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Walnut mystery is finally cracked

Mary Grace has developed a compulsive habit over the past 14 months. But she’s not worried about it.

“I love walnuts,” said the senior researcher for N.C. State’s Plants for Human Health Institute in Kannapolis. “I can’t prevent myself from eating them while we’re working on this.”

Chock full of proteins, healthy fats and essential vitamins and minerals, walnuts are a well-known super food. What hasn’t been known is an effective way to explore some of their health-promoting compounds and show how they interact, which could pave the way for even greater health benefits.

Recent research by N.C. State is changing that. A team of scientists led by Grace has found a unique method for identifying and isolating these compounds – known as phytochemicals – after years of struggles within the research community. Now, researchers can gather phytochemical samples large enough to conduct animal and clinical trials that can verify these healthful properties.

The N.C. State study was published this fall in the scientific journal Food Chemistry.

Technology and technique

“Through the process of isolation, we identified many compounds,” Grace said. “Two of them were new.” (Praecoxin A-methyl ester, which was abundant in a form of walnut extract, and Glansreginin A-nbutyl ester, which was isolated as a minor compound from that same extract). “This is different from other methods of isolation. It’s very efficient in isolating these compounds.”

The walnut’s hard exterior can pose a challenge for research purposes. “They’re not an easy tissue to extract from,” said Mary Ann Lila, co-author of the study and director of the Plants for Human Health Institute. “It’s not like squeezing a berry and getting the juice. It’s a walnut.”

Some rare instruments used in the PHHI lab are helpful there. That technology utilizes a liquid chromatography technique called countercurrent chromatography.

In liquid chromatography, a compound is separated into its individual parts based on the interactions of samples of the mobile and stationary parts. Countercurrent chromatography is a technique that uses two liquid components that can’t mix when added together – like water and suntan lotion. One liquid is stationary; the other is mobile. The liquid portion is held in place by the gravity of centrifugal force.

This process prevents the compounds from being diluted during extraction, which has historically prevented them from being collected in adequate amounts.

“Countercurrent chromatography allows us to do large volumes, cleanly, of separation of these compounds,” Lila says. “That’s a big advantage, because the whole point of our doing this work was to make ourselves a resource for all of the researchers who are doing walnut research – not just in the United States, but in the world. Many labs that have done work they don’t have enough isolated compound to do an animal study, much less a clinical study.”

The separated extraction is then examined by another lab instrument – high-performance liquid chromatography – which identifies and quantifies the compounds within the walnut extraction. The extraction is mixed in some basic solvent (sometimes just water) for testing purposes, and placed in vials or tubes for testing with instruments.

What’s possible with proof

Future implications of this study are numerous, given the walnut’s potential health benefits in so many realms. Grace mentions the lab’s work with the J. Brandon White Cancer Research Group at California’s San Jose State University.

“Research is also going on with walnuts’ effectiveness against cardiovascular disease and aging issues,” she said, and as an antidiabetic that can reduce glucose levels and increase insulin sensitivity. “These undiscovered natural components in walnuts can contribute to human health protection in many ways.”

Lila said that validating or proving walnuts’ healthful properties is essential for this research to deliver the maximum benefit.

“The important thing is that until you know what’s doing something, until you know what’s anti-carcinogenic, until you know what’s lowering blood glucose levels, you won’t get buy-in from the medical community. You just won’t. It’ll seem like folklore if you don’t.

“Doctors won’t buy into it, they won’t give nutritional advice, unless they can figure out the why.” Armed with this knowledge, “you can start to grasp what kind of dosage a person needs in their foods in order to protect themselves.

“That’s the real value: getting at what these compounds are. Even if you do eat them altogether in a walnut, you can have a better grasp of what’s protecting your health.”

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