Getting Familiar With Flavonoids
Ever wonder what natural compounds account for the aroma, flavor and color of vegetables and fruits? The answer is flavonoids. Thousands of them.
Interest by the public in flavonoids has been increasing due to the growing reputation of food antioxidants that can have beneficial roles in disease prevention. The number of hits on Google for flavonoids is 2.52 million, and on PubMed, an online database just for medical research, there are over 34,000 original publications on flavonoids.
Flavonoids are a large family of phenolic compounds synthesized by plants as pigments that attract pollinators, repel pests and protect plant cells both from ultraviolet radiation and internal production of reactive oxygen species during photosynthesis.
As a group, flavonoids are the most associated phytochemical class with antioxidant values in plant foods.
Health scientists believe that people gain some of these same benefits by consuming flavonoid-rich plant foods, an area of active scientific study.
Current research trends on flavonoids
Scientists are keenly pursuing numerous potential health effects of flavonoids associated with fruit and vegetable-rich diets. Even in people without disease, benefits may occur for the cardiovascular system, brain, joints, skin, and urinary tract.
Many of the biological effects of flavonoids seem to come from their ability to modulate communication between cells, a new mechanism of flavonoid action in addition to the more traditionally accepted antioxidant activity.
Scientists are examining flavonoids as "biological response modifiers", a role where they may alter the body's responses to viruses, allergens, bacteria, carcinogens (cancer agents), inflammatory agents, and oxygen radicals.
Flavonoid intakes through the diet may help prevent cancer in humans.
Flavonoid consumption may lower risk of neurodegenerative diseases, as in Alzheimer's or Parkinson's disease.
While higher intakes of flavonoid-rich foods have been associated with reduced risk of some chronic diseases, it is not known whether isolated flavonoid supplements or extracts confer the same benefits as flavonoid-rich foods.
6 Major Classes of Dietary Flavonoids
Although flavonoids are related by a common chemical structure (called in chemistry, a "phenolic ring"), there are at least 4,000 variations in flavonoid structure and therefore more than 4,000 individual flavonoids in the plant kingdom. To manage such diversity, it is useful to group these compounds into 6 major classes, each having members with similar structure. The following groups have been devised by food chemists and give a place to start educating the public. The names of classes are similar because the chemical structures are closely related.
1. Anthocyanidins. Also called flavonals. Parent structure to anthocyanins found in red, blue, purple and black berries and grapes. Present in dark wines. Examples: cyanidin, delphinidin, petunidin, peonidin, malvidin, pelargonidin.
2. Flavanols. Found in black and green teas, berries, dark chocolate. Single structures ("monomers") are called catechins whereas multiple-unit structures ("polymers") are called proanthocyanidins, tannins, epigallocatechin, and theaflavins. May contain subgroups of ellagic or gallic acid. This class is also named flavan-3-ols.
3. Flavanones. Characteristic of citrus fruits (oranges, grapefruit, lemons), members of this group include naringenin, silybin and hesperidin.
4. Flavonols. Found in all plants with bright colors, such as berries, kale (dark green), broccoli and bell peppers, this group includes quercetin, kaempferol, myricetin, rutin and isorhamnetin.
5. Flavones. Represented by apigenin and luteolin, flavones are found in herbs (chamomille, parsley) and subterranean plants like celery and radishes.
6. Isoflavones. The signature group from soybeans and soy products (tofu, soy milk), isoflavone members include genistein and daidzein.
Less Antioxidant Activity Than We Hoped?
Due to their favorable chemical structure for serving as antioxidants, flavonoids are expected to be effective scavengers of free radicals in the human body, just as they are in the test tube ("in vitro").
However, even with very high flavonoid intake through the diet, blood and intracellular flavonoid concentrations in humans are around 100-1,000 times lower than concentrations of other known antioxidants, such as vitamin C, melatonin or glutathione. Part of this effect occurs because flavonoids do not stay in the blood or tissues, but are filtered by the kidneys into urine for excretion. Scientists would say from these circumstances that flavonoids are not very "bioavailable".
Also, it has been found that most circulating flavonoids are actually flavonoid substructures cleaved off from the parent molecule by stomach acids and metabolism. Naturally, some of these new, smaller flavonoid molecules have lower antioxidant activity than the parent.
For the reasons above, the relative contribution of dietary flavonoids to the body's antioxidant protection is less than predicted from their chemical structure and antioxidant activity in vitro.
Flavonoids Affect Communications Between Cells
Although initially thought that flavonoids would have antioxidant roles as their main biological function, new scientific evidence from cell culture research indicates that flavonoids can modify signaling activity between cells. Flavonoid concentrations needed to change cell signaling pathways are considerably lower than those required to serve antioxidant roles.
Changes in cell-to-cell signaling capability require enzymes known as kinases to sensitize target proteins ("receptors") at the receiving cell. Cell culture experiments indicate that flavonoids may affect chronic diseases by selectively inhibiting kinases.
This means that flavonoids may alter receptor sensitivity in certain diseases, such as in cancer by these candidate mechanisms:
1. Cancer cells depend on growth stimuli to enlarge and spread; flavonoids may inhibit cancer cells from communicating these signals to one another.
