The Potential Health Benefits of Purple Corn

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The Potential Health Benefits of Purple Corn

 

http://www.herbalgram.org/iherb/herbalgram/articleview.asp?a=2779

 

HerbalGram. 2005;65:46-49 © American Botanical Council

 

 

by Kenneth Jones

 

Purple corn is fast approaching classification as a functional food—

an integral component of the diet that provides energy and essential

nutrients. Researchers in the fields of food and nutrition are

intensely searching for functional foods in almost every corner of

the world and from a diversity of plants. Examples include purple

corn (Zea mays L., Poaceae), green tea (Camellia sinensis [L.]

Kuntze, Theaceae), soy isoflavones (Glycine max [L.] Merr.,

Fabaceae), various nuts, plus various other natural substances in

the human diet containing antioxidant and other substances with

alleged or proven potential disease-preventive properties.

 

Purple corn (frequently referred to as blue corn) is botanically the

same species as regular table corn. Yet by a twist of nature, this

corn produces kernels with one of the deepest shades of purple found

anywhere in the plant " kingdom. " Research has shown that purple corn

contains cell-protecting antioxidants with the ability to inhibit

carcinogen-induced tumors in rats. Many plant-derived substances are

believed to show these properties, but few have also demonstrated

anti-inflammatory capabilities and the potential to help prevent

obesity.

 

The kernels of purple corn (maiz morado in Spanish) have long been

used by the people of the Peruvian Andes to color foods and

beverages, a practice just beginning to become popularized in the

industrialized world. They also make a fermented/alcoholic drink

from the kernels which they call chicha morada.1

 

Rich in Anthocyanins

 

The source of this natural alternative to synthetic food dyes is the

largest group of natural, water-soluble pigments in the plant world,

known as " anthocyanins. " 2 (The word anthocyanin is derived from the

Greek terms, anthos, meaning flower, and kyanos, meaning blue.3)

Anthocyanins are responsible for the purple, violet, and red colors

attending many plants. Anthocyanins belong to an even larger class

of plant chemicals known as flavonoids and are found in diverse

plants, including many food plants.4

 

Researchers at the Horticultural Sciences Department of Texas A & M

University in College Station, Texas, recently determined that the

mean anthocyanin content of whole, fresh purple corn from Peru was

16.4 mg/g, which was much higher than fresh blueberries (1.3-3.8

mg/g). On a dry weight basis, the mean content of purple corn was

comparable to blueberries (17.7 and 9.2-24.0 mg/g, respectively).

The kernel pericarp held by far the greatest concentration of

anthocyanins, contributing 45% of the total content. More

intriguing, the in vitro antiradical capacity of purple corn extract

against the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical was greater

than that of blueberries (Vaccinium corymbosum L., Ericaceae), which

have shown higher antioxidant values than many other commercial food

plants.5

 

Powerful Antioxidant

 

Digging deeper, the most abundant anthocyanin found in purple corn,

called " C3G " (3-O-? -D-glucoside6,7), also known as cyanidin-3-O-?-

glucopyranoside,8 has been keeping researchers very busy lately. In

a number of tests designed to assess the potential health benefits

of this anthocyanin, one study after another has proven its

antioxidant strength. Like other anthocyanins, C3G is found in a

wide variety of food plants and is actually the most common

anthocyanin found in nature. C3G is the most abundant anthocyanin in

some foods, such as the juice of ruby oranges (Citrus sinensis [L.]

Osbeck " Blood orange, " Rutaceae)8 and blackberry (Rubus

allegheniensis [L.] Bailey, Rosaceae) extract.9 Red wine also

contains appreciable amounts,10,11 but other anthocyanins

predominate.12

 

C3G displays significant in vitro antioxidant activity. In one study

C3G came out on top when compared to 13 other anthocyanins in the

ORAC (oxygen radical absorbance capacity) assay, which tests for

antioxidant activity. The strength of C3G was 3.5 times that of

Trolox® (a synthetic and potent antioxidant analogue of vitamin

E).13 To date, the radical scavenging/antioxidant capacity of C3G

has been demonstrated in at least a dozen different assays.8,14-20

In one in vitro study, C3G was tested for the potential to prevent

damage caused by ultraviolet (UV) light. Its ability to inhibit the

oxidation of fat cells induced by UVB (280-315 nm) light was at

least 40 times that of vitamin E; however, vitamin E is a weak

inhibitor of UVB-induced lipid oxidation because it rapidly breaks

down under UV light.19 Oxidative stress and immune suppression

caused by UV light are well-known for their role in the induction of

skin cancers.20

 

