Nutraceutical benefits and neuro-protective potent of four colored peppers (Capsicum annuum var. grossum).

Background: Four colored peppers (Capsicum annuum var. grossum), orange, purple, yellow and red, are plant foods served as salad or stir-fry for meals in Taiwan and many countries. Purpose: This study aimed to investigate the multiple nutraceutical properties of aqueous extracts prepared from colored peppers. Methods: Vitamin C content and phytochemical profiles of these peppers were analyzed. In vitro effects of anti-oxidative, anti-α-amylase, anti-α-glucosidase, anti-lipase and anti-acetylcholinesterase (AchE) of pepper aqueous extracts at 0.25, 0.5 and 1 mg were evaluated. The neuronal protective potent of pepper aqueous extracts at 0.5 and 1 mg in high glucose treated nerve growth factor (NGF)-differentiated PC12 cells were examined. Results: Vitamin C content in these peppers was in the range of 60-96 mg/100 g fresh weight. The content of phenolic acids, flavonoids, anthocyanins and triterpenoids in these peppers was in the range of 860-2185 mg/100 g dry weight. Pepper aqueous extracts at 0.25, 0.5 and 1 mg exhibited concentration-dependent radical scavenging effects, ironchelating effects and reducing power, as well as effectively inhibited α-amylase, α-glucosidase, lipase and AchE activities. High glucose increased Bax mRNA expression, decreased mitochondrial membrane potential and Na+-K+ ATPase activity, caused DNA fragmentation and massive Ca2+ release, stimulated oxidative and inflammatory responses, and led to death of NGF-differentiated PC12 cells. Pre-treatments of pepper aqueous extracts at 0.5 and 1 mg reversed these changes, and increased the viability of NGF-differentiated PC12 cells. Conclusions: These novel findings suggest that colored peppers offered many bio-functions, which might benefit the prevention of diabetes associated complications such as diabetic neuropathy.