2. Cancer cells proliferate rapidly and lose their ability to undergo normal cell death signals ("apoptosis"; pronounced eh-poe-toe-sis); flavonoids may inhibit both the proliferation process and apoptosis.
3. Cancerous cells invade normal tissue aided by enzymes called matrix-metalloproteinases; flavonoids block the activities of these metal-containing enzymes.
4. Invasive tumors must also develop new blood vessels by a process known as angiogenesis to support their rapid growth; flavonoids inhibit angiogensis.
5. Tumor growth may depend on mechanisms of inflammation to grow, proliferate and resist apoptosis; flavonoids are well-established as anti-inflammatory agents.
Ongoing research will reveal additional characteristics of flavonoid biology in health and disease. It seems safe to conclude that the surest way consumers can gain the health rewards promised by flavonoid research is to consume plentiful plant foods containing them.
This should be an easy task as such foods are the most colorful and best-tasting fresh produce in the store -- Berries, red delicious apples, citrus fruits, black and green teas, red, orange, yellow and dark green vegetables, and even dark chocolate!
Reading
Flavonoids, Micronutrient Information Center, Linus Pauling Institute, Oregon State University, http://lpi.oregonstate.edu/infocenter/phytochemicals/flavonoids/
Database for the Flavonoid Content of Selected Foods, US Department of Agriculture, Nutrient Data Laboratory, http://www.nal.usda.gov/fnic/foodcomp/Data/Flav/flav.html
PubMed, online database of the US National Library of Medicine, http://pubmed.gov
Wikipedia on Flavonoids, http://en.wikipedia.org/wiki/Flavonoids
Ross JA, Kasum CM. Dietary flavonoids: bioavailability, metabolic effects and safety. Annu Rev Nutr. 2002; 22:19-34.
Joseph JA, Nadeau DA, Underwood A. The Color Code, Hyperion, 2002.
Related Tags: alzheimers, parkinsons disease, disease prevention, free radicals, flavinoids, help prevent cancer, food antioxidants, research on flavonoids, tumour growth, cancer cells, flavonoid-rich plant foods
Dr. Paul Gross is a scientist and expert on cardiovascular and brain physiology. A published researcher, Gross recently completed a book on the Chinese wolfberry and has begun another on antioxidant berries. Gross is founder of Berry Health Inc, a developer of nutritional, berry-based supplements. For more information, visit http://www.berrywiseonline.com Your Article Search Directory : Find in Articles
Recent articles in this category:
- Dental Insurance For Individual Can Be Of Help At Time
Dental problem may cost one a lot of money and pain. But, practicing a reasonable care could decreas - Personal Trainer For Perfect Health
There is a general misconception that need for a fitness trainer comes for novice or from those who - Varicose Veins - Causes, Symptoms, Treatment
The majority of people after thirty notice the changes that appear with the maturing. In this case t - Scenar Therapy - Self-treatment Or Healing Partnership
Do you want to learn about a device which will help you to ease your pain? If you get this kind of a - Scenar - 5 "no, Nos" Of Scenar
Are you fed up with the pain in your body? Various parts of our body seem to ache due to different r - Scenar Device - 5 Tips On Travelling With Your Scenar (skenar) Device
You might be aware of scenar which has become quite popular these days. This is actually the acronym - Scenar Therapy - How To Treat Your Pet With Scenar
There are many alternative methods of treatment that are being invented these days. Lots of people a - Your Options For The Treatment For Appendicitis
Appendicitis is considered to be a surgical illness. Due to its severe character, the treatment for - How To Choose The Right Copd Medication
Chronic obstructive pulmonary disease or COPD does not have any cure. But with the help of medicines - Septic Arthritis: Infectious Agents Penetrate Joints' Spaces
Another major type of arthritis is septic arthritis, which is also known in various terms like: pyog
Most viewed articles in this category:
- Drugs - the Last Alternative for Adhd in Kids
Anyone over the age of thirty who has grown up with ADHD understands that there was not much help av - Foods To Eat To Gain Weight
Malnutrition has the same degree of problem as obesity. There are people who are too skinny, they fi - Understanding Postpartum Clothing
The same way most pregnant women dream of the day when they will begin showing for wearing maternity - Kegel Exercising for Bladder Control and Enhanced Sexual Pleasure
Kegel exercises strengthen the muscles of the pelvic floor, thereby improving the urethra and/or rec - The Use Of Weight Loss Herbs
Nothing has garnered more attention in today's world than the success or failures of weight loss pro - A Simple Acid Relux Cure
Many people today are afflicted with heartburn. If they eat food that is too spicy, they get heartbu - Five Effective Household Back Pain Treatments
Back pain treatment comes in lots of forms, from exercise to pain mediction. Standard and most wides - Herbal Remedies - Can They Cure What Ails You?
You've probably heard about herbal remedies before and how they can treat a variety of health proble - Natural Relief for Tinnitus - What are your Choices
Natural Relief For Tinnitus - Alternative Options Did you know that there are an estimated 50 t - Birthing Around the World
Since ancestral times, different cultures showed off different customs and beliefs around the miracl