Evaluation of Antidiabetic and Antioxidant Activities of L-carnosine using Enzyme Inhibition and Free Radical Scavenging Assays: An In-vitro Study

Abstract

Introduction: Diabetes is a chronic disease that causes dysfunction of various organs and tissues resulting in end organ damage and premature mortality. Oxidative stress is a main factor of diabetic complications. There is a need for the development of safer therapeutic agents for diabetes, due to the adverse effects of conventional drugs. L-carnosine is a dipeptide synthesised by the body from β-alanine and L-histidine. It is reported to have heavy metal chelating, pH buffering, anti-inflammatory property and neuroprotective effect making it a prospective drug target for chronic diseases like diabetes. The antidiabetic property of L-carnosine and its free radical scavenging potential have not yet been fully explored. Aim: To evaluate the in-vitro antidiabetic and antioxidant activities of L-carnosine. Materials and Methods: The present in-vitro study was conducted in the Department of Pharmacology at Sri Ramachandra Medical College and Research Institute, Porur, Chennai, India. The duration of the study was one month, done in December 2020. The in-vitro antidiabetic property of L-carnosine was evaluated using α-glucosidase and α-amylase inhibition. About 20, 40, 60, 80, 100 μg/mL concentrations of L-carnosine and acarbose were used for the study wherein, acarbose was used as the standard. The absorbance values were taken in spectrophotometer at 405 nm and 540 nm for α-amylase and α-glucosidase enzyme, respectively. Further, the antioxidant activity of L-carnosine was determined at the same concentrations using 2,20-azino-bis (3-ethylbenzthiazoline6-sulfonic acid) (ABTS) assay with Butylated Hydroxytoluene (BHT) as standard. The spectrophotometric absorbance was read at 734 nm. The data analysed were presented as percentage inhibition. The percentages of enzyme inhibition for various concentrations were compared between the standard and L-carnosine. Results: The inhibitory percentages for α-glucosidase enzyme at concentrations of 20,40,60,80 and 100 μg/mL of L-carnosine were 28.61%, 36.01%, 45.33%, 53.05%, 62.70% respectively. The percentages for α-amylase inhibition at concentrations of 20, 40, 60, 80 and 100 μg/mL were 18.18%, 31.81%, 45.45%, 59.09% and 72.12%, respectively. The free radical scavenging activity by ABTS assay for 20, 40, 60, 80 and 100 μg/mL concentrations of L-carnosine were 34.40%, 36.65%, 38.04%, 40.51% and 43.30%, respectively. L-carnosine exhibited significant inhibition of α-glucosidase and α-amylase enzyme in dose-dependent manner. The result of the ABTS assay showed that L-carnosine possessed significant free radical scavenging property in a concentration-dependent manner. Conclusion: Results showed L-carnosine had considerable α-glucosidase inhibitory activity, α-amylase inhibitory activity, as well as, ABTS radical scavenging activity. The present findings indicate that, L-carnosine has in-vitro antidiabetic and antioxidant activity. Hence, the present study supports further evaluation and use of L-carnosine for the management of diabetes and as an antioxidant in nutraceuticals.