Another reason to drink green tea.

"Every time you eat a sweet," Isao Kubo's grandmother used to say, "drink green tea." Though Kubo failed to heed her advice, he now acknowledges that he should have. An organic chemist, Kubo reported data last week demonstrating that flavor compounds in the Japanese brew can kill Streptococcus mutans - bacteria that help initiate dental caries.

The tea's cavity-fighting potential, confirmed roughly 10 years ago, first appeared to trace to water-soluble compounds, largely tannins, that cna halt S. mutan's production of glucans. These sticky materials bind acid-generating bacteria to teeth. However, a cup of tea did not appear to contain enough glucan inhibitors to account for its anticariogenic activity. So Kubo turned to the tea's hexanes - oily, floral-scented, water-insoluble compounds that give the drink its distinctive flavor.

At least nine of the 10 most abundant flavor compounds in green tea also inhibit glucan production, Kubo's team at the University of California, Berkeley, now reports. Moreover, when certain of these hexanes accompany one another, as they do in the tea, they can kill the microbes--and at far lower levels than required to shut down glucan production. For instance, even at 1,600 parts per million (ppm), caryophyllene alone exhibits no activity against the microbe. But when it accompanies 200 ppm of indole (half of that haxane's bacteria-inhibiting dose), a mere 6.25 ppm of caryophyllene kills S. mutans.

Nor are the hexanes' antimicrobial abilities restricted to S. mutans. Kubo found them active against all the strains he tested: two molds, three yeasts and eight bacteria, including some responsible for gastrointestinal disease and acne.

What if you don't like green tea? Its active hexanes also occur naturally in coriander, sage and thyme and as approved additives in ice creams, candy, chewing gum and baked goods. In the future, Kubo envisions green tea toothpastes and dental rinses.