Alpha-glucosidase inhibitory effect and antioxidant properties of different extracts from Lycium barbarum L.

Abstract

Fruits of the plant Lycium barbarum L. (Goji berry) fruit have been widely used around the world for their medicinal purposes and as a functional food for more than 4500 years. Studies indicate the effects of the fruits of Goji berry on aging, neuroprotection, fatigue, energy expenditure, glucose control in diabetics, antioxidant properties, immunomodulation, anti-tumor activity, and cytoprotection. Some authors report that antioxidant molecules found in goji fruit might offer many health protective benefits by alleviating oxidative stress, when used as an additive or in a mixture with other phytochemicals in fruit or herbal products.

It was found that Goji berry fruit growing in Bulgaria has a total polysaccharide content of about 4%. The content of total polyphenol compounds in the extracts was found to be between 5.5mg and 8mg GAE/g of dry product. Polyphenols from dry Goji berry fruit were extracted and studied by HPLC analysis for the type of polyphenols present. Antioxidant activity of extracts rich in polyphenols was determined by DPPH, FRAP and CUPRAC methods. The data was compared with a medicinal product containing an extract of Goji berry, where a synergistic reaction was also established. Inhibitory effects of the Goji berry extracts and their corresponding polyphenols were investigated in the presence of α-glucosidase for antidiabetic activity. The study demonstrated that some of the polyphenols in the investigated extracts exhibit competitive properties towards the enzyme.