Oxidative stress is described as a state in which there is an excess

of oxygen-based free radicals. To avoid the damage they can cause to

cells, the body produces antioxidants to inactivate these free

radicals. If they prove insufficient, however, the body suffers from

oxidation of lipids, proteins, and nucleotide bases. In models of

oxidative stress using oxidative injury to the liver, male rats fed

a diet containing 0.2% C3G (2 g/kg of feed) for 2 weeks beforehand

showed significantly less liver injury compared to the control

group.21 A similar study in rats fed C3G in liquid form (0.9

mmol/kg) also found significant hepatoprotective effects.22

 

Anti-inflammatory Capabilities

 

In a study on the anti-inflammatory potential of C3G, male rats

administered the anthocyanin orally in liquid form (0.9 mmol/kg)

prior to chemically-induced acute inflammation showed significantly

less inflammation and significantly attenuated levels of pro-

inflammatory cytokines (interleukin-6, interleukin-? , and tumor

necrosis factor-? , and inducible nitric oxide [iNOS] expression)

and nitric oxide (a free radical).23 Based on these results, it is

possible that this plant pigment may also suppress the inflammatory

response in diseases marked with inflammation.

 

Preventing Cancer

 

Could the anthocyanin pigment also help prevent some types of

cancer? That question was put to the test in rats first treated with

a carcinogen (1,2-dimethylhydrazine) and then fed a diet containing

a known environmental carcinogen (PhIP or 2-amino-1-methyl-6-

phenylimidazo[4,5-b]pyridine) that also targets the mammary gland,

prostate, and large intestine in rats and causes colorectal cancer.

Incidentally, the carcinogen used in the study, known as a

heterocyclic amine, is the most abundant of around 20 other types

found in cooked meats and fish. Both the early signs of colorectal

cancers and the numbers of malignant and benign tumors that formed

in the colons of rats that had the purple pigment in their diet (5%

of feed for 32 weeks; a nontoxic dose based on previous

carcinogenicity studies of PCC) were significantly reduced, and

there were no adverse effects. The authors of the study note that

extract or juices of plants that contain high amounts of

anthocyanins have previously been reported to inhibit mutagenesis

induced by heterocyclic amines.24

 

The oxidation of fats or lipids in blood serum contributes to the

condition known as atherosclerosis. When male rats were fed a diet

containing a high amount of C3G (0.2% of feed for 2 weeks) in place

of sucrose content in the control diet, their blood serum showed a

significantly lower level of oxidation along with a significant

decrease in the susceptibility of their serum lipids to undergo

oxidation, yet their body's natural antioxidants (serum levels of

vitamins C and E, glutathione, and uric acid) remained unaffected.

Another intriguing discovery in this study was that the rats with

C3G in their feed also showed significant decreases in levels of

total cholesterol—about 16% less.25

 

Anti-obesity Potential

 

What would happen if rats were fed C3G as part of a high-fat diet?

To find out, researchers in Japan compared the body weights of male

mice fed a high-fat (HF) diet with another group fed the same HF

diet but with the addition of purple corn color (PCC) which provided

C3G (0.2% or 2 g/kg of feed). Results were also compared to 2

control groups: one fed a normal diet and one fed a normal diet with

C3G. After 12 weeks, the results were obvious: mice in the PCC-HF

group showed significantly less signs of developing obesity, yet

exhibited no significant difference in food consumption compared to

the control groups with or without the PCC in their feed. When

related to the primary control group (no HF diet or PCC), the

adipose tissue weights of the PCC-HF group were not significantly

different. In addition, fatty tissue in HF-diet group was found to

be growing in size but showed no increase in the PCC-HF group. The

HF-diet group also developed a state of hyperglycemia along with an

over-production of insulin. Interestingly, this was not observed in

the PCC-HF group in which both pathologies were completely

normalized. In conclusion, the researchers stated that their tests

of PCC provide a nutritional and biochemical basis for the use of

the pigment or anthocyanins as a " functional food factor " —one that

may be beneficial for helping to prevent diabetes and obesity.26 It

now remains for future studies to determine the possible

contributing effects of other substances from purple corn which are

extracted along with PCC.

