2,2’-Diphenyl-1-picrylhydrazyl radical (DPPH), Folin-Ciocalteu Phenol reagent, sodium carbonate, β-carotene, linoleic acid, Tween 40, sodium nitrite, aluminum chloride, sodium hydroxide, ascorbic acid, gallic acid and quercetin were obtained from Sigma-Aldrich (Sigma Chemical Co., St Louis, MO, USA). All the chemicals were of analytical grade.
2.2. Preparation of Plant Extracts
The whole fruits of B. racemosa and H. sabdariffa were collected from Kepala Batas, Pulau Pinang, Malaysia. The fruits were cleaned and separated from the seed. The fruits were dried in an oven, at an average temperature of 40 °C. Then, the fruits were grounded into powders. Dried powder of B. racemosa and H. sabdariffa fruit respectively were macerated with methanol at a ratio of dry weight: solvent of 1:10 (w/v). The extracts were filtered and evaporated on rotary evaporator to yield a crude residue. The crude extracts were stored in refrigerator and were evaluated for total phenolic content, total flavonoid content as well as antioxidants activity.
2.3. Determination of Total Phenolic and Total Flavonoid Content
The total phenolic contentof the extracts were measured using Folin Ciocalteu 's reagent according to the literature with some modifications . Briefly, 0.1 mL extracts (1 mg/mL) was mixed with 1.0 mL Foline Ciocalteau phenol reagent and allowed to react for 3 min. Then, 300 mL of 1N Na2CO3 was added and incubated at room temperatue for 90 min. Gallic acid (0.02-0.64 mg/mL) was used as