Changes in the antioxidant activities and angiotensin-I converting enzyme inhibitory protein during the germination of green coffee beans

Germinated green coffee beans can be potential dietary sources of bioactive compounds. In this study, two varieties of coffee beans (arabica and robusta) germinated at 28 °C for 0-15 days. The antioxidant and angiotensin-I converting enzyme (ACE-I) inhibitory activities were measured by the antioxidant capacities (ABTS•+, DPPH, •O2, and •OH) and in vitro ACE-I inhibition assay. Significant differences (p < 0.05) in soluble protein and free amino acid contents were noted within and between coffee beans before and after germination. Antioxidant activity increased in robusta and arabica coffee beans after germination when seen from the total amino acid antioxidant (TAntAA)/total amino acid (TAA) ratio analysis of 0.32 and 2.36%, respectively. The DPPH and ABTS•+ radical scavenging activity were higher after germination for 10 days in all the coffee beans as compared with the ungerminated beans (0 days);however, •O2 and •OH scavenging radical activity did not show the same effect in both treatments. Out of the legumes studied, germinated coffee arabica and robusta beans can be used in the dietary management of hypertension as their hydrolyzed protein showed >82% ACE inhibition, reaching an IC50 value of 2.57 and 1.47 μg/mL, respectively. Key words: Bioactive protein; robusta; arabica; ACE-Inhibitor; antioxidant activity.