In vitro antidiabetic and antioxidant activities of elettaria cardamomum l. (cardamom), piper cubeba l. (cubab), and plumeria rubra l. (frangipani)

Abstract

Diabetes is a chronic common disease, prevalence of diabetes is increasing worldwide; this urges the need for more new treatment. Inhibition of intestinal α-amylase and α-glucosidase is an important strategy to control post-prandial hyperglycemia associated with type 2 diabetes mellitus. Based on the fact that plants have been the basis for the treatment of several diseases, selected plants will be used for this study. Antioxidants present in plants can prevent the development of diabetic; hence, measurement of antioxidant activity of the plants will also be carried out. The general objective of this study is to investigate the role of Elettaria cardamomum L. (Cardamom), Piper cubeba L. (cubab), and Plumeria rubra L. (Frangipani) in the treatment of diabetes mellitus through its hypoglycemia and antioxidant activities in-vitro.The dried plant were extracted with distilled water and methanol and freeze dried. The dried extract of the plant were examined for the alpha-glucosidase inhibition and pancreatic alpha-amylase inhibition. Extracts were further quantified for their antioxidant activities through DPPH test, FRAP test and screened for the total phenolic content (TPC) and total flavonoids content (TFC). Among the six extracts studied, aqueous extract of Piper cubeba L. (cubab) and Elettaria cardamomum showed satisfactory inhibitory effects on both enzymes with higher inhibitory effect shown on α-glucosidase compared to α-amylase activity, also they showed good in-vitro antioxidant activities. The inhibition for α-glucosidase were 10.41 (0.03), 95.19 (0.01), and -2.92 (0.03) for Elettaria cardamomum L. (cardamom), cubeba L. (cubab) and Plumeria rubra L. (frangipani) water extracts respectively, while for cardamom, cubab, and frangipani methanolic extract the inhibition percentage were 13.73(0.02), 92.77 (0.01), and -0.98 (0.01) respectively. The highest inhibitory activities (%) were shown in both of the Piper cubeba L. (cubab) extracts. The α-amylase inhibition for Elettaria cardamomum L. (cardamom), cubeba L. (cubab) and Plumeria rubra L. (frangipani) water extracts were 82.99 (0.01), 64.35 (0.01), and 20.28 (0.02) respectively, while for cardamom, cubab, and frangipani methanolic extract the inhibition percentage were 39.93 (0.01) , 31.06 (0.02), and 39.40 (0.01) respectively. The highest inhibitory activities (%) were shown in both of the cardamom extracts. For in-vitro Antioxidant activities, the water extract of cubab showed significant antioxidant activity in vitro in scavenging DPPH radical, FRAP, TPC and TFC followed by cardamom and frangipani. Further optimization studies were performed on Piper cubeba L. and Elettaria cardamomum water extracts. The optimization has increased the Elettaria cardamomum α-glucosidase inhibitory activity. Moreover, the three water extracts were combined in a certain percentages and the results showed cubeb had the better results. The results obtained from the study reveals the in vitro antidiabetic activities of Piper cubeba L. and Elettaria cardamomum through α-glucosidase and α-amylase inhibition, and indicate that these plants can be considered as potential plants the management of diabetes mellitus.