Antioxidant and antidiabetic potential of Curcuma longa and its compounds

Antioxidant agent can eliminate the free radicals due to oxidative stress that has been reported as the main cause of diabetes mellitus. This study evaluated the effect of Curcuma longa rhizomes and its compounds curcumin and bisdemethoxycurcumin as antioxidants and antidiabetic activity. The phytochemical assay was performed with modified Farnsworth method. Quantitative curcumin, bisdemethoxycurcumin and curcumol of C. longa extract (CLE) were evaluated using HPLC. The antioxidant assay was performed with 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzo thiazoline-6-sulfonate acid) (ABTS) and Ferric Reducing Antioxidant Power (FRAP) assay. Antidiabetic properties were measured by inhibitory activity of α-, β-glucosidase, and α-amylase. This study suggested that CLE has terpenoids in high level. Based on HPLC test, CLE contained curcumin (16.92%), curcumol (15.51%), and bisdemethoxycurcumin (5.27%). Bisdemethoxycurcumin has DPPH scavenging activity (IC₅₀= 64.94±2.44 μg/ml), curcumin has the highest activity (IC₅₀=0.92±0.03 μg/ml) in ABTS assay, while CLE has the highest activity in FRAP assay (IC₅₀=311.10 μM Fe(II)/μg) in the highest concentration (250.00 μg/ml). In antidiabetic assay, bisdemethoxycurcumin has the highest in α-glucosidase and α-amylase inhibitory activity (IC₅₀=3.76±0.33 μg/ml; 1.79± 0.15 μg/ml), while in β-glucosidase inhibitory activity curcumin has the highest activity (IC₅₀=1.03±0.03 μg/ml). CLE and its compounds possess antioxidants and antidiabetic activities.