Background
The authors state that high atmospheric CO2 concentrations may stimulate the secondary metabolism and antioxidant activity in plants, noting that Idso et al. (2000) - who evaluated the response of the tropical spider lily (Hymenocallis littoralis) to elevated levels of atmospheric CO2 over four growing seasons - found that "a 75% increase in the ambient CO2 concentration produced an 8% increase in pancratistatin, an 8% increase in trans-dihydronarciclasine, and a 28% increase in narciclasine that are efficient against lymphocytic leukemia and ovary sarcoma (Pettit et al., 1986)." These significant findings, together with the similar discoveries of others, prompted Ibrahim and Jaafar to likewise study the oil palm Elaeis guineensis (Jacq.) - the highest yielding vegetable oil crop in the world - which has gained wide recognition because of the health-promoting properties of some of its flavonoids and phenolics that the two scientists describe as "natural antioxidants that may reduce oxidative damage to the human body," citing the work of Mandel and Youdim (2004).

What was done
Over a period of 15 weeks, Ibrahim and Jaafar grew initially-five-month-old seedlings of three progenies of oil palm (deli AVROS, Deli Yangambi and Deli URT) within growth chambers maintained at atmospheric CO2 concentrations of either 400, 800 or 1200 ppm, during which time they measured a large number of important plant properties and processes.

What was learned
The two Malaysian researchers report that the production of total flavonoids and phenolics was highest under 1200 and lowest at 400 ppm CO2, and that "the antioxidant activity, as determined by the ferric reducing/antioxidant potential (FRAP) activity increased with increasing CO2 levels." In leaves, for example, they say that "total flavonoids was enhanced by 86% and 132%, respectively, in 800 and 1200 ppm compared to 400 ppm CO2," while total phenolics "increased by 52% to 91% under elevated CO2 compared to the ambient CO2 condition."

What it means
Ibrahim and Jaafar conclude that their results "suggest that enrichment with higher than ambient CO2 level is able to enhance the production of gallic acid and rutin in oil palm seedlings," which finding is important because these bioactive components, as they describe them, "act as free radical scavengers, and hence can reduce the possibilities of major diseases such as cancers of leukemia, breast, bone and lung," citing Kaufman et al. (1999) and Wink (1999).

References
Idso, S.B., Kimball, B.A., Pettit III, G.R., Garner, L.C., Pettit, G.R. and Backhaus, R.A. 2000. Effects of atmospheric CO2 enrichment on the growth and development of Hymenocallis littoralis (Amaryllidaceae) and the concentrations of several antineoplastic and antiviral constituents of its bulbs. American Journal of Botany 87: 769-773.

Kaufman, P.B., Cseke, L.J., Warber, S., Duke, J.A. and Brielmann, H.L. 1999. Natural Products from Plants. CRC Press, Boca Raton, Florida, USA.

Mandel, S. and Youdim, M.B. 2004. Catechin polyphenols: Neurodegeneration and neuroprotection in neurodegenerative diseases. Free Radical Biology and Medicine 37: 304-317.

Pettit, G.R., Gaddamidi, V., Herald, D.L., Singh, S.B., Cragg, G.M., Schmidt, J.M., Boettner, F.E., Williams, M. and Sagawa, Y. 1986. Antineoplastic agents, 120. Pancratium littorale. Journal of Natural Products 49: 995-1002.

Wink, M. 1999. Introduction: Biochemistry, Role and Biotechnology of Secondary Products. CRS Press, Boca Raton, Florida, USA, pp. 1-16.