Researchers at the Agricultural Research Service, the chief scientific research agency of the US Department of Agriculture, are exploring the health benefits of citrus limonoids, compounds found in citrus fruits such as oranges.

In laboratory tests with animals and with human cells, citrus limonoids have already been shown to help fight cancers of the mouth, skin, lung, breast, stomach and colon. But now Agricultural Research Service scientists in northern California, led by chemist Gary Manners, are uncovering new details about these compounds.

Manners and co-researchers have demonstrated that each time we bite into a citrus slice or drink a glass of orange juice, our bodies can readily access a limonoid called limonin. The body derives limonin from a parent compound, limonin glucoside, which is present in citrus fruits and citrus juices in about the same amount as vitamin C, according to Manners.

In other early work, Manners and colleagues found that limonin may lower cholesterol. Now, the researchers are taking a closer look at limonin's potential cholesterol-lowering effects. Preliminary results of the cholesterol study are expected later this year.