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Rice genetically modified to have high flavonoid content has a 22 per cent
higher antioxidant activity than untransformed rice, says a joint
German-Indian study, March 2007 by Stephen Daniells.

"The transgenic rice and its derived foods may serve as potential source
of antioxidant compounds and this helpful in promoting human health," wrote
lead author Ambavaram Reddy in the Elsevier journal Metabolic Engineering.

A number of genetically modified plants and crops are coming to light with
enhanced nutritional content considered to offer human health benefits,
including zeaxanthin to potato tubers, and the omega-3 fatty acid,
eicosapentaeoic acid (EPA), to soybeans, brassica, and stearidonic acid
(SDA) in canola crops.

However, no GM crops with potentially enhanced health benefits have been
approved for human consumption. Sonsumer acceptance, particularly in Europe
and most notably in the UK, continues to be one of the biggest challenges
for these crops.

Researchers from Hamburg University and the University of Hyderabad used the
"one gene-multiple metabolites" metabolic engineering concept to produce
strains of rice that overexpress the anthocyanidin synthase (ANS) enzyme,
obtained from a mutant strain of rice Nootripathu.

The ANS enzyme is part of the flavonoid biosynthetic pathway (the path for
producing flavonoids in the plant) and catalyses the formation of coloured
anthocyanidins from colourless leucoanthocyanidins, thereby serving as a
visible marker of the degree of anthocyanidin production.

Interest in flavonoids is growing rapidly and a mounting body of science,
including epidemiological, laboratory-based and randomised clinical trials,
continues to report the cancer-fighting potential of a number of different
flavonoids, such as isoflavones, anthocyanidins and flavonols.

Five different forms of transgenic rice were produced, and named 2T, 5T, 6T,
9T and 10TC. The latter (10TC) was found to contain the highest levels of
anthocyanins (2.52 micrograms per milligram) and the flavonol quercetin
(1.37 micrograms per milligram), and the lowest proanthocyanidins (0.09
micrograms per milligram), compared to the control rice (0.12, 0.55, and 0.4
micrograms per milligram, respectively).

This strain was also found to have the highest antioxidant activity with 98
per cent of radicals scavenged, compared to 77 per cent for the
untransformed plant, measured using the DPPH (1,1-diphenyl-2-picrylhydrazyl)
radical assay.

"Our study is a step towards the development of rice that is nutritionally
superior to the traditional and high yielding varieties in terms of
antioxidant potential," wrote the authors.

"This strategy can be extended to different food crops to promote
biofortification with natural products of nutritional value and to other
agriculturally important crops for enhanced resistance against biotic and
abiotic stresses," they concluded.

Rice is the primary food for more than three billion people around the
world.

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