- By Mizpah C. Villalobos, M.S. and Leojen F. Torres
ABSTRACT
Spent coffee grounds (SCG) are important waste products from coffee brews which can be valorized for the recovery of bioactive compounds. This study was aimed at recovering bioactive components from SCG fractions with potential in vitro antidiabetic and antioxidant activities. Bioactive compounds were extracted from SCG of the Robusta (Coffea canephora) variety, and fractionated on a silica gel column using solvents acetone, acetone-methanol combinations, and methanol. The fractions obtained were assayed in vitro for α-amylase and α-glucoside enzyme markers for diabetes; 2, 2-diphenyl-1-picrylhydrazyl (DPPH) inhibitions, and ferric reducing antioxidant power (FRAP) antioxidant activities; and the total phenolic content (TPC) and total flavonoid content (TFC). Seven fractions were obtained from the crude SCG extract (2.138 g) with the acetone fraction having the highest yield of 0.74 g. Among the fractions, only the acetone fractions had moderate α-amylase inhibitory activity, but none of the fractions had α-glucosidase inhibitory activity. The standard drug acarbose had IC50 values of 22.63% and 90.21% for α-amylase and α-glucosidase enzymes, respectively. The methanolic fractions had the greatest DPPH inhibition at 93.6 – 94.2% which is close to ascorbic acid standard at 97.7%, while the acetoNe-methanol (2:3) fraction had the highest FRAP ACTIVITY OF 189.6 μM ascorbic acid equivalents. The acetone-methanol (2:3) fraction had the highest TPC of 210.63 μg catechin equivalents (CE0 oer mg fraction, and the acetone and acetone-methanol (2:3) fractions had the highest TFC of 108.7 and 114.26 μg CE per mg fraction, respectively. Antioxidant activities may be due to the presence of the phenolic and flavonoid content in the fractions, while α-amylase inhibition potential may due to flavonoids. Thin layer chromatography further confirms the presence of phenolics and flavonoids in the fractions. Thus, bioactive fractions with α-amylase inhibition and antioxidant activities were recovered from SCG. These can be further developed into functional foods and/or nutraceutical products to help prevent the development of hyperglycemia, type 2 diabetes, and oxidative stress.