Phytochemicals: The Ties That Bind

The Ties That Bind

This section is compiled by Frank M. Painter, D.C.
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From The July 2001 Issue of Nutrition Science News

By C. Leigh Broadhurst, Ph.D.

Analyzing the complex relationships of seemingly disparate botanicals to create health-enhancing effects on human metabolism

In today's marketplace, phytochemical is often used as a buzzword rather than in its true meaning—a classification system of botanical and chemical interactions. In broad terms, chemicals that plants synthesize during all or part of their normal life cycles are called phytochemicals. These processes involve plant meta-bolism and help explain, for example, how wood creates cellulose, sugar cane forms sucrose, and opium poppies produce morphine.

Within the context of nutrition and natural health, phytochemical refers only to plant chemicals that humans eat and use medicinally. The bioactive phytochemicals in these plants have significant positive effects on human metabolism. They also stimulate the senses, and are responsible for the color of blueberries, the aroma of cloves, the texture of mushrooms, and the taste of peppermint.

By understanding how specific phytochemicals form common threads between seemingly disparate botanical products, you'll be better equipped to use or recommend botanicals for dietary enhancement. A simplified phytochemical classification system is shown in Table 1.


The key phytochemicals in the European bilberry (Vaccinium myrtillus) and its American cousin blueberry (V. angustifolia, V. ashei, V. corymbosum) are anthocyanins. Bilberry has become popular for its ability to help correct vision disorders associated with retina degeneration, including macular degeneration, retinitis pigmentosa, poor night vision, and diabetic retinopathy. [1] It also improves or prevents glaucoma and cataracts. [2]

Anthocyanins are a subclass of flavonoids with an electric charge. Flavonoids have a basic structure, which is three linked six-membered rings—two benzene and one pyran. The electric charge of the anthocyanin causes the deep blue, orange, purple and red colors in flowers and fruits including apples, blackberries, cranberries, red and black currants, delphiniums, elderberries, grapes, peonies and petunias. [3] An anthocyanin consists of the three-ring anthocyanidin molecule proper. When sugar molecules bond in one to three locations, it is called an anthocyanoside.

When many anthocyanidins are linked, the polymer is called a proanthocyanidin, which is a condensed tannin. Purple grapes and red wines are the best-known dietary sources of proanthocyanidins, and cocoa powder is the richest food source. [4] Although there are only six anthocyanidins common in plants, the cyanoside and polymeric variations drive the total number of anthocyanins into the hundreds.

Anthocyanosides, found in fruits, do not contribute to the sweet taste or medicinal value, and are sometimes removed. The sugars linked to anthocyanosides have no medicinal value per se (this resides in the anthocyanin); therefore, the sugars are usually removed in the standardization process. For example, bilberry extract is standardized to either 25 or 36 percent anthocyanoside. An anthocyanoside's sugars make it more water soluble and less chemically reactive. This allows more anthocyanins to be extracted into juices and wines. Cyanidin and malvidin, the most widely consumed dietary anthocyanidins, are well absorbed in anthocyanoside forms. [5]

The hundreds of anthocyanin variations in grapes are largely responsible for wines' diverse tastes, bouquets, and colors. Several anthocyanins, such as peonidin cyanidin and delphinidin, have antioxidant and antiviral properties. Epidemiological research indicates that red wine in moderation reduces cardiovascular disease risk. [6] Elderberry and currant juices are used as health tonics for cold and flu treatment. [7] Because proanthocyanidins (found in currants, elderberries and grapes) are known to thin blood and strengthen capillaries, they aid in treating illnesses linked to poor circulation and blood clotting. [8]

Combining cranberry juice with a blueberry muffin and bilberry capsule is an excellent phytochemical breakfast combination. Cranberry (V. oxyooccos) proanthocyanidins are thought to help prevent and treat urinary tract infections. Amy Howell, research scientist at the University of New Jersey at Rutgers, in New Brunswick, N.J., found that cranberry proanthocyanidins prevent bacteria associated with urinary tract infections from attaching to the walls of the bladder and urethra. [9] Bacteria that can't adhere to the urinary tract are more easily excreted in urine. [10]

Cyclic Terpenoids

The most important cyclic terpenoids—sapogenins and phytosterols—have structures similar to plant and animal steroids, which have a basic structure of three linked six-membered rings and one five-membered ring. Steroids with hydroxyl groups have names that end in "ol," such as ethanol and menthol. Sapogenins and phytosterols differ only in the groups attached to the five-membered ring.

