Dear

Dr. Gruia is right. Both these compounds are well known antioxidant. The DPPH is simple and accurate procedure. Total phenolic content can be determined by different methodologies e.g. folin methodology or HPLC procedure. However I suggest you to detect the IC50 value, due it's more accurate in the determination of antioxidant properties. 

Good luck

Hi Maria, when you use DPPH method you can do the calibration curve with vit. C, but you can also use vit. E. I measured antioxidant activity with DPPH method on various plant extracts on a spectrophotometer.

ALex :-)

Dear

Dr. Gruia is right. Both these compounds are well known antioxidant. The DPPH is simple and accurate procedure. Total phenolic content can be determined by different methodologies e.g. folin methodology or HPLC procedure. However I suggest you to detect the IC50 value, due it's more accurate in the determination of antioxidant properties. 

Good luck

Free radical scavenging activity using DPPH radical

The antiradical activity of pumpkin sample, based on the scavenging activity of the stable free radical, DPPH (2,2-diphenyl-2-picrylhydrasyl)(C18H12N5O6) will be estimated according to the method of (Turkmen, et al., 2006). Each extract (0.5 ml) will be added to 1.5 ml DPPH solution in methanol (0.1 mM). Absorbance at 517 nm will be determined after 60 min at room temperature in the dark. The percentage inhibition activity will be calculated from [(A0 − A1)/A0] × 100. A0 is the absorbance of the control, and A1 is the absorbance of the extract.  

Hi, there are no particular conditions to perform the DPPH assay in onion extracts. Either way, you can read this article, in which the DPPH activity was performed in onion extracts http://www.sciencedirect.com/science/article/pii/S0308814616300954

Hello Maria,

You can either use Vit E or Ascorbic acid.I prefer using Ascorbic acid.

Hi Maria you can use Vit C , i measured antioxidant activity with DPPH method by using Trolox as a standard

Hi Maria,

You can use Vit E and Ascorbic acid, but in the literature the best one is Trolox, you can use also BHT to measure antioxidant activity with DPPH assay

Happily you can use Ascorbic acid (as it comparatively economical to Vit E). It should give you excellent results.

Hi Maria

Free radical scavenging assay using 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH) was carried out according to Yildirim et al., (2001). This method is based on the reduction of alcoholic DPPH solution. The odd electron of DPPH shows an absorption maximum at 517nm (purple color). As the odd electron of the radical becomes paired off in the presence of a hydrogen donor (the antioxidant), the absorption strength vanishes, and the resulting decolorization is stoichiometric with respect to the number of electrons capture

Reagents:

·       1mM 1, 1 Diphenyl-2-picrylhydrazyl (DPPH). A weight of 0.394 g DPPH was dissolved in 1L of 95% ethyl alcohol. also use ascorbic acid.

% Scavenging activity= [(control absorbance-sample absorbance) / control                                   absorbance)] × 100.

with my best regards

Dear Maria Romo,

You can use following procedure...

0.2 mL of different extracts and standard (1 mg/mL) was mixed with 3 mL of methanolic solution of DPPH (0.004%). Then, the incubation (30 min) of different samples was done in the dark at room temperature. Finally, the result of absorbance was read at 517 nm. The following equation was used to calculate the results of DPPH free radical percentage inhibition (I %):

I % [DPPH free radical] = [(AC – AS) / AC] × 100

where AC and AS are the absorbance of the control and samples or standard. The each sample was analyzed in triplicate.