Antiglicative activity of the water soluble fraction from coffee silverskin

Abstract

Recently, the accumulation of Advanced Glycation End-products (AGE) in human tissues and organs has been implicated as a major pathogenic process in diabetic complications, atherosclerosis, Alzheimer¿s disease and aging. In this sense the possibility of using the roasted coffee silverskin (CS), a byproduct of roasted coffee beans, as an antiglycative ingredient has been evaluated, but maintaining an environment friendly method of extraction. CS is the outer layer of the roasted coffee beans. Water soluble fraction from an Arabica roasted CS was obtained, freeze-dried, and characterized by its antioxidant activity. Antiglicative activity of CS extract was evaluated in BSA-glucose (21 days; Ext/Emm. 360/420) and BSA-methylglyoxal (14 days; Ext/Emm. 340/420) assays in the range of 0.5 to 25 mg/mL. Reaction mixtures were prepared containing 10 mg BSA in 100 mM saline phosphate buffer (pH 7.4) containing sodium azide, EDTA, and penicillin-G and incubated at 37 °C. Then, triplicate 100 ¿L aliquots were removed and their fluorescence intensity and scan of fluorescence (emission) was measured in a spectrofluorometer platereader (Synergy-MX, BioTek Instruments, USA). In both assays, aminoguanidine (0.4 mg/mL, > 90 % inhibition) was used as reference. To determine whether the extracts themselves interfered with fluorescence (quenching), each extract was tested in the absence of BSA for 14 and 21 days. Glycated BSA is an indicator of the extent of the reaction and was reduced significantly in presence of the aqueous extract from CS. IC50 was 8.2 ± 0.26 mg/mL and 3.9 ± 0.1 mg/mL for BSA-MGO and BSA-Glc assays, respectively. In the reaction media, IC50 values represent an effective concentration of 1.17 mg of CS extract per 10 mg BSA and 0.23 mg MGO for the BSA-MGO assay; and 0.56 mg CS extract per 10 mg BSA and 100 mg glucose for the BSA-Glc assay. Intrinsic fluorescence was subtracted from calculation and represent 2.4% and 8.2% for BSA-MGO and BSA-Glc, respectively at 1 mg/mL. CS could offer a potential therapeutic approach for the prevention of diabetic or other pathogenic complications induced by AGEs. Acknowledgement: This research was supported by NATURAGE (AGL2010-17779) project. Correspondence to: fjmorales@ictan.csic.es Keywords: Advanced Glycation End-products, coffee silverskin, glycation, antiglycative activity