The tip of the sweet potato is about 10 to 15 cm long from the sweet potato stem, and contains a large amount of protein, fibre, potassium, and vitamins.
The national agency measured the anti-inflammatory, anti-diabetic effects in six varieties of the local sweet potato varieties.
Of which, the white-fleshed variety Hayanmi showed the best findings for anti-inflammatory benefits.
The sweet potato tip extract of Hayanmi could suppress inflammation by reducing the amount of nitric oxide – which is produced during the inflammatory reactions – by up to 76.4 per cent as seen in mouse macrophages.
Macrophages are cells involved in destroying bacteria. The cells were treated with lipopolysaccharide to induce inflammation in the mouse prior to the test.
In terms of its anti-diabetic effect, it was found that the extract could inhibit the activity of alpha-glucosidase – an enzyme which breaks down starch into simple sugars and can induce a rapid increase in blood sugar as a result.
Of which, Hayanmi, together with the orange-fleshed varieties Juwhangmi and Gogeonmi were found to have the best anti-diabetic effect.
Findings from the cell study showed that the best result was reducing alpha-glucosidase enzymatic activity by up to 81 per cent.
At the moment, alpha-glucosidase inhibitors medications such as acarbose and miglitol are used to control blood sugar in diabetics.
The agency said it had been trying to develop different varieties of sweet potatoes where various parts could be used for improving health.
"We are working hard to develop varieties that can utilise various sweet potato parts to improve public health and farm income,” said Yeon-Sang Song, director of the Bioenergy Crop Research Center of the National Institute of Crop Science at RDA.
An existing study from China has showed that sweet potato supplementation could significantly reduce obesity caused by a high-fat diet.
Bioactives content
Sweet potatoes are also known to contain antioxidants such as beta-carotene, as well as anthocyanin and lutein beneficial to the eye.
According to another study published by the RDA last year, there is no one variety of sweet potato which contains a high concentration of all bioactives such as lutein and anthocyanins.
For example, while the Juwhangmi variety has the highest amount of lutein at 47mg/100g, it is the Hayanmi variety which has the highest amount of beta-carotene at 183.4mg/100g.
On the other hand, the Hogammi variety has the highest amount of anthocyanin at 378.5mg/100g, while Pungwonmi is highest in total polyphenol content at 7440mg/100g.
Antioxidant activities were the highest in the Gogeonmi and Healthymi varities.
Based on the results, the researchers identified Juhwangmi, Hayanmi, and Gogeonmi as being varieties suitable for tip cultivation.
