Citrus Compound: Ready To Help Your Body!

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Citrus Compound: Ready To Help Your Body!

Apr 25, 2005 13:12 PDT

http://www.ars.usda.gov/is/AR/archive/feb05/citrus0205.htm

 

 

Citrus slices.

(K7226-29) These days, juicy, delicious oranges are practically

synonymous with vitamin C. But did you know that America's favorite

fruit also provides healthful natural compounds called limonoids? In

laboratory tests with animals and with human cells, citrus limonoids

have been shown to help fight cancers of the mouth, skin, lung, breast,

stomach, and colon.

 

 

Now, ARS scientists in northern California—led by chemist Gary D.

Manners of the Western Regional Research Center in Albany—have uncovered

new details about these compounds. Their research has demonstrated that

our bodies can readily access a limonoid called limonin, and all its

health-imparting properties, each time we bite into a citrus slice or

drink a glass of orange juice, for instance. This is the first time this

bioavailability has been shown in humans.

 

 

" Limonin is what remains after our bodies cleave a glucose, or sugar

molecule, from limonin's parent compound, limonin glucoside, " says

Manners. " Limonin glucoside is present in citrus and citrus juices in

about the same amount as vitamin C. "

 

 

Chemist Shin Hasegawa (retired)

prepares to analyze limonoids

in orange juice.

(K5919-1) Though the similar-sounding names of these limonoids may be

confusing, their positive impact on our health is becoming clearer with

every experiment.

 

 

In some individuals, limonin remains in the bloodstream for up to 24

hours—an impressive length of time—Manners and colleagues found. This

longevity, or persistence, may help explain some limonoids' ability to

fight cancer cells, which, if not continuously suppressed, may

proliferate.

 

 

The findings are good news for people who like oranges and the other

appetizing citrus fruits rich in limonoids. The world's citrus-juice

processors could also benefit; they could extract an estimated 300,000

pounds of these chemicals from peels, seeds, and other processing

leftovers each year.

 

 

Today, those leftovers, called citrus molasses, are sold as a low-cost

ingredient in cattle feed. But thanks to a patented, ARS-developed

process, these chemicals can be extracted from citrus molasses and used

to fortify foods or beverages.

 

Test Targets Limonin Glucoside

 

 

For the bioavailability experiment, 16 healthy men and women volunteers

downed a dose of pure limonin glucoside. The compound, a white,

tasteless, odorless powder, was dissolved in about 4 ounces of water.

Doses ranged from about one-eighth to one teaspoon. That's equal to the

amount in seven glasses of orange juice.

 

 

The participants gave blood samples before they drank the beverage and

3, 6, 12, and 24 hours afterwards. To avoid skewing test results, they

didn't eat or drink any citrus products for 3 days before and 3 days

after taking part in the study.

 

 

The scientists looked for traces of limonin—the limonin glucoside

byproduct or metabolite—in the volunteers' blood plasma. The laboratory

procedure that the researchers used, liquid chromatography-mass

spectrometry, can detect very small amounts of limonin.

 

 

Limonin showed up in the plasma of all volunteers except one. For most

volunteers, the concentration was highest within 6 hours after they

drank the special beverage. Five volunteers still had traces of limonin

after 24 hours. That's an indication of the compound's staying power, an

important consideration, especially if limonin glucoside were to be used

as a pharmaceutical, for example.

 

 

In contrast, some natural compounds are bioavailable for shorter periods

and have to be taken more than just once a day. An example: the

good-for-you phenols in green tea last only 4 to 6 hours.

 

 

In this study, Manners collaborated with Andrew P. Breksa III of the

Western Regional Research Center; Thomas S. Schooch, formerly of the

center; retired ARS chemist Shin Hasegawa, a pioneering investigator of

these citrus biochemicals; and Robert A. Jacob, formerly a chemist with

the ARS Western Human Nutrition Research Center in Davis, California,

and now retired. The group published their findings in a 2003 issue of

the Journal of Agricultural and Food Chemistry. The Florida Department

of Citrus helped fund the work.

 

Can Limonin Lower Cholesterol?

 

 

There's more to come from the California team. Manners and Breksa, along

with chemist Darshan S. Kelley and molecular biologist Susan J.

Zunino—both of the Davis nutrition center—are gearing up for a

first-of-its-kind study of the cholesterol-lowering effects of limonin.

 

 

In 2000, Manners, Hasegawa, and their Canadian co-authors reported that

limonin may be among the citrus-juice compounds that lower cholesterol.

In lab tests, they found that human liver cells produced less apo B—a

compound associated with higher cholesterol levels—when exposed to

limonin.

 

 

Preliminary results of the new cholesterol study are expected later this

year. This investigation may provide more details about the health

advantages of citrus and greater incentive for us to enjoy these sunny,

delectable fruits and juices even more often.—By Marcia Wood,

Agricultural Research Service Information Staff.

 

 

This research is part of Quality and Utilization of Agricultural

Products (#306) and Human Nutrition (#107), two ARS National Programs

described on the World Wide Web at www.nps.ars.usda.gov.

 

 

Gary D. Manners and Andrew P. Breksa III are in the USDA-ARS Processed

Foods Research Unit, Western Regional Research Center, 800 Buchanan St.,

Albany, CA 94710; phone (510) 559-5813, fax (510) 559-5849.

 

 

Darshan S. Kelley and Susan J. Zunino are with the USDA-ARS Western

Human Nutrition Research Center, One Shields Ave., Davis, CA 95616;

phone (530) 752-5138 [Kelley], (530) 752-5156 [Zunino], fax (530)

752-5271.

 

 

" Citrus Compound: Ready To Help Your Body! " was published in the

February 2005 issue of Agricultural Research magazine.

_________________

 

JoAnn Guest

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