 

More recent efforts to determine the potential anti-obesity

mechanisms of purple corn pigment have focused on the effect of C3G

on fat cell dysfunction, fat cell-specific gene expression, and the

regulation of chemical messengers (adipocytokines) secreted by fat

cells, such as the fat-derived hormone adiponectin. After feeding

male mice a diet containing PCC to provide C3G (2 g/kg of feed for

12 weeks), gene expression levels of adiponectin in white fatty

tissue was upregulated 1.7-fold compared to the control group not

fed the food colorant.27 Plasma and gene expression levels of

adiponectin are decreased in obese humans and mice and in insulin

resistant states.27,28 When adiponectin was administered

intravenously to mice fed high-fat/sucrose diets, weight gain was

significantly inhibited. Adiponectin (i.v.) also lowered plasma

glucose levels in lean mice fed a high-fat meal.28

 

Rich in C3G (approximately 70 mg/g), about 50,000 kg of PCC is used

in Japan as a food color for confections and soft drinks annually.26

So far, PCC remains to be officially approved for use as a food

colorant by the U.S. Food and Drug Administration. However, approval

seems likely because " grape skin color " and " grape skin extract "

( " enocianini " or " enocyanin " )2 made from Concord grapes29 (Vitis

vinifera L., Vitaceae) are also rich in anthocyanins2 and both are

FDA-approved for use in beverages and non-beverage foods.29

 

 

 

Kenneth Jones is a medical writer specializing in the field of

medicinal plants. He is the co-author of Botanical Medicines: The

Desk References for Major Herbal Supplements by McKenna, Jones, and

Hughes (Haworth Herbal Press, 2002). He has no affiliation with any

commercial producers of purple corn or any of the other products

mentioned in this article.

 

 

 

References:

 

1. Brack-Egg A. Diccionario Enciclopédico de Plantas Útiles del

Perú. Cuzco, Peru: Imprenta del Centro Bartolomé de Las Casas;

1999:537-538.

 

2. Bridle P, Timberlake CF. Anthocyanins as natural food colours —

selected aspects. Food Chem. 1997;58(1-2):103-109.

 

3. Kong J, Chia L, Goh N, Chia T, Brouillard R. Analysis and

biological activities of anthocyanins. Phytochemistry. 2003;64:923-

933.

 

4. Mazza G, Miniati E. Anthocyanins in Fruits, Vegetables, and

Grains. Boca Raton, FL: CRC Press; 1993.

 

5. Cevallos-Casals BA, Cisneros-Zevallos L. Stoichiometric and

kinetic studies of phenolic antioxidants from Andean purple corn and

red-fleshed sweet potato. J Agric Food Chem. 2003;51(11):3313-3319.

 

6. de Pascual-Teresa S, Santos-Buelga C, Rivas-Gonzalo J C. LC-MS

analysis of anthocyanins from purple corn cob. J Sci Food Agric.

2002;82(9):1003-1006.

 

7. Nakatani N, Fukuda H, Fuwa H. Major anthocyanin of Bolivian

purple corn Zea mays. Agric Biol Chem. 1979;43(2):389-392.

 

8. Amorini AM, Fazzina G, Lazzarino G, et al. Activity and

mechanism of the antioxidant properties of cyanidin-3-O-b-

glucopyranoside. Free Radic Res. 2001;35:953-966.

 

9. Rossi A, Serraino I, Dugo P, et al. Protective effects of

anthocyanins from blackberry in a rat model of acute lung

inflammation. Free Radic Res. 2003;37(8):891-900.

 

10. Waterhouse AL. Wine phenolics. Ann N Y Acad Sci. 2002;957:21-36.

 

11. Burns J, Gardner PT, O'Neil J, et al. Relationship among

antioxidant activity, vasodilation capacity, and phenolic content of

red wines. J Agric Food Chem. 2000;48(2):220-230.

 

12. García-Beneytez E, Cabello F, Revilla E. Analysis of grape and

wine anthocyanins by HPLC-MS. J Agric Food Chem. 2003;51:5622-5629.

 

13. Acquaviva R, Russo A, Galvano F, et al. Cyanidin and cyanidin 3-

O-? -D-glucoside as DNA cleavage protectors and antioxidants. Cell

Biol Toxicol. 2003;19(4):243-252.

