Phytochemicals as Nutraceuticals

by Ben Best


  1. Introductory Remarks
  2. Terpenoids = Isoprenoids
    1. Carotenoid Terpenoids
      1. Lycopene
      2. Beta-Carotene
      3. Alpha-Carotene
      4. Lutein
      5. Zeaxanthin
      6. Astaxanthin
    2. Non-Carotenoid Terpeniods
      1. Perillyl Alcohol
      2. Saponins
      3. Terpeneol
      4. Terpene Limonoids
  3. Polyphenolics
    1. Flavonoid Polyphenolics
      1. Anthocyanins
      2. Catechins
      3. Isoflavones
      4. Hesperetin
      5. Naringin
      6. Rutin
      7. Quercetin
      8. Silymarin
      9. Tangeretin
      10. Tannins
      11. Punicalagin
    2. Phenolic Acids
      1. Ellagic Acid
      2. Chlorogenic Acid
      3. P-Coumaric Acid (Para-Coumeric Acid)
      4. Phytic Acid
      5. Ferulic Acid
      6. Vanillin
      7. Cinnamic Acid
      8. Hydroxycinnamic Acids
    3. Other Non-Flavonoid Polyphenolics
      1. Curcumin
      2. Resveratrol
      3. Pterstilbene
      4. Lignans
      5. Coumestans
  4. Glucosinolates
    1. Isothiocyanates
      1. Phenethyl Isothiocyanate
      2. Benzyl Isothiocyanate
      3. Sulforaphane
    2. Indoles
      1. Indole-3-Carbinol (I3C)
  5. Thiosulfonates
  6. Phytosterols
    1. Beta-Sitosterol
  7. Anthraquinones
    1. Senna
    2. Barbaloin
    3. Hypericin
  8. Capsaicin
  9. Piperine
  10. Chlorophyll
    1. Chlorophyllin
  11. Betaine
  12. Pectin
  13. Oxalic Acid
  14. Table of Dominant Phytochemical Pigments
  15. Other Sources of Information

I. Introductory Remarks

In this monograph I write about phytochemicals, ie, complex chemicals found in plants, notably in fruits and vegetables — with the focus on the phytochemicals rather than on their sources. This review is not comprehensive, it is simply a first attempt at classification of phytochemicals that have attracted my attention. Many phytochemicals have not been included.


Phytochemicals with antioxidant properties tend to be brightly colored because they contain chromophores, ie, a series of alternating single-bonded and double-bonded carbons. Isoprene is often the building block of such units. The darkest green vegetables contain the most chlorophyll, and vegetables with the most chlorophyll require the most antioxidants. Green will mask the other colors, when other-colored antioxidant phytochemicals are present.

Many phytochemicals have an anti-carcinogenic (anti-cancer) action by:

  1. slowing cell proliferation (division) by interfering with the cell cycle
  2. inducing apoptosis (cell suicide)
  3. inhibiting phase 1 enzymes (enzymes that convert harmless substances into carcinogens)
  4. inducing phase 2 enzymes (enzymes that can attach carcinogens to molecules that facilitate speedy excretion).

Phytochemicals are not classified as vitamins with official RDA values, but they can contribute greatly to health and well-being. We are adapted to a world that contains phytochemicals in our diet. The macula of the eye is adapted to concentrate the yellow caroteniods lutein and zeaxanthin to protect against harmful blue light.

Although the emphasis is on the positive effects of phytochemicals, note that very many can be toxic and harmful. Plants containing the most harmful phytochemicals are usually not treated as foods. Oxalic acid is included here because it is primarily harmful and is found in plant foods.

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II. Terpenoids = Isoprenoids

II-A. Carotenoid Terpenoids

Food Orange Carotenes
FoodBeta-Carotene *Alpha-Carotene *
Sweet potato (baked)9.50
Carrots, raw8.84.6
Pumpkin, canned6.94.8
Kale, cooked6.20
Spinach, raw5.60
* milligrams per 100 grams

Carotenoids make corn yellow, carrots orange and tomatos red. Carotenoids also give color to salmon, goldfish, flamingos and autumn leaves (when the green chlorophyll has gone, the carotenoids and phenols remain). Bell peppers of different colors offer a selection of carotenoids.

More than 600 carotenoids have been found in plants. About half of the roughly 50 carotenoids in the human diet are absorbed into the blood stream. Lycopene and beta-carotene each constitute about 30% of plasma carotenoids. Only alpha, beta and and a few other carotenes (not lycopene or lutein) can be converted to Vitamin A. Hypervitaminosis of Vitamin A cannot be caused by excessive alpha or beta carotene intake because the conversion and absorption rates are too slow. Both alpha-carotene and beta-carotene are protective against liver cancer and lung cancer in cell culture and animal studies.

