Antidiabetic Potential of Nettles and Walnut Leaves


Juglans regia: Nut and leaves. Photo by Sten Porse.

According to a recent study from Iran, stinging nettle leaves (Urtica dioica) and walnut leaves (Juglans regia) may have potential in antidiabetic therapy. Diabetes affects over 100 million people worldwide. This disease condition causes blood glucose (sugar) levels to rise, because people with diabetes either do not make enough insulin or are unable to use insulin properly. Normally, Insulin helps glucose from blood enter muscle, brain and liver cells where it is used to generate energy. When glucose levels build up in blood, these cells become starved for energy. Over time, high blood glucose levels also damage the eyes, kidneys, nerves and heart.

Carbohydrates are a major component of our daily diet. They are broken down in the gut into simple compounds called monosaccharides by the enzyme alpha-amylase before they are absorbed into the blood. Blocking the activity of alpha-amylase prevents carbohydrate digestion and has been shown to reduce blood glucose levels. In fact, ‘alpha-amylase inhibitors’ have been developed to treat diabetes in this way. While currently available alpha-amylase inhibitors do provide short-term diabetes control, they also cause serious side effects. This is why scientists are studying natural extracts from over 400 traditional medicinal plants with alpha-amylase blocking activity for their exciting potential as effective, and likely safer, antidiabetic therapies.

Urtica dioica Flowers (female) can be green and white. Photo by Frank Vincentz.

In this study from Hormozgan University of Medical Sciences in Bandar Abbas in Iran, researchers examined the effects of leaf extracts from Urtica dioica and Juglans regia on alpha-amylase activity. U. dioica, known as the common nettle or stinging nettle, has a long history as a medicine and as a source of both food and fiber. J. regia – known as the English walnut, common walnut or California walnut – is a common food. Walnut leaves also have a long history of medicinal use. Extracts of both plants strongly blocked alpha-amylase activity. Nettle caused a 60% inhibition of the enzyme with 2 mg/ml of the extract, and walnut leaf extract required only 0.4 mg/ml for the same inhibition. This effect increased with time and dose of extract. In conclusion, the medicinal plants Urtica dioica and Juglans regia may have potential as antidiabetic therapies.   Technical Summary

Aqueous extracts of U. dioica and J. regia showed time- and concentration- dependent inhibition of alpha-amylase. The extracts consisted of 100 g of powdered dried leaves in 100 ml of water, freeze dried to powder. The extracts demonstrated 60% inhibition of alpha amylase activity with 0.4 mg/ml of nettle leaf extract and 2.0 mg/ml of walnut leaf extract. Inhibition increased for both extracts from 40% at 5 minutes and 60% at 30 minutes. “The results showed that the type of inhibition was competitive in which enzyme-inhibitor complex could form.” This research follows the discovery that walnut leaf reduced blood sugar in diabetic rats and other supportive studies. See the full article [LINK] for all the details.

The authors note:

 For the first time, the mechanism of inhibition for U. dioica and J. regi extract was investigated and the results showed that the extracts inhibited PPA through competitive mechanism… The data from this study could provide a basis for further investigations where the active component that results in PPA (alpha-amylase) inhibition could be isolated.

We hasten to note that it isn’t always necessary or desirable to isolate “the active component.” That’s drug company talk. If a simple water extract of these plants can be effective, why must we make a powerful, high cost pill out of “the active component?”   Rahimzadeh M, Jahanshahi S, Moein S, Moein MR. Evaluation of alpha- amylase inhibition by Urtica dioica and Juglans regia extracts. Iran J Basic Med Sci 2014; 17:465-469.

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