 

14. Wang H, Cao GH, Prior RL. Oxygen radical absorbing capacity of

anthocyanins. J Agric Food Chem. 1997;45(2):304-309.

 

15.Espin JC, Soler-Rivas C, Wichers HJ, Garcia-Viguera C.

Anthocyanin-based natural colorants: A new source of antiradical

activity for foodstuff. J Agric Food Chem. 2000;48(5):1588-1592.

 

16. Kähkönen MP, Heinonen M. Antioxidant activity of anthocyanins

and their aglycons. J Agric Food Chem. 2003;51(3):628-633.

 

17. Stintzing FC, Stintzing AS, Carle R, Frei B, Wrolstad RE. Color

and antioxidant properties of cyanidin-based anthocyanin pigments. J

Agric Food Chem. 2002;50(21):6172-6181.

 

18. Tsuda T, Watanabe M, Ohshima K, et al. Antioxidative activity

of the anthocyanin pigments cyanidin 3-O-? -D-glucoside and

cyanidin. J Agric Food Chem. 1994;42(11):2407-2410.

 

19. Tsuda T, Shiga K, Ohshima K, Kawakishi S, Osawa T. Inhibition

of peroxidation and the active oxygen radical scavenging effect of

anthocyanin pigments isolated from Phaseolus vulgaris L. Biochem

Pharmacol. 1996;52(7):1033-1039.

 

20. Morazzoni P, Bombardelli E. Vaccinium myrtillus L. Fitoterapia.

1996;67:3-29.

 

21. Tsuda T, Horio F, Kitoh J, Osawa T. Protective effects of

dietary cyanidin 3-O-b-D-glucoside on ischemia-reperfusion injury in

rats. Arch Biochem Biophys. 1999;368(2):361-366.

 

22. Tsuda T, Horio F, Kato Y, Osawa T. Cyanidin 3-O-b-D-glucoside

attenuates the hepatic ischemia-reperfusion injury through a

decrease in the neutrophil chemoattractant production in rats. J

Nutr Sci Vitaminol. 2002;48(2):134-141.

 

23. Tsuda T, Horio F, Osawa T. Cyanidin 3-O-b-D-glucoside

suppresses nitric oxide production during zymosan treatment in rats.

J Nutr Sci Vitaminol. 2002;48(4):305-310.

 

24. Hagiwara A, Miyashita K, Nakanishi T, Sano M, Tamano S, Kadota

T, Koda T, Nakamura M, Imaida K, Ito N, Shirai T. Pronounced

inhibition by a natural anthocyanin, purple corn color, of 2-amino-1-

methyl-6-phenylimidazol[4,5-b]pyridine (PhIP)-associated colorectal

carcinogenesis in male F344 rats pretreated with 1,2-

dimethylhydrazine. Cancer Lett. 2001;171:17-25.

 

25. Tsuda T, Horio F, Osawa T. Dietary cyanidin 3-O-? -D-glucoside

increases ex vivo oxidation resistance of serum in rats. Lipids.

1998;33(6):583-588.

 

26. Tsuda T, Horio F, Uchida K, Aoki H, Osawa T. Dietary cyanidin 3-

O-? -D-glucoside-rich purple corn color prevents obesity and

ameliorates hyperglycemia in mice. J Nutr. 2003;133(7):2125-2130.

 

27. Tsuda T, Ueno Y, Aoki H, et al. Anthocyanin enhances

adipocytokine secretion and adipocyte-specific gene expression in

isolated rat adipocytes. Biochem Biophys Res Commun. 2004;316:149-

157.

 

28. Fruebis J, Tsao TS, Javorschi S, Ebbets-Reed D, Erickson MR,

Yen FT, Bihain BE, Lodish HF. Proteolytic cleavage product of 30-kDa

adipocyte complement-related protein increases fatty acid oxidation

in muscle and causes weight loss in mice. Proc Natl Acad Sci USA.

2001;98:2005-2010.

 

29. FDA, Dept. of Health and Human Services. Code of Federal

Regulations. Part 73. Listing of Color Additives Exempt from

Certification. Sec. 73.169. Sec. 73.170. April 1, 2003. Available

at: http://www.access.gpo.gov/cgi-bin/cfrassemble.cgi?title=200321.