Steroids are waxy, soapy or greasy in texture, thus are more soluble in oil than water. The best-known animal sterol is cholesterol, which, despite its negative connotation, is essential for life and a critical component of cell membranes, organs, the brain and the nervous system. Just as cholesterol is the human precursor to all steroid hormones, such as cortisol, estrogen, progesterone, and testosterone, beta-sitosterol is the plant's precursor to growth and reproductive hormones.

Sapogenins that are stored in plants with sugars attached are called saponins. Some sapogenins, the nonsugar portion of a saponin, can mimic or regulate steroid hormones or hormone precursors. Yams (Dioscorea spp.), which contain variable amounts of the sapogenin diosgenin, can be converted into corticosteroids, dehydroepiandrosterone (DHEA), estrogen and progesterone in the laboratory, whereas the body cannot convert diosgenin into steroid hormones. Diosgenin has a weak estrogenic or progesteronic effect, which may account for its historical folk use by women. However, studies show its effects do not replicate those of sex hormones or any synthetic drugs used for hormone replacement. [11]

The yam North American herbalists use most often is D. villosa, which isn't as rich in diosgenin as are other species. Yam species used for food are lower in sapogenins than their wild progenitors (saponins are distasteful and can be toxic). Sapon, which means soap, refers to the saponins' tendency to foam in water. If you've prepared the grain quinoa, you may have noticed the instructions call for it to be rinsed before cooking.

Fenugreek (Trigonella foenum-graecum) is richer in diosgenin and other saponins than yams. Traditionally, fenugreek was prescribed to increase breast milk production and breast size. Although few studies support these indications, fenugreek saponins can lower cholesterol and blood lipids. [12]

The most celebrated saponins are ginsenosides from Korean ginseng (Panax ginseng). Although ginseng has been promoted as an aphrodisiac, ginsenosides resemble adrenal hormones more than sex hormones. Ginsenosides mildly stimulate the adrenal and pituitary glands, among other actions, which may account for ginseng's anti-fatigue and adaptogenic effects. [13] Another saponin-rich herb used throughout the Americas is sarsaparilla (Smilax officinalis), traditionally used to increase libido and flavor root beer.

Phytosterols can mimic or regulate human hormones or hormone precursors. They are thought to be the essential components of bee pollen, pumpkin seeds, pygeum (Pygeum africanum) and saw palmetto (Serenoa repens, S. serulatta)—all of which are used to treat enlarged prostates and prostatitis. [14] Phytosterol steroid mimicry also contributes to the anti-inflammatory effect of cold-pressed flaxseed and olive oils. [15]

Anthropologists and medical doctors who have studied the East African Masai tribe have shown that although 66 percent of their daily caloric intake comes from animal fat—meat, milk and yogurt—their serum cholesterol levels are low and cardiovascular disease is virtually nonexistent. Timothy Johns, Ph.D., of McGill University, Quebec, learned that the Masai's minor but judicious use of wild plant foods keeps their systems balanced. [16] They seem to add enough wild plants to milk- and meat-based soups to make them bitter and also drink herbal teas with meals, regularly chew tree barks and gums, use medicinal plants, and add herbs to their home-brewed honey beer. Johns found that 9 of 12 common Masai plant-derived food additives contain cholesterol-lowering phytosterols, saponins and/or phenolics.

Nuts are the richest source of phytosterols in Western diets, and numerous epidemiological studies show that diets rich in whole nuts are associated with a decreased incidence of cardiovascular disease. [17] In numerous clinical studies, subjects who ate 40 to 100 g/day of almonds, hazelnuts, macadamia nuts, pecans, pistachios and walnuts—nuts that often replaced 20 to 30 percent of their daily calories—experienced lowered serum triglycerides, total cholesterol and LDL cholesterol. [18]

Phytosterols are poorly absorbed and lower cholesterol by interfering with its absorption in the small intestine. Researchers have found in human tests that at least three grams of phytosterols daily show significant lipid-lowering effects. [19] David Jenkins, Ph.D., of the University of Toronto (who developed the glycemic index) and I speculate that the body is adept at manufacturing cholesterol because it is adapted to a wild, unprocessed hunter-gatherer diet, which is innately rich in fiber, phytosterols and saponins. These findings were presented at a meeting sponsored by the Heinz Institute of Nutrition at the University of Coleraine in Northern Ireland. This type of diet unavoidably depletes vital cholesterol at every meal, forcing the body to make more.

