Evaluation of anti-glycation activities of phlorotannins in human and bovine serum albumin-methylglyoxal models

Abstract

In this study, the anti-glycation activities of phlorotannins contained in the Japanese Lessoniaceae (Ecklonia cava, Eck. kurome, Eck. stolonifera, Eisenia arborea, and Eis. bicyclis) were tested using serum albumin-methlglyoxal (MGO) models. In the human serum albumin (HSA)-MGO model and the bovine serum albumin (BSA)-MGO model, the concentrations of crude phlorotannins at 50% inhibition (IC50) of fluorescent advanced glycation end products (AGEs) formation was in the range of 0.45 to 0.53 mg/mL and 0.43 to 0.53 mg/mL, respectively. Among the purified phlorotannins, phlorofucofuroeckol A with the benzobisbenzofuran skeleton had the highest inhibitory activities (IC50: 4.8 × 102 μM in HSA-MGO model and 4.1 × 102 μM in BSA-MGO model) against fluorescent AGEs formation, and showed about 13 times the inhibition in the HSA-MGO model, and about 20 times the inhibition in the BSA-MGO model, with respect to aminoguanidine hydrochloride, which was used as a positive control. In the test on MGO-scavenging activity using HPLC analysis, it showed that eckol and its simple dimers (dieckol and 8,8′-bieckol) had higher scavenging rate than aminoguanidine hydrochloride. In addition, it was revealed by liquid chromatography-electrospray ionization-mass spectrometry that eckol reacted with MGO and formed two adducts with it. These results strongly suggest that phlorotannins are novel and effective anti-glycation substances derived from natural plants.