Heating, chopping and/or crushing of vegetables frees-up carotenoids, especially beta-carotene & lycopene. Carotenoids are nearly insoluble in water and are best absorbed when associated with oils. In the blood stream carotenoids are transported in the most lipid-rich (LDL) cholesterol particles. Tissues with the most LDL receptors receive the most carotenoid.

II-A-1. Lycopene


II-A-2. Beta-Carotene


Although epidemiological studies have shown reduced lung cancer incidence among those with high plasma serum levels of beta-carotene, some large intervention studies showed an increased incidence of lung cancer among smokers taking beta-carotene supplements. (For more details, see General AntiOxidant Properties.)

II-A-3. Alpha-Carotene


II-A-4. Lutein


II-A-5. Zeaxanthin


II-A-6. Astaxanthin


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II-B. Non-Carotenoid Terpenoids

II-B-1. Perillyl Alcohol

II-B-2. Saponins

II-B-3. Terpeneol


II-B-4. Terpene Limonoids

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III. Polyphenolics


III-A. Flavonoid Polyphenolics

Flavonoids are flavone-like substances that are usually antioxidants and sometimes anti-inflammatory. Flavonoids scavenge free radicals by forming a stable radical that can react with another flavanoid radical to produce two non-radicals. The citrus flavanoids include rutin, hesperidin and naringin. Flavanoids and resveratrol are present in red wine, but are largely absent from white wine because white wine is made by pressing juice away from the solids, whereas red wine is made by fermenting the pulp along with the skin and seeds (although ultrafiltration is sometimes used to reduce astringency and bitterness). For detailed chemistry of the flavonoids, see Flavonoid AntiOxidants.

III-A-1. Anthocyanins

Anthocyanins are water-soluble glycosides and acyl-glycosides of anthocyanidins. Anthocyanins make roses red and violets blue. They make cherries & strawberries red and blueberries blue. Blueberries increase anthyocyanin content as they ripen. Anthocyanins have anti-inflammatory effects. Anthocyanins are easily damaged by heat (cooking). Up to 30 different anthocyanins have been found in wild blueberries and Concord grapes. Proanthocyanidins (colorless substances sometimes called "pycnogenols") are short-chained polymers of anthocyanidins that release anthocyanins with heat and/or acidic hydrolysis.


III-A-2. Catechins

Genistein: R1=OH, R2=H, R3=OH Daidzein: R1=H, R2=H, R3=OH Glycitein: R1=H, R2=OCH3, R3=OH

III-A-3. Isoflavones

III-A-4. Hesperetin

III-A-5. Naringin

III-A-6. Rutin


III-A-7. Quercetin

III-A-8. Silymarin

III-A-9. Tangeretin

III-A-10. Tannins

Tannin is a functional term rather than a distinct chemical group. Tannins have been used to tan and protect leather since the 18th century. Tannins are polyphenolics that make cranberries and pomegranates bitter. Tannins, along with Vitamin C, help build and strengthen collagen. Tannins prevent urinary tract infection by preventing bacteria from adhering to the walls. Combination of tannin plus anthocyanins (as in pomegranate juice) can break-down oxidized cholesterol in the bloodstream and in atherosclerotic plaques. Most of the active compounds in black tea are tannins which are 90% catechins. Epicatechin is the major component of natural tannin in grapes. The hydrolyzable tannins in aged wines come from the oak barrels, and are mainly composed of gallic acid and ellagic acid esters.


III-A-11. Punicalagin

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III-B. Phenolic Acids

Ellagic Acid
[Ellagic Acid]

Cranberry juice is rich in phenolic acids, which reduce adherence of bacteria to teeth and the cells lining the bladder — thereby reducing urinary tract infections and dental caries. Sweetening reduces the anti-adhesion properties of phenolic acids. Phenolic acids reduce oxidation of LDL cholesterol. Phenolic acids reduce the formation of cancer-promoting nitrosamines from dietary nitrates and nitrites. The most important phenolic compounds in grapes (red wine, grape juice, raisons) are proanthocyanidins, resveratrol and ellagic acid.

