4.2.3. Antioxidant and Free Radical Scavenging Activities of Extract

Antioxidant activity—reducing power: The ferric reducing antioxidant power (FRAP) technique was used to measure in vitro antioxidant activity [37]. An amount of 1 mL ascorbic acid (0–100 µg/mL) or garlic extract (0–100 µg/mL) was combined with 2.5 mL in phosphate buffer (0.1 M, pH 6.6) and 1% potassium ferricyanide (2.5 mL). After 20 min at 50 ◦C, 2.5 mL of trichloroacetic acid (10%) was added to the test tubes to terminate reaction. The mixtures were subsequently centrifuged at 3000 rpm for 10 min, causing the formation of supernatant. Finally, freshly made ferric chloride (0.5 mL, 0.5%) solution was mixed with the supernatant (2.5 mL) and distilled water mixture (2.5 mL). The absorbances of various samples were measured at 700 nm.

Percentage free radical scavenging activity = [(Xcontrol - Xsample)/Xcontrol] × 100

Xcontrol = absorbance of control sample.

Xsample = absorbance of sample in the presence of extract.

Analysis of free radical scavenging activity by DPPH method: Antioxidant activity of aqueous garlic extracts was estimated using 1,1 difenyl-2-picryl-hydrazyl (DPPH) as

published before [12]. Dry powder was obtained from the aqueous extract of garlic. This was dissolved in methanol. One milliliter of 0.3 mM DPPH in methanol was added to the extract solution test sample (2.5 mL) of varying concentrations (0–100 µg/mL) and incubated in the dark for 30 min at room temperature. All samples were read at 517 nm with methanol used as a blank. Inhibitory effect of DPPH was calculated according to the following equation:

Percentage of free radical scavenging activity = [(Ac − As)/Ac] × 100

where, Ac = absorbance of control, and As = absorbance in presence of extract.
