First, carrageenan is already known to America's Food and Drug Administration.

ECONOMIST: HIV microbicides

Carraguard is the proprietary name of a substance made from carrageenan, a carbohydrate gel derived from seaweeds that is widely used as a stabiliser in the food industry.

ECONOMIST: HIV microbicides

Carrageenan contains large negatively charged molecules called sulphated polysaccharides.

ECONOMIST: HIV microbicides