(i) Set up a calibration curve in five tubes: dilute 0.18 mg/mL glucose solution with distilled water to prepare solutions 0, 0.1, 0.2, 0.3 and 0.4 mM. Label tubes from 1 to 5. Then, add 0.5 mL of 0, 0.1, 0.2, 0.3 and 0.4 mM glucose to tube 1, 2, 3, 4 and 5, respectively.
(ii) Set up your experimental assay tubes and prepare tubes 6 and 7 adding 0.25 and 0.50 mL of a plant extract, respectively. Complete volume of tube 6 to 0.5 mL with distilled water.
(iii) Add 0.5 mL of Somogyi reagent to each tube. Cover the mouth of each tube with a glass marble and put the tubes in a boiling water bath for
15 minutes. Let cool to room temperature. Add 0.5 mL of Nelson reagent to each tube and swirl.
(iv) Add 1 mL of distilled water to each tube and vortex.
(v) Read absorbance at 520 nm using a 1 cm path length (1 mL) microcuvette.
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