of DPPH and the reaction mixture was shaken vigorously. The tubes were allowed to stand at room temperature for 30 min. Each reaction mixture was then placed in the cuvette holder of a Perkin Elmer-Lamda 25 UV/Vis spectrophotometer and mon- itored at 517 nm against blank which used methanol as the baseline correction. The scavenging ability was calculated as follows: Scavenging ability (%) = 100 x [Absor-
Fig. 2. Total phenols of different M. fruticosum flower extracts. Values represent averages ± standard deviations for triplicate experiments. HEX ext; hexane extract, DCM ext; dichloromethane extract and MET ext; methanol extract.
bance of control - Absorbance of sample/Absorbance of control]. The antioxidant
activity of all samples was expressed as IC50 which was defined as the concentration
acid was y = 0.00515x
- 0.00400 (R2 = 0.999) where y is the absorbance and x is
(in lg/ml) of oil required to inhibit the formation of DPPH radicals by 50%. The experiment was carried out in triplicate. The results of mean values and the stan- dard deviation obtained are shown in Fig. 1.
2.6.2. Determination of total phenolic contents
Total phenolic content of all samples obtained from M. fruticosum flowers was determined using the Folin–Ciocalteu reagent according to the modified method of Singleton and Rossi (1965) with gallic acid as the standard. The solution (0.2 ml) was mixed with 1.0 ml of Folin–Ciocalteu reagent, 1.0 ml of an aqueous solution of 7% Na2CO3 and 5.0 ml of distillated water, respectively. The mixture was then vortexed vigorously. The reaction mixtures were allowed to stand for
30 min before absorbance at 765 nm was measured. The same procedure was also applied to the standard solutions of gallic acid. The calibration equation for gallic