Assay of mushroom tyrosinase activity
In order to assay the inhibitory action of M. grandiflora L. flower extract (final concentration 10, 15, 20%; v/v) on mushroom tyrosinase, dose-dependent inhibition experiments were carried out in triplicate, as described previously,with a minor modification [32]. Briefly, 10 μL of aqueous solution of mushroom tyrosinase (200 units)
was added to a 96-well microplate, in a total volume of 200 μL mixture containing 5 mM L-DOPA which is dissolved in 50 mM phosphate buffer (pH 6.8). The assay mixture was incubated at 37°C for 30 min. Following incubation,The amount of dopachrome produced in the reaction mixture was determined spectrophotometrically at 490 nm (OD490) in a microplate reader. The inhibition percentage at three doses for each experiment was calculated by the following equation: inhibition percentage of tyrosinase activity (%) = (B-A) A× 100, where B is the mean of the measured OD490 values of the blank control,
and A is the mean of the measured OD490 values for the M. grandiflora L. flower extract treated group.