Antiglycation effects of extracts from six pomelo cultivars

Abstract

Chronic hyperglycemia promotes the formation of non-enzymatic protein glycation, leading to the production of advanced glycation end-products (AGEs), which play a significant role in the development of complications such as diabetic nephropathy and neuropathy. Immense efforts have been devoted into finding effective antiglycation compounds from dietary plants and fruits for prevention and the treatment of diabetic complications. Pomelo (Citrus grandis (L.) Osbeck), one of the Thailand’s largest citrus fruits, contains of many flavonoids that have shown to beneficial effects on human health. The objective of this study was to quantify of flavonoids in six pomelo cultivars (Tar Koi, Kao Nam Pueng, Kao Tanggwa, Thong Dee, Tubtim Siam and Kao Yai) and to determine the preventive effect of the six pomelo cultivars against a fructose induced non enzymatic glycation assay of bovine serum albumin (BSA). The results revealed that the six pomelo cultivars contained of naringin, hesperidin, neohesperidin, neohesperidin dihyrodchalcone, naringenin and hesperitin. It was found that the six pomelo cultivar extracts (0.25-2.00 mg/ml) significantly inhibited the overall formation of AGEs and N-(carboxymethyl)lysine (CML) in a concentration-dependent manner. In addition, the six pomelo cultivar extracts decreased the formation of fructosamine, which is directly associated to the reduction of the AGE formation. The pomelo cultivar extracts were also able to suppress the formation of protein oxidation through its ability to increase levels of thiol groups and reduce the amount of protein carbonyl formation, indicating of protection of protein oxidation in BSA. Moreover, the pomleo cultivar extracts showed abilities in suppressing formation of amyloid cross linked β-structures of BSA, suggesting of a reduced risk in developing debilitating degenerative diseases. These results reveal that the six pomelo cultivar extracts may be a useful dietary supplement for preventing AGE-mediated diabetic complications.