Glucose lowering effect of standardized extract of centella asiatica ECa233 in vitro and in vivo Thai silk worm model

Abstract

This study aims to test the effect of ECa 233 and some compounds (asiaticoside and madecassoside) in lowering glucose by the mechanism of inhibition of α-glucosidase both in vitro and in vivo using Thai silkworm model. In vitro study was utilized to evaluate the inhibition of yeast and intestinal α-glucosidase from rat of the test compounds and determine the IC₅₀ value. Acarbose, ECa 233, asiaticoside and madecassoside showed the inhibition of yeast α-glucosidase with IC₅₀ value 0.0008, >500, 92.42 and 68.89 mg/ml, respectively and inhibition of intestinal α-glucosidase from rat with IC₅₀ value 0.005, 205.61, 21.81 and 50.52 mg/ml, respectively. In vivo study in Thai silkworm model was used to test the toxicity and determine the LD₅₀, the results showed that the LD₅₀ value of ECa 233, asiaticoside and madecassoside injected via intra-midgut in Thai silkworm was 178.51, >125 and >250 mg/ml, respectively and the LD₅₀ value of ECa 233, asiaticoside and madecassoside injected via intra-hemolymph in Thai silkworm was 46.92, >125 and 174.58 mg/ml, respectively. Then the hypoglycemic effect of the test compounds was determined using hyperglycemic Thai silkworm model induced by feeding diet mixed with 10% glucose or 10% sucrose or 10% maltose. It was found that sugar level in Thai silkworm hemolymph fed with 10% glucose, 10% sucrose and 10% maltose diet lowered with statistical significance using insulin comparing with the control group (P< 0.05). Acarbose also lowered the sugar level in diet mixed with 10% sucrose and 10% maltose diet with statistical significance comparing with the control group (P< 0.05). For intra-midgut administration, asiaticoside (50 mg/ml) and madecassoside (5, 50 mg/ml) lowered the sugar level in diet mixed with 10% sucrose whereas asiaticoside (0.05, 0.5, 5, 50 mg/ml) and madecassoside (0.05, 0.5, 5, 50 mg/ml) lowered the sugar level in diet mixed with 10% maltose with statistical significance comparing with the control group (P< 0.05). For intra-hemolymph administration, ECa 233 (0.05, 0.5, 5 mg/ml), asiaticoside (5, 50 mg/ml) and madecassoside (50 mg/ml) lowered the sugar level in diet mixed with 10% glucose whereas ECa 233 (5 mg/ml), asiaticoside (50 mg/ml) and madecassoside (50 mg/ml) lowered the sugar level in diet mixed with 10% sucrose. Moreover ECa 233 (0.5, 5 mg/ml), asiaticoside (0.05, 0.5, 5, 50 mg/ml) and madecassoside at (0.05, 0.5, 5, 50 mg/ml) lowered the sugar level in diet mixed with 10% maltose with statistical significance comparing with the control group (P< 0.05).