Phenolics are broadly distributed in the plant kingdom and are the most abundant secondary metabolites of plants. Plant polyphenols have drawn increasing attention due to their potent antioxidant properties and their marked effects in the prevention of various oxidative stress associated diseases such as cancer. In the last few years, the identification and development of phenolic compounds or extracts from different plants has become a major area of health- and medical-related research. This review provides an updated and comprehensive overview on phenolic extraction, purification, analysis and quantification as well as their antioxidant properties. Furthermore, the anticancer effects of phenolics in-vitro and in-vivo animal models are viewed, including recent human intervention studies. Finally, possible mechanisms of action involving antioxidant and pro-oxidant activity as well as interference with cellular functions are discussed.

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Plant phenolics: extraction, analysis and their antioxidant and anticancer properties.

Bioactive compounds in foods: their role in the prevention of cardiovascular disease and cancer

Phenolics and polyphenolics in foods, beverages and spices: Antioxidant activity and health effects – A review

Natural antioxidants from residual sources.

Bioavailability and bioefficacy of polyphenols in humans. II. Review of 93 intervention studies

Objective: The goal of this work is to determine the amount and quality of phenol antioxidants in dried fruits and compare them with the corresponding fresh fruits; to compare the nutrients in fresh and dried fruits; to determine if figs are a source of in vivo antioxidants when eaten.Methods: Commercial samples of dried fruits and fresh fruits were compared in the in vitro studies using a colorimetric method to measure phenolic antioxidants. The quality of the antioxidants was measured by inhibition of lower density lipoprotein oxidation. Ten normal free-living subjects were tested in the human study. Fasting subjects were given 40 g of figs with or without a carbonated beverage and the plasma antioxidant capacity was measured for six hours using the trolox equivalent antioxidant capacity assay.Results: Dates have the highest concentration of polyphenols among the dried fruits. Figs and dried plums have the best nutrient score among the dried fruits, and dates among the fresh fruits. Processing to produc...

Dried fruits: excellent in vitro and in vivo antioxidants.

Effects of cocoa powder and dark chocolate on LDL oxidative susceptibility and prostaglandin concentrations in humans

Phenol Antioxidant Quantity and Quality in Foods: Cocoa, Dark Chocolate, and Milk Chocolate

The methods described in this article are quick, simple, and inexpensive to perform. The Folin quantitation method can determine both free and total polyphenol antioxidants in foods and beverages as described, as well as botanical extracts. This assay may also be used to estimate the daily per capita consumption of polyphenols in foods. The dose-response in vitro lower density lipoprotein antioxidant activity measurement (IC50) can be employed to compare antioxidants as pure compounds, or in mixtures after quantitating the polyphenols. The ex vivo lipoprotein-binding antioxidant activity can be measured simply and rapidly to determine possible in vivo binding of pure compounds or extracts from foods. Supplementation and epidemiology studies can utilize the rapid and inexpensive affinity column isolation method of lower density lipoproteins for the determination of lipoprotein oxidative susceptibility.

Determination of quantity and quality of polyphenol antioxidants in foods and beverages

It is well known that eating fruits and vegetables lowers the risk of chronic diseases such as heart disease and cancer. The question of what is/are the active ingredient(s) is still unresolved. The initial hypothesis was that the antioxidant vitamins were responsible. However, recently the polyphenols have been investigated since they have been found to have beneficial properties such as being strong antioxidants. We measured the polyphenol content of citrus juices by an oxidation-reduction colorimetric method (Folin) using catechin as the standard. The order was tangerine juice > grapefruit juice > orange juice. The antioxidant contribution of ascorbic acid was measured by the difference in Folin reactive content following removal by ascorbate oxidase. Ascorbate contributed 56 to 77% of the antioxidant content of orange juice, 46% of the single tangerine juice measured, and 66 to 77% of grapefruit juices. Polyphenol quality in the juices was analyzed by using the inhibition of lower density lipoprotein oxidation promoted by cupric ion, an in vitro model of heart disease. Quality decreased in the following order: orange juice > grapefruit juice > tangerine juice. In orange juice polyphenols accounted for 84–85% of antioxidant quality. The pure polyphenol hesperidin, which is common in juices, ascorbic acid, and the citrus juices, were not able to bind with LDL+VLDL and protect it from oxidation. In a hamster model of atherosclerosis, the juices were able to significantly inhibit atherosclerosis and lowered cholesterol and triglycerides. Ascorbic acid alone in the dose provided by the juices was found to have the same effect on atherosclerosis. However, the polyphenols in the citrus juices are responsible for the hypolipemic effects. In a crossover study neither 200 mg of vitamin C alone or in orange juice had an in vivo antioxidant effect on either plasma or LDL+VLDL, and no hypolipemic effects in 8 normal human subjects.

John Proch

Papers

Dried fruits: excellent in vitro and in vivo antioxidants.

Effects of cocoa powder and dark chocolate on LDL oxidative susceptibility and prostaglandin concentrations in humans

Phenol Antioxidant Quantity and Quality in Foods: Cocoa, Dark Chocolate, and Milk Chocolate

Determination of quantity and quality of polyphenol antioxidants in foods and beverages

Polyphenol Antioxidants in Citrus Juices: in vitro and in vivo Studies Relevant to Heart Disease