III-B-1. Ellagic Acid

III-B-2. Chlorogenic Acid

Caffeic Acid Ester
[Caffeic Acid Ester]

III-B-3. P-Coumaric Acid (Para-Coumeric Acid)

III-B-4. Phytic Acid

III-B-5. Ferulic Acid

III-B-6. Vanillin

Cinnamic Acid
[Cinnamic Acid]

III-B-7. Cinnamic Acid

Hydroxycinnamic Acids
[Hydroxycinnamic Acids]

III-B-8. Hydroxycinnamic Acids

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III-C. Other Non-Flavonoid Polyphenolics

III-C-1. Curcumin


Curcumin is a phytochemical in the spice tumeric which is used to make curry. (The spice "cumin" contains no curcumin, despite the similar name). Curcumin inhibits the gene that makes inflammatory COX-2 enzymes, preventing their production. (Celebrex simply inhibits COX-2 enzymes.) Curcumin is both strongly anti-inflammatory and strongly anti-oxidant. Curcumin inhibits release of the pro-inflammatory cytokine TNF-alpha. Curcumin is a more effective anti-clotting agent than aspirin, without the ulcer-inducing stomach irritation caused by aspirin.


III-C-2. Resveratrol

Resveratrol shows the strongest sirtuin-like deacetylase action of any known phytochemical. Sirtuins have been shown to extend the lifespan of yeast and fruit flies. Contrary to media representations, there are other sources of resveratrol besides alcoholic beverages (red wine) — such as purple grape juice.

III-C-3. Pterostilbene

III-C-4. Lignans

III-C-5. Coumestans

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IV. Glucosinolates

Glucosinolates convert to isothionates (contain sulfur) and indoles (contain no sulfur) when vegetables containing them are cut. They are high in cruciferous vegetables, particularly cauliflower & cabbage — and to a lesser extent in broccoli & brussel sprouts. They act against cancer by phase 2 enzyme induction. Broccoli and cabbage show the greatest protection against bladder cancer.

IV-A. Isothiocyanates

Isothiocyanates are responsible for the hotness of horseradish, radish and mustard. Isothiocyanates are (-N=C=S) compounds. Allyl isothiocyanate is also called mustard oil.

IV-A-1. Phenethyl Isothiocyanate


IV-A-2. Sulforaphane

IV-B. Indoles

IV-B-1. Indole-3-Carbinol (I3C)


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V. Thiosulfonates

Food Phytosterols
FoodBeta-Sitosterol *
Peanut butter135
Kidney beans91
* milligrams per 100 grams

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VI. Phytosterols

VI-A. Beta-Sitosterol

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VII. Anthraquinones

VII-A. Senna

VII-B. Barbaloin

VII-C. Hypericin

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VIII. Capsaicin

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IX. Piperine

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X. Chlorophyll

  1. X-A. Chlorophyllin

Chlorophyll Light-Absorption Spectrum
[Chlorophyll Light-Absorption Spectrum]

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XI. Betaine

XII. Pectin

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XIII. Oxalic Acid

See Calcium and Adequate Nutrition for more about kidney stones.

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XIV. Table of Dominant Phytochemical Pigments

The following table gives the phytochemical or phytochemical class which provides the predominant source of coloring for the specified fruits or vegetables





RED Anthocyanins Strawberries, Raspberries, Cherries, Cranberries, Pomegranates, Apples, Red Grapes
Lycopene Tomatoes, Pink Grapefruit, Watermelon
Betacyanins Beets
ORANGE Beta-carotene Carrots, Mangoes, Apricots, Cantelope, Pumpkin, Sweet Potatoes
Beta-cryptoxanthin Oranges, Tangerines
BLUE/PURPLE Anthocyanins Blueberries, Plums, Eggplant, Concord grapes
YELLOW Lutein, Zeaxantin Corn, Avocado
Curcumin Tumeric (Curry)
GREEN Chlorophyll Broccoli, Kale, Spinach, Cabbage, Asparagus, Green Tea
BLACK Thearubigens Black tea
Anthocyanins Blackberries

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XV. Other Sources of Information

For a good non-technical introduction to phytochemicals — with emphasis on plants of origin rather than chemistry — see THE COLOR CODE by James A. Joseph, (2002), and EAT YOUR COLORS by Marcia Zimmerman (2001).

My essay General Anti-Oxidant Actions contains much material which is relevant to understanding phytochemical action and effect.

For a review of the chemistry of phenolics found in grapes and wine, see ANNALS NEW YORK ACADEMY OF SCIENCES; Waterhouse,AL; 957:21-26 (2002).

A good review of the chemistry of polyphenols can be found in AMERICAN JOURNAL OF CLINICAL NUTRITION; Véronique Cheynier; 81(Suppl):223S-229S (2005)

List of phytochemicals

Linus Pauling Micronutrient Center

The World's Healthiest Foods

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