Cold-pressed unrefined vegetable oils such as flaxseed, hazelnut, olive, sesame, wheat germ and walnut are excellent sources of phytosterols, which also contribute greatly to the unique tastes, textures and aromas of these oils. Refining oil removes 20 to 60 percent of phytosterols, and hydrogenation removes an additional 20 to 40 percent. [20]

Algae and fungi also manufacture phytosterols. For example, ergosterol and other sterols from red yeast grown on rice have been shown to lower cholesterol. Asians using red rice yeast for health typically consume 14 to 55 g/day. [21] Anecdotal reports that mushrooms, seaweed, and spirulina lower cholesterol could be attributed to the fucosterol, sitosterol, ergosterol, and other sterols they contain.

Next time you read an article about a new or unfamiliar medicinal plant or phytochemical, try to tie a phytochemical thread from it to an herb or food plant with which you are already familiar. Don't ignore the scientific botanical classification as arcane or confusing, but use it to your advantage. This is the thought process that phytochemists use to avoid memorizing thousands of phytochemical names. Once established in your mind, these "threads" can aid your memory and give you quick access to basic information about a group of related plants.


Phytochemical Families & Their Sources

C. Leigh Broadhurst, Ph.D., heads 22nd Century Nutrition, a nutritional/scientific consulting firm, and is the author of Diabetes: Prevention and Cure (Kensington Publishing, 1999).


1. Morazzoni P, et al. Vaccinium myrtillus L. Fitoterapie 1996;66:3-29.

2. Camire ME. Bilberries and blueberries as functional foods and nutraceuticals. Functional foods: herbs, botanicals and teas. Mazza JG, Ooma BD. Lancaster, (PA): Technomic Publishing; 2000. p 289-319.

3. Mazza G, Minati E. Anthocyanins in fruits, vegetables, and grains, Boca Raton, (FL):CRC Press; 1993.

4. Hammerstone JF, et al. Procyanidin content in some commonly consumed foods. J Nutr 2000;130:2086S-92S.

5. Scalbert A, Williamson G. Dietary intake and bioavailability of polyphenols. J Nutr 2000;130:2073S-85S.

6. Soleas, GJ, Diamandis EP, et al. Resveratrol: a molecule whose time has come? And gone? Clin Biochem 1997;30:91-113.

7. Zakay-Rones Z, et al. Inhibition of several strains of influenza virus in vitro and reduction of symptoms by an elderberry extract (Sambucus nigra L.) during an outbreak of influenza B Panama. J Altern Compl Med 1995;1:361-5.

8. Arcagneli P. Pycnogenol in chronic venous insufficiency. Fitoterapie 2000;71:236-44.

9. Siciliano AA. Cranberry. Herbalgram 1996;38(Sep):51-3.

10. Avorn J, et al. Reduction of bacteriuria and pyuria after cranberry juice. JAMA 1994;271:751-4.

11. Araghiniknam M, et al. Antioxidant activity of dioscorea and dehydroepiandrosterone (DHEA) in older humans. Life Sci 1996;59:147-57.

12. Sharma RD, et al. Hypolipidaemic effect of fenugreek seeds: a chronic study in non-insulin dependent diabetic patients. Phytother Res 1996;10:332-4.

13. Wang LCH, Lee T. Effect of ginseng saponins on exercise performance in non-trained rats. Planta Medica 1998;64:130-3.

14. Buck AC. Phytotherapy for the prostate. Br J Urol 1996;78:325-6.

15. Visioli F, Galli C. Antiantherogenic components of olive oil. Curr Atheroscler Rep 2001;31:64-7.

16. Johns T. Phytochemicals as evolutionary mediators of human nutritional physiology. Int J Pharmacog 1996;34:327-34.

17. Sabate J, et al. Nut consumption and coronary heart disease risk. Handbook of Lipids in Human Nutrition. Boca Raton (FL): CRC Press; 1996. p 145-51.

18. Morgan WA, Clayshulte BJ. Pecans lower low-density lipoprotein cholesterol in people with normal lipid levels. J Am Diet Assoc 2000;100:312-8.

19. Jones PJ, Raeini-Sarjaz M. Plant sterols and their derivatives: the current spread of results. Nutr Rev 2001;59:21-4.

20. Farquar JW. Plant sterols: their biological effects in humans. Handbook of lipids in human nutrition. Boca Raton (FL): CRC Press; 1996. p 101-5 (See also appendix tables in this volume.)

21. Heber D, et al. Cholesterol-lowering effects of a proprietary Chinese red-yeast rice dietary supplement. Am J Clin Nutr 1999;69:231-6.

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