Listen to this Science Update to hear about how a male hummingbird makes sounds with his tail feathers to attract females.
In the beauty aisle of your local drugstore, you'll find a large assortment of skin products that promise to wipe out free radicals. But it turns out that sometimes free radicals can be beneficial. In this Science Update, you'll hear about efforts to boost those positive effects.
Wound-healing grapes. I'm Bob Hirshon and this is Science Update.
When most people eat grapes, the seeds go straight in the trash. But a new study has shown that grape seeds deserve a second look.
That's according to Chandan Sen, a physiologist at Ohio State University. He and his colleagues have found that an extract made from grape seeds can help wounds heal faster.
Sen says in the first step of wound healing, the body makes chemicals called free radicals. They sweep through the wound, killing bacteria and viruses.
The new story that we are now telling is that not only does a free radical detoxify, or disinfect a wound, but that it also supports the formation of new blood vessels, the formation of extra-cellular matrix, the replication, or multiplication of cells.
Sen says that grape seeds contain high amounts of a compound called proanthocyanidin. This compound turns into a free radical when it's applied directly to wounds, promoting new blood vessel and skin growth.
We worked with animals, where we caused a wound, and indeed, there was a massive acceleration of the healing process.
Sen says the next step would be to do more tests to determine whether it's safe and effective for humans. For the American Association for the Advancement of Science, I'm Bob Hirshon.
Making Sense of the Research
After hearing this report, your first question might be: How did these researchers ever figure out that an extract from grape seeds helps cuts heal? Did this discovery follow years of unsuccessful experiments with apple cores, orange rinds, and banana peels?
Actually, the study traces its roots back to tree bark, of all things. It turns out that treating wounds with bark from maritime pine trees is a popular folk remedy in France. When the researchers looked into the chemistry of this pine bark, they found it was rich in proanthocynanidins—the key chemicals described in this study. Then they looked through the chemical literature for a more convenient source of proanthocynanidins, found grape seeds, and were off and running.
This study is distinctive, in part, because it's the first time a natural substance has been shown to have such a positive impact on wound healing. It's also notable because it shows the positive side of free radicals. Free radicals are highly reactive chemicals that have been implicated in cancer, aging, and disease. Many people try to consume antioxidants (chemicals that react with and neutralize free radicals), either through foods or dietary supplements, to counteract their effects.
Here, we see that free radicals actually perform a positive function: they stimulate the growth of blood vessels and skin during wound healing, in addition to killing harmful viruses and bacteria. In fact, Sen and his colleagues have found that wounds don't heal as well if you squelch the process of forming free radicals. This doesn't diminish the negative impact free radicals may have elsewhere in the body, but it does show that they serve an important purpose in some situations, and shouldn't be eliminated completely.
Interestingly, Sen says that although proanthocyanidins turn into free radicals when applied to wounds, they act as antioxidants when they're eaten. That means that taking these chemicals orally probably won't help wounds heal; any drug made from these chemicals would have to be applied directly to the injury.
As for why these chemicals act differently in wounds than in the rest of the body, it seems that the presence of other free radicals in wounds actually changes the properties of the proanthocyanidins themselves. In other words, when they're surrounded by lots of free radicals, proanthocyanidins join 'em instead of trying to beat 'em. The advantage is that they last much longer than the free radicals made by the body, which explains why they're so effective.
Now try and answer these questions:
- What led the researchers to study grape seed extracts?
- What are proanthocyanidins? How do they react differently when applied to wounds, compared to when they're consumed in food?
- What are free radicals? What's distinctive about their role in wound healing?
- What are the advantages of using naturally occurring chemicals in medicine?
- Can you think of other substances that were once considered only destructive to health, but now are known to have some benefits?
World Wide Wounds is an online journal devoted to the subject of wound care and treatment.
How Antioxidants Work, by How Stuff Works, provides some more details about antioxidants and free radicals in the body.
It's a Jungle Out There!, from the New York Times Learning Network, is a lesson plan in which students learn about ethnobotany (the study of the uses of plants by different cultures).