Production of GABA-enriched idli with ACE inhibitory and antioxidant properties by Aspergillus oryzae: antihypertensive effects in spontaneously hypertensive rats
The present study aimed to develop a fermented food (idli) with enhanced γ-aminobutyric acid (GABA) and Angiotensin I-Converting Enzyme (ACE) inhibitory properties using a GABA-producing fungus. Aspergillus oryzae NSK fermented idli batter and GABA was maximized (451.7 mg/kg) at 120 h. ACE inhibitory, 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) free radical activities and nitric oxide radical scavenging activities increased to 41.8%, 1.9 and 0.6 µMol Trolox Equivalents Antioxidant Capacity (TEAC) per gram at 120 h, respectively. In contrast, phytic acid and trypsin inhibitor activities decreased to 3.01 g/kg and 30.8 mg/kg, respectively. Systolic blood pressure of spontaneously hypertensive rats in fermented idli diet group was lower than those fed by plain idli diet. Lipid peroxidation in plain idli diet group was significantly higher, whereas superoxide dismutase and glutathione reductase activities were significantly lower. Expression of ET-1, HSP70, NF-κB and iNOS genes in aorta of SHRs receiving GABA-containing diets down-regulated between 2.2 - 3.8 folds. Production of GABA-enriched foods can be a promising approach to lower blood pressure of spontaneously hypertensive rats.