obesity and neurodegenerative diseases. This review summarizes recent progress on the health benefits of antioxidant phytochemicals, and discusses their potential mechanisms in the prevention and treatment of chronic diseases.

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Antioxidant Phytochemicals for the Prevention and Treatment of Chronic Diseases.

Natural antioxidants are widely distributed in food and medicinal plants. These natural antioxidants, especially polyphenols and carotenoids, exhibit a wide range of biological effects, including anti-inflammatory, anti-aging, anti-atherosclerosis and anticancer. The effective extraction and proper assessment of antioxidants from food and medicinal plants are crucial to explore the potential antioxidant sources and promote the application in functional foods, pharmaceuticals and food additives. The present paper provides comprehensive information on the green extraction technologies of natural antioxidants, assessment of antioxidant activity at chemical and cellular based levels and their main resources from food and medicinal plants.

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Natural Antioxidants in Foods and Medicinal Plants: Extraction, Assessment and Resources

The oxidative stress imposed by reactive oxygen species (ROS) plays an important role in many chronic and degenerative diseases. As an important category of phytochemicals, phenolic compounds universally exist in plants, and have been considered to have high antioxidant ability and free radical scavenging capacity, with the mechanism of inhibiting the enzymes responsible for ROS production and reducing highly oxidized ROS. Therefore, phenolic compounds have attracted increasing attention as potential agents for preventing and treating many oxidative stress-related diseases, such as cardiovascular diseases, cancer, ageing, diabetes mellitus and neurodegenerative diseases. This review summarizes current knowledge of natural polyphenols, including resource, bioactivities, bioavailability and potential toxicity.

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Resources and biological activities of natural polyphenols.

EFSA was asked to deliver a scientific opinion on acrylamide (AA) in food. AA has widespread uses as an industrial chemical. It is also formed when certain foods are prepared at temperatures above 120 °C and low moisture, especially in foods containing asparagine and reducing sugars. The CONTAM Panel evaluated 43 419 analytical results from food commodities. AA was found at the highest levels in solid coffee substitutes and coffee, and in potato fried products. Mean and 95th percentile dietary AA exposures across surveys and age groups were estimated at 0.4 to 1.9 μg/kg body weight (b.w.) per day and 0.6 to 3.4 μg/kg b.w. per day, respectively. The main contributor to total dietary exposure was generally the category ‘Potato fried products (except potato crisps and snacks)’. Preferences in home-cooking can have a substantial impact on human dietary AA exposure. Upon oral intake, AA is absorbed from the gastrointestinal tract and distributed to all organs. AA is extensively metabolised, mostly by conjugation with glutathione but also by epoxidation to glycidamide (GA). Formation of GA is considered to represent the route underlying the genotoxicity and carcinogenicity of AA. Neurotoxicity, adverse effects on male reproduction, developmental toxicity and carcinogenicity were identified as possible critical endpoints for AA toxicity from experimental animal studies. The data from human studies were inadequate for dose-response assessment. The CONTAM Panel selected BMDL10 values of 0.43 mg/kg b.w. per day for peripheral neuropathy in rats and of 0.17 mg/kg b.w. per day for neoplastic effects in mice. The Panel concluded that the current levels of dietary exposure to AA are not of concern with respect to non-neoplastic effects. However, although the epidemiological associations have not demonstrated AA to be a human carcinogen, the margins of exposure (MOEs) indicate a concern for neoplastic effects based on animal evidence. © European Food Safety Authority, 2015

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EFSA CONTAM Panel (EFSA Panel on Contaminants in the Food Chain), 2015. Scientific Opinion on acrylamide in food

The dietary consumption of grape and its products is associated with a lower incidence of degenerative diseases such as cardiovascular disease and certain types of cancers. Most recent interest has focused on the bioactive phenolic compounds in grape. Anthocyanins, flavanols, flavonols and resveratrol are the most important grape polyphenols because they possess many biological activities, such as antioxidant, cardioprotective, anticancer, anti-inflammation, antiaging and antimicrobial properties. This review summarizes current knowledge on the bioactivities of grape phenolics. The extraction, isolation and identification methods of polyphenols from grape as well as their bioavailability and potential toxicity also are included.

https://www.mdpi.com/1422-0067/11/2/622/pdf

Biological Activities of Polyphenols from Grapes

The pigmented rice has been consumed in China, Japan, and Korea for a long time. It has been used for strengthening kidney function, treating anemia, promoting blood circulation, removing blood stasis, treating diabetes, and ameliorating sight in traditional Chinese medicine. The extracts from pigmented rice are used as natural food colorants in bread, ice cream, and liquor as well as functional food. The pigmented rice is mainly black, red, and dark purple rice, and contains a variety of flavones, tannin, phenolics, sterols, tocols, γ-oryzanols, amino acids, and essential oils. Anthocyanins are thought as major functional components of pigmented rice. Several anthocyanins have been isolated and identified from the pigmented rice, including cyanidin 3-glucoside, cyanidin 3-galactoside, cyanidin 3-rutinoside, cyanidin 3,5-diglucoside, malvidin 3-galactoside, peonidin 3-glucoside, and pelargonidin 3,5-diglucoside. This review provides up-to-date coverage of pigmented rice in regard to bioactive constituents...

Phenolic Compounds and Bioactivities of Pigmented Rice

Fruit wastes are one of the main sources of municipal waste. In order to explore the potential of fruit wastes as natural resources of bioactive compounds, the antioxidant potency and total phenolic contents (TPC) of lipophilic and hydrophilic components in wastes (peel and seed) of 50 fruits were systematically evaluated. The results showed that different fruit residues had diverse antioxidant potency and the variation was very large. Furthermore, the main bioactive compounds were identified and quantified, and catechin, cyanidin 3-glucoside, epicatechin, galangin, gallic acid, homogentisic acid, kaempferol, and chlorogenic acid were widely found in these residues. Especially, the values of ferric-reducing antioxidant power (FRAP), trolox equivalent antioxidant capacity (TEAC) and TPC in the residues were higher than in pulps. The results showed that fruit residues could be inexpensive and readily available resources of bioactive compounds for use in the food and pharmaceutical industries.

https://www.mdpi.com/1422-0067/13/7/8308/pdf

Potential of Fruit Wastes as Natural Resources of Bioactive Compounds

Determination of antioxidant property and their lipophilic and hydrophilic phenolic contents in cereal grains

Edible macro-fungi are widely consumed as food sources for their flavors and culinary features. In order to explore the potential of macro-fungi as a natural resource of bioactive compounds, the antioxidant properties and polysaccharide contents of 49 edible macro-fungi from China were evaluated systematically. A positive correlation between antioxidant capacity and total phenolic content indicated that phenolic compounds could be main contributors of antioxidant capacities of these macro-fungi. Furthermore, many bioactive compounds such as gallic, homogentisic, protocatechuic, and p-hydroxybenzoic acid were identified and quantified. The macro-fungi species Thelephora ganbajun Zang, Boletus edulis Bull., Volvariella volvacea Sing, Boletus regius Krombh, and Suillus bovinus Kuntze displayed the highest antioxidant capacities and total phenolic contents, indicating their potential as important dietary sources of natural antioxidants.

Gui-Fang Deng

Papers

Biological Activities of Polyphenols from Grapes

Phenolic Compounds and Bioactivities of Pigmented Rice

Potential of Fruit Wastes as Natural Resources of Bioactive Compounds

Determination of antioxidant property and their lipophilic and hydrophilic phenolic contents in cereal grains

Antioxidant capacities, phenolic compounds and polysaccharide contents of 49 edible macro-fungi