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Bioflavanoids
Flavonoids continue to attract wide attention as possible very useful agents for combating free radical pathologies, i.e. the pathological states associated with free radical overproduction (46). Experimental studies showed that
Flavonoids, particularly quercetin, the most abundant flavonoid in plants has cytoprotective potential as they are likely to be important in defending human DNA against oxidative attacks (47). Experimental studies have also shown that flavonoids have protective effect on the skin against carcinogenic agents (48).
Flavonoids relieves stress through its clear anxiolytic effect and thus stops the activation of the neuroendocrine stress axis which leads to increased level of oxygen and nitrous oxide free radicals and proinflammatory leukotrienes (49).
Flavonoids have also anti-inflammatory activity. It has been found to have in addition to the strong antioxidant activity, an eicosanoid enzyme inhibition property (50). Studies suggested that bioflavonoids may be a potential lead for a new type of anti-inflammatory agents having dual inhibitory activity of group 11 phospholipase A and
cyclooxygenase. It has been proved by animal experimental studies that it has both anti-inflammatory and analgesic property (51).
Flavonoids are natural products widely distributed in the vegetable kingdom and are capable of modulating the activity of enzymes that affect the behavior of many cell systems, suggesting that these compounds may possess significant antiallergic in addition to the anti-inflammatory activities (52). There have been numerous topical applications of plant extracts having flavonoids known as anti-inflammatory compounds. The anti-inflammatory activities, of some plants have been attributed at least in part to the inhibition of arachidonic acid cascade related enzymes by flavonoids (53). The effect of naturally occurring flavonoids on epidermal
cyclooxygenas/lipoxygenase was studied. The eicosanoid generated in the epidermis are believed to be involved in various biological activities of the skin. Experimental studies showed that flavonoids inhibit cyclooxygenase and lipoxygenase in various degrees, which explains their anti-inflammatory effect (54).
Flavonoids have been found to display significant antifungal activity (55). A group of polyphenolic
bioflavonoids, Proanthocyanidins, have been reported to exhibit a wide range of biological, pharmacological and chemoprotective properties against oxygen free radicals (56). Flavonoids works better when applied topically as they are poorly absorbed from the gut and are subject to degradation by intestinal microorganisms thus the amount remains biologically available may not be of sufficient concentration (57).
The clinical effect of bioflavonoids combined with ascorbic acid has been found to have beneficial effect in treating chronic progressive pigmented purpura as it increases capillary resistance and mediates potent antioxidative radical scavenging activities (58). Animal experimental studies showed that flavonoids have protective activity against skin vascular permeability (59).
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