Abstract:
Coffee silverskin (CS) is a major by-product of the coffee roasting process which is a source of antioxidant compounds. In this research, CS is extracted to locate the optimum extraction condition as a function of three variables including the polarity of solvent (water, 50% ethanol and 100% ethanol), temperature (35, 40, 50, and 60 ◦C), and extraction time (30 and 60 minutes) by using solid/solvent ratio 1:25 g/ml. The extraction yield, phenolic content, the chemical fingerprint profile of the CS extract were evaluated using TLC, the contents of caffeine, and chlorogenic acid using HPLC. Furthermore, the biological activity including DPPH antioxidant activity and antimicrobial of S. aureus has also been investigated. The result demonstrated that the best condition for CS extraction is with 100% ethanol at 60 ◦C for 30 minutes. This condition resulted in the extraction yield of approximately 6-7%, the phenolic content (29.93 mg GAE/g extract), the caffeine content (59.38 mg/g extract). It could also inhibit bacteria growth and DPPH radical (IC50 = 0.28 mg/ml). For these reasons, the extracted CS has great potential to be applied for further use in the industrial sector due to the use of eco-friendly, safe, and cost-efficient extraction technology, as well as the high level of antioxidant activity embedded in the CS extract.