“Trees mean water, water means bread, bread means life”: The Puranas
Plants, being the major source of medicine are fundamental to well being of mankind. Today approximately 80% of world’s population relies on traditional plant-based medicines for primary healthcare. The remaining 20% also depends on plant-based products for numerous health issues. Several key anti-cancer agents have been produced from natural sources; more than 60% of cancer drugs in market are based at least in part on natural products. Therefore, natural products should continue to be an important part of drug derivatives in the future.
What are Flavonoids
What do citrus fruits, grape seed extract, red wine, pine bark extract and onions have in common? They are all good sources of flavonoids, the plant pigments that helps fight a host of disorders, from cataracts and cancer to hay fever and menopausal hot flushes. Flavonoids form a large family of antioxidant compounds known as phytochemicals which form an integral part of a plant’s natural defense system.
Where are they found?
Flavonoids are ubiquitous components of herbivorous animals’ diet, because they are found in all plants. Owing to their polyphenolic nature, flavonoids often exhibit strong antioxidant properties, akin to ?-tocopherol, which they structurally resemble. Although animals do not directly synthesize flavonoids, their diets are full of flavonoids.
What do they do?
As antioxidants, some flavonoids such as Quercetin protect LDL cholesterol from oxidative damage. Others such as anthocyanidins from Bilberry, purple cabbage and grapes may help protect the lens of eyes from cataract. Animal research suggests that Naringenin found in grape fruit may have anti-cancerous properties. Soy isoflavones are also currently being studied to see if they help fight cancer. In addition to the antioxidant properties, flavonoids also exhibit inhibitory effect on a number of enzymes.
The ability to limit inflammation gives the flavonoids their disease fighting potential. They actively prevent the release of histamine in the body - this is the agent responsible for most allergy symptoms like congestion. Flavonoids also actively scavenge free radicals; they tend to boost immune system functioning and strengthen the blood vessels, thereby increasing the blood flow.
The cancer link
Flavonoids also exhibit potent anticancer effects, although the exact target of such inhibition has not been definitely established, given the recent evidence for a prominent role for reactive oxygen species (ROS) in carcinogenesis. It is tempting to speculate that flavonoids inhibit carcinogenesis due to ROS scavenging. However there have been a number of reports that directly contradict the potential role of flavonoids as antioxidants/anticancer agents.
Current case studies
In a small preliminary trial, Rutoside (500 mg twice daily) a derivative of flavonoid rutin combined with Vit C (500 mg) produced a marked improvement in 3 women with progressive pigmented purpura (PPP) a mild skin condition. Although not a serious medical condition, cosmetic concerns led persons with PPP to seek treatment with a variety of drugs. The Vit C-Rutoside combination represents a promising non-toxic alternative to these drug treatments, but larger, controlled trials are needed to confirm the preliminary results.
Grape seed extract and green tea are excellent sources of flavonoids and exert an antioxidant effect as well. It is usually best to combine with Vitamin C to enhance their protective properties. Quercetin should be taken 20 minutes before meals; other flavonoids can be taken at any time of the day.
Compound from hops used to make beer may help protect against cancer. Studies indicated that some of the flavonoids helped enhance the impact of class of enzyme called quinone reductase that can block cancer-causing substances that already have been activated. Flavonoids also inhibit an inflammation reaction in human skin tumor cells.
Epidemiological studies have shown a significant difference in cancer incidence among different ethnic groups, which is believed to be partly attributed to dietary habits. Soy isoflavones have been identified as dietary components having an important role in reducing the incidence of breast and prostate cancers. Genistein, the predominant isoflavone found in Soy has been shown to inhibit the carcinogenesis in animal models. Moreover, it has been shown that Genistein inhibits the activation of NF-Kappa B and Akt signalling pathways, both of which are known to maintain haemostatic balance between cell survival and apoptosis. Genistein as commonly known as phytoestrogen, which targets on estrogen and androgen mediated signalling pathways in the process of carcinogenesis. Furthermore, Genistein has been found to have anti oxidant property and shown to be a potent inhibitor of metastasis and angiogenesis. Taken together, both in vivo and in vitro studies have clearly shown that Genistein, one of the major Soy isoflavones is a promising reagent for cancer chemoprevention and/or treatment.
A preliminary study from the University of Arizona at Tucson, suggests that pine bark extract, which contains active ingredients similar to those of grape seed extract, may be as effective an anticoagulant and anticancer, so it may help to lower the risk of heart diseases and cancer.
Preliminary research suggests that green tea may also fight breast, stomach and skin cancer. Studies investigating how green tea might guard against cancer have pointed to the potency of its main antioxidant, a polyphenol dubbed EGCG (for epigallocatechin-gallate). Some scientists believe that EGCG may be one of the most effective anticancer compounds ever discovered, protecting cells from damage and strengthening the body’s own production of antioxidant enzymes.
An apple a day keeps oncologists away. Eating a lot of fruits and vegetables appears to confer some protection against many common cancers including malignancies of breast and lung. A new report provides especially good news that it is linked to lung cancer protection, strongly to diets high in flavonoid-rich apples. Quercetin is most common accounting for roughly 95% of all flavonoids consumers.
Previously published relevant literature for protection against some forms of cancer has shown many common foods have been considered as responsible agents and since then, much research activity has been done about their potential anticancer effect.
As a result these compounds have been shown to regulate proliferation and cell death pathways leading to cancer. Thus flavonoids such as the synthetic flavone, flavopiridol, soy isoflavonoid- Genistein, the tea-epigallocatechin fallate or the common dietary flavonol-quercetin are emerging as prospective anticancer drugs and some of them have already entered clinical trials.
In view of the therapeutic potential of flavonoids, many researchers have tried to elucidate possible structural activity relationships that might lead to new drug discovery. However, there is very little understanding about a possible relationship between flavonoid structure and anticancer activity. Besides their therapeutic potential since, lot of flavonoids are present in our diet a great understanding of their anticancer properties might also modify our dietary habits in order to prevent cancer.
References
Drug products and aromatic compounds obtained from plants; Irfan khan Volume 1, Chapter 2; page 7
Drug products and aromatic compounds obtained from plants; Special edition on cancer; Irfan khan Volume 5, Chapter 4; page 112-127
Drug products and aromatic compounds obtained from plants; Special edition on cancer; Irfan khan Volume 5, Chapter 2; page 7
Soy isoflavones and cancer prevention; pubmed; Sarkar FH, NY
Hops and its use in cancer, PubMed: Chan EK, NJ
in vitro and in vivo anticancer studies of dietetic products, Grant MD, QLD
The good, bad and ugly of flavonoids; a student assignment; Jeffery D. Kirsch, Feb 2001
The healing power of vitamins, minerals and herbs; RDI; 2000; p.288-289 & p.358-359
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