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SECTION I: MOLECULAR GENETIC ENGINEERING AND BIOCHEMICAL TECHNOLOGY 652.4. Inhibition of %u03b1-glucosidase assayThe %u03b1-glucosidase inhibitory protocol was carried out according to previously assay with slight modification [25]. Extracts and compounds were dissolved in DMSO and diluted with phosphate buffer (pH 6.8) to various concentrations of 250, 100, 50, 25 and 10 %u00b5g/ml. In a 96-well plate, a reaction mixture containing 100 %u00b5L of phosphate buffer (100 mM, pH 6.8), 40 %u00b5L of extracts or compounds, 20 %u00b5L %u03b1- glucosidase (0.4 U/mL, CAS No 9001-42-7, Sigma) were pre-incubated for 15 min at 37 %u00b0C. Then, 40 %u00b5L substrate p-nitrophenyl-%u03b1-D-glucopyranoside (pNPG, 2.5 mM, CAS No 3767-28-0, Sigma) were added to the mixture. The reaction was stopped by 100 %u00b5L of Na2CO3 (0.1 M) for each well after 20 min incubation. Well without test compound was set up as a blank control and acarbose was used as a positive control. Experiments were done in triplicates. The absorbance of the released p-nitrophenol was measured at 405 nm with microplate reader (BioTek, USA). The results, expressed as percentage inhibition, were calculated using equation (1):Inhibition (%) = [(OD control %u2013 OD sample) / OD control] x 100 (1)The IC50 value showed the concentration of compound inhibiting 50% of %u03b1-glucosidase activity. The IC50 value was calculated using TableCurve software.3. RESULTS AND DISCUSSIONThe total methanol residue, n-hexane extract and chloroform extract from the rhizomes of Z. zerumbet were evaluated for %u03b1-glucosidase inhibitory activity using acarbose as the positive control. All the three samples exhibited inhibitory effect against %u03b1-glucosidase, in which chloroform extract showed the most effective activity with IC50 value of 126.9 %u03bcg/mL, slightly lower than that of acarbose. As for the results, chloroform extract was chosen