In botany, a fruit that has a stone containing a single seed is referred to as a drupe. A drupe is derived from one ovary of a flower. A skin or peel makes up the ovary’s outer wall, which contains a middle layer that is usually fleshy, but can be tough in the case of a coconut, for example.
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The stone-like inner layer of the drupe, referred to as the pit, usually contains a single seed. In some cases, the pit may contain more than one seed and usually only one seed matures properly. Examples of fruits that are classified as drupes include mangoes, coffee beans, dates, and olives.
Drupes are a rich source of antioxidants, molecules that target cell-damaging chemicals called free radicals. Unlike most molecules, which have even numbers of electrons, free radicals contain one or more unpaired or “free” electrons. Possessing an uneven number of electrons makes free radicals unsteady, highly reactive and unstable molecules that steal, remove or donate electrons from nearby intact molecules to balance their own electron number.
This stealing process, referred to as oxidation or reduction, respectively,, generates more free radicals, since the previously intact molecule is then left with one or more unpaired electrons. When free radicals oxidize key cellular components such as genetic material, proteins or cell membranes, their function is disrupted. When this “oxidative damage” accumulates, it can cause cell death and lead to organ damage, disease, and even death.
Free radicals are generated as a metabolic by-product of aerobic respiration when food is converted to energy or as a result of exercise. Exposure to sunlight, heavy metals, or the toxic chemicals present in tobacco smoke, or air pollution and heavy metals are other examples of external factors that lead to the formation of free radicals.
About antioxidants
Antioxidants inhibit this oxidative damage caused by free radicals by donating electrons, to free radicals to stabilize them, without becoming unstable and reactive themselves. Antioxidants are also involved in repairing DNA to maintain cellular health.
Hundreds of different types of substances serve as antioxidants, but the most well-known ones include vitamin C, vitamin E, carotenoids such as beta-carotene, and the minerals manganese and selenium. Other well-known examples are phenols, polyphenols, flavonoids, and phytoestrogens. Most antioxidants occur naturally, and eating food rich in these substances can prevent oxidative damage by defending the cellular environment.
Antioxidant properties of mangoes
The mango is rich in various types of polyphenol antioxidants including mangiferin, quercetin, anthocyanins, and benzoic acid. Mangiferin, in particular, has received much attention in the fields of nutrition and pharmaceutics, due to its anti-inflammatory properties and ability to fight chronic diseases such as heart disease and cancer.
The concentration of the different polyphenols varies depending on the part of the fruit, and mangiferin is highly concentrated in the stone, peel, stalk, leaves, kernel and bark. Extracts of this potent antioxidant have demonstrated promising health-related properties including hepatoprotective effects in liver damage, an iron-chelating ability that prevents the production of hydroxyl free radicals, and a promising preventative effect in colon cancer.
Antioxidant properties of coffee beans
Coffee beans possess antioxidant properties that protect against cancer, diabetes, liver disease, and the neurodegenerative disease Parkinson’s, as well as reducing overall mortality risk.
Green coffee beans contain high concentrations of the polyphenol 5-caffeoylquinic acid (5-CQA), a chlorogenic acid isomer that protects against DNA damage and decreases the amount of glucose that is released into the bloodstream following a meal. Chlorogenic acid is also well known for its ability to slow the oxidation of food products, which helps to extend the time that flavor and nutritional value are preserved for.
Antioxidant properties of dates
Polyphenols and flavonoids
The main phenolic acids found in date fruits are ferulic, vanillic, and syringic compounds. When dates are dried, heat and enzyme activity releases phenolic acids, which increases the concentration of phenolics in the fruit. The metal-chelating and free-radical scavenging properties of phenolics make them highly effective inhibitors of lipid peroxidation.
The flavonoids, found in dates include the flavanes, flavones, flavanones, flavonol glycosides, and anthocyanins. These flavonoids scavenge and inhibit superoxide anions, although the enzyme browning that occurs as the fruit ripens as well as during storage results in the loss of flavanes and anthocyanins.
Carotenoids
Examples of the carotenoids found in dates include lutein, β-carotene, and neoxanthin. The carotenoid content varies depending on the fruit variety as well as the process used to mature, dry and analyze the fruit. Carotenoid values vary due to differences in variety, maturation, drying, and analytical methods employed. Many studies have generated evidence supporting a cardioprotective role of carotenoids in preventing cardiac overload and early vascular alterations in atherosclerosis.
The carotenoid value is highest during the “khalal” stage, or second stage of ripening, when the date reaches its full size and changes color. During the fourth stage of ripening (called tamer), when dates are at their ripest, the carotenoid value starts to drop as a result of enzyme activity and the drying process.
Antioxidant properties of olives
The phenolic content of olive oil is known to play a role in preventing various forms of cancer, neurological disorders, and cardiovascular diseases. Virgin olive oils, which are key components of the Mediterranean diet, are rich in these natural antioxidants.
The phenolics found in virgin olive oils, including phenolic acids, flavonoids, glycosides, and secoiridoids, are key to preserving taste and flavor and contribute to oxidative stability and shelf life. The phenolic content also reduces oxidative damage and decreases the risk of chronic diseases such as atherosclerosis, cancer, and stroke, by protecting cell membranes from free radicals and decreasing levels of low-density lipoprotein.
References
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The Canadian Journal of Clinical Nutrition, Volume 6, Issue 2, June 2018
ISSN 1927-8942 (Print Edition), ISSN 1927-8950 (Online Edition)
The Canadian Journal of Clinical Nutrition is published by Global Science Heritage, (http://www.globalscienceheritage.org)
Registered publisher by the Library and Archives/Government of Canada, (www.collectionscanada.gc.ca)
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Further Reading