Background
The authors write that "free radicals and single oxygen are recognized as major factors causing various chronic diseases such as cancer, diabetes, etc.," and as a result, they note that "the health maintenance function of antioxidant components in various foods has received much attention," citing Byers and Guerrero (1995) and Namiki (1990). In this regard, they further indicate that "phenolic acids and flavonoids are antioxidants with health benefits such as anti-inflammatory and anti-tumor effects (Heijnen et al., 2001; Chun et al., 2003; Harborne and Williams, 2000; Chen, 2004)," specifically stating that "Sung-jin et al. (2008) showed that some flavonoid components in green tea are effective in inhibiting cancer or induce mechanisms that may kill cancer cells and inhibit tumor invasion."

What was done
Working with Malaysian young ginger (Zingiber officinale) -- one of the medicinal/food plants that have been used by Polynesians for over 2,000 years for treating cancer, diabetes, high blood pressure, and many other illnesses -- the Malaysian researchers grew two varieties of the plant (Halia Bentong and Halia Bara) from rhizomes planted in a drip-irrigated 1:1 mixture of burnt rice husk and coco peat in polyethylene bags placed within controlled-environment chambers that were maintained at atmospheric CO2 concentrations of either 400 or 800 ppm for a period of 16 weeks, after which the plants were harvested and their leaves and rhizomes analyzed for a wide variety of phenolics and flavonoids, along with their free radical scavenging power, which is a measure of their ability to prevent dangerous reactive oxygen species from attacking various parts of the body and causing a large number of potentially life-threatening maladies.

What was learned
Ghasemzadeh et al. report that, on average, "flavonoid compounds increased 44.9% in leaves and 86.3% in rhizomes of Halia Bentong and 50.1% in leaves and 79% in rhizomes of Halia Bara when exposed to elevated carbon dioxide conditions," while phenolic compounds increased even more: by 79.4% in leaves and 107.6% in rhizomes of Halia Bentong and 112.2% in leaves and 109.2% in rhizomes of Halia Bara under the same conditions. In addition, they determined that when the CO2 concentration was increased from 400 to 800 ppm, the free radical scavenging power increased by 30.0% in Halia Bentong and 21.4% in Halia Bara. And they again report that "the rhizomes exhibited more enhanced free radical scavenging power, with 44.9% in Halia Bentong and 46.2% in Halia Bara."

What it means
Quoting the three scientists, "these results indicate that the yield and pharmaceutical quality of Malaysian young ginger varieties can be enhanced by controlled environment production and CO2 enrichment." These same benefits will also accrue without any effort on man's part as the air's CO2 content continues to rise. And it should be noted that this beneficial consequence of atmospheric CO2 enrichment has been documented in a variety of medicinal/food plants, as may be seen by perusing the materials we have archived under the headings of Health Effects (CO2 -- Health-Promoting Substances: Common Food Plants) and Health Effects (CO2 -- Health-Promoting Substances: Medicinal Plants).

References
Byers, T. and Guerrero, N. 1995. Epidemilogic evidence for vitamin C and vitamin E in cancer prevention. American Journal of Clinical Nutrition 62: 1385-1392.

Chen, G. 2004. Effect of low fat and/or high fruit and vegetable diets on plasma level of 8-isoprostane-F2alpha in nutrition and breast health study. Nutrition and Cancer 50: 155-160.

Chun, O.K., Kim, D.O. and Lee, C.Y. 2003. Superoxide radical scavenging activity of the major polyphenols in fresh plums. Journal of Agriculture and Food Chemistry 51: 8067-8072.

Harborne, J.B. and Williams, C.A. 2000. Advances in flavonoid research science. Phytochemistry 55: 481-504.

Heijnen, C.G., Haenen, G.R., Vanacker, F.A., Vijgh, W.J. and Bast, A. 2001. Flavonoids as peroxynitrite scavengers: the role of the hydroxyl groups. Toxicology in Vitro 15: 3-6.

Namiki, M. 1990. Antioxidant/antimutagens in food. Critical Reviews in Food Science and Nutrition 29: 273-300.

Sung-Jin, P., Hoon, M., Young-Youn, K., Jun-Young, P., Jun-Woo, P., Myung-Jin, K. and Soon-Min, H. 2008. Anticancer effects of genistein, green tea catechins, and cordycepin on oral squamous cell carcinoma. Journal of Korean Oral and Maxillofacial Surgery 34: 1-10.