* 1 Food sources
* 1.1 Regulatory guidance
* 2 Vitamins
* 3 Vitamin cofactors and minerals
* 4 Hormones
* 6 Natural phenols
* 6.1 Flavonoids * 6.2 Phenolic acids and their esters * 6.3 Other nonflavonoid phenolics
* 7 Other potential organic antioxidants * 8 See also * 9 References * 10 External links
Main article: oxygen radical absorbance capacity
In the following discussion, the term "antioxidant" refers mainly to
non-nutrient compounds in foods, such as polyphenols, which have
antioxidant capacity in vitro and so provide an artificial index of
antioxidant strength – the ORAC measurement. Other than for dietary
antioxidant vitamins – vitamin A , vitamin C and vitamin E – no
food compounds have been proved with antioxidant efficacy in vivo .
Accordingly, regulatory agencies like the Food and Drug Administration
of the United States and the
European Food Safety Authority
POLYPHENOLS IN FOODS
Many common foods contain rich sources of polyphenols which have antioxidant properties only in test tube studies. As interpreted by the Linus Pauling Institute , dietary polyphenols have little or no direct antioxidant food value following digestion. Not like controlled test tube conditions, the fate of flavones or polyphenols in vivo shows they are poorly absorbed and poorly conserved (less than 5%), so that most of what is absorbed exists as metabolites modified during digestion, destined for rapid excretion.
Spices, herbs, and essential oils are rich in polyphenols in the plant itself and shown with antioxidant potential in vitro . Typical spices high in polyphenols (confirmed in vitro) are clove , cinnamon , oregano , turmeric , cumin , parsley , basil , curry powder , mustard seed , ginger , pepper , chili powder , paprika , garlic , coriander , onion and cardamom . Typical herbs are sage , thyme , marjoram , tarragon , peppermint , oregano , savory , basil and dill weed .
Dried fruits are a good source of polyphenols by weight/serving size as the water has been removed making the ratio of polyphenols higher. Typical dried fruits are pears, apples, plums, peaches, raisins, figs and dates. Dried raisins are high in polyphenol count. Red wine is high in total polyphenol count which supplies antioxidant quality which is unlikely to be conserved following digestion (see section below).
Deeply pigmented fruits like cranberries, blueberries, plums, blackberries, raspberries, strawberries, blackcurrants, figs, cherries, guava, oranges, mango, grape juice and pomegranate juice also have significant polyphenol content.
Typical cooked vegetables rich in antioxidants are artichokes , cabbage , broccoli , asparagus , avocados , beetroot and spinach .
Nuts are a moderate source of polyphenol antioxidants. Typical nuts are pecans , walnuts , hazelnuts , pistachio , almonds , cashew nuts , macadamia nuts and peanut butter .
Sorghum bran, cocoa powder, and cinnamon are rich sources of procyanidins, which are large molecular weight compounds found in many fruits and some vegetables. Partly due to the large molecular weight (size) of these compounds, their amount actually absorbed in the body is low, an effect also resulting from the action of stomach acids, enzymes and bacteria in the gastrointestinal tract where smaller derivatives are metabolized and prepared for rapid excretion.
Despite the above discussion implying that ORAC-rich foods with polyphenols may provide antioxidant benefits when in the diet, there remains no physiological evidence that any polyphenols have such actions or that ORAC has any relevance in the human body.
On the contrary, research indicates that although polyphenols are good antioxidants in vitro , antioxidant effects in vivo are probably negligible or absent. By non-antioxidant mechanisms still undefined, polyphenols may affect mechanisms of cardiovascular disease or cancer.
The increase in antioxidant capacity of blood seen after the consumption of polyphenol-rich (ORAC-rich) foods is not caused directly by the polyphenols, but most likely results from increased uric acid levels derived from metabolism of flavonoids. According to Frei, "we can now follow the activity of flavonoids in the body, and one thing that is clear is that the body sees them as foreign compounds and is trying to get rid of them." Another mechanism may be the increase in activities of paraoxonases by dietary antioxidants which can reduce oxidative stress.
Vitamin A (retinol), also synthesized by the body from
beta-carotene , protects dark green, yellow and orange vegetables and
fruits from solar radiation damage, and is thought to play a similar
role in the human body. Carrots , squash , broccoli , sweet potatoes ,
tomatoes (which gain their color from the compound lycopene ), kale ,
mangoes , oranges , seabuckthorn berries, wolfberries (goji), collards
, cantaloupe , peaches and apricots are particularly rich sources of
beta-carotene , the major provitamin A carotenoid .
VITAMIN COFACTORS AND MINERALS
Main article: carotenoid
Alpha-carotene - found in carrots, winter squash, tomatoes, green
beans, cilantro, Swiss chard
Natural phenols are a class of molecules found in abundance in plants.
Flavonoids , a subset of polyphenol antioxidants , are present in many berries , as well as in coffee and tea .
* Flavones :
* Flavonols :
* Flavanols and their polymers:
Catechin , gallocatechin and their corresponding gallate esters
* Stilbenoids :
PHENOLIC ACIDS AND THEIR ESTERS
Main article: polyphenol antioxidant
OTHER NONFLAVONOID PHENOLICS
* Curcumin - Curcumin has low bioavailability, because, much of it is excreted through glucuronidation . However, bioavailability is substantially enhanced by solubilization in a lipid (oil or lecithin), heat, addition of piperine , or through nanoparticularization. * Flavonolignans - e.g. silymarin - a mixture of flavonolignans extracted from milk thistle . * Xanthones - mangosteen is purported to contain a large variety of xanthones, but some of the xanthones like mangostin might be present only in the inedible shell . * Eugenol
OTHER POTENTIAL ORGANIC ANTIOXIDANTS
Capsaicin , the active component of chili peppers