With more than $200 million at stake, a federal jury in Philadelphia yesterday began to hear a bitter dispute between the makers of the artificial sweeteners Equal and Splenda.

Equal alleges that Splenda, which recently rocketed past its rival in sales, has misled consumers with its marketing slogan: "Made from sugar, so it tastes like sugar."

The slogan is so misleading, Equal's lawyer told jurors, that Splenda should be ordered to stop using it and pay Equal huge penalties.

"Consumers see this - 'Made from sugar' - and they think it's true," said Greg LoCascio, a lawyer for Equal. "Witness after witness and documents will show that [Splenda] knew consumers were confused about Splenda and they didn't do anything to stop it. . . . Instead, they enriched themselves by over a billion dollars."

Splenda contains sucralose, an artificial sweetener made through a process that begins with natural sugar but replaces three hydroxyl groupings in the sugar molecule with three chlorine atoms. The final product contains no natural sugar.

Yet "if you were to visit a Splenda factory," said Steven Zalesin, a lawyer for Splenda, during opening statements, "you would see trucks of sugar lining up. . . . Of all the artificial sweeteners, there's only one that starts with sugar and closely resembles sugar."

Splenda, introduced to the market in 2000, dramatically cut Equal's market share and now outsells it, 4-1, Zalesin said.

"This case is about accomplishing in the courtroom what the plaintiffs failed to accomplish in the marketplace," he said.

Equal is made by Merisant Co. Inc. of Chicago, which also makes NutraSweet. Splendra is made by McNeil Nutritionals L.L.C. of Fort Washington, a division of Johnson & Johnson.

Splenda is used in Coca-Cola, Pepsi, General Mills, and other mass-consumer products. Equal is generally distributed in blue packets at restaurants, grocery stores and clubs. It is made with aspartame, which is also used in 6,000 other consumer products worldwide.

Lawyers yesterday promised to show jurors internal marketing documents that they said would reveal the intense, behind-the-scenes efforts to pitch products to consumers.

In a pretrial ruling, U.S. District Judge Gene E.K. Pratter took note of the intense marketing efforts in the billion-dollar-a-year industry.

"The artificial-sweetener industry has long considered concerns from consumers regarding the taste and health safety of artificial sweeteners," she wrote. "In response to these concerns, manufacturers of artificial sweeteners have attempted to avoid using certain language, such as the term 'artificial,' that may convey negative taste or health-safety concerns."

The companies have spent tens of millions of dollars to promote these images. From 2000 to 2006, Splenda spent $235 million marketing its product, and Equal spent $108 million.

Equal seeks at least $208 million in damages, saying Splenda's claims have cost it $25 million in profits and unjustly earned $183 million for Splenda.

"You shouldn't be allowed to mislead consumers and get away with $200 million," LoCascio told jurors. "You shouldn't be allowed to mislead consumers with children that their product is natural and that, therefore, you should buy it."

Zalesin said Splenda did not try to mislead anyone. He noted, for example, that Splenda was marketed to diabetics - who clearly should not eat real sugar.

Splenda's marketing efforts to position itself as close to sugar as possible are no different from those of any other artificial sweetener, Zalesin said.

He mocked his opponents' brand name: "Equal? Equal to what? . . . The functional equivalent of sugar."

Besides damages, the makers of Equal seek a permanent injunction forbidding the makers of Splenda to use any false or misleading logo or statement. They also seek an order directing McNeil to institute a corrective advertising campaign, clarifying that Splenda is neither sugar nor natural.

The trial is expected to last three weeks.

Contact staff writer John Shiffman at 215-854-2658 or jshiffman@phillynews.com.