2.3. Antioxidant assays
The antioxidant concentration of the Roselle extract was routinely measured by the FRAP method using a Roche Cobas Fara II analyser (Roche, Basel, Switzerland; Benzie & Strain, 1996). ORAC was also measured as it is frequently used as an international standard (Cao & Prior, 1999). TAS was determined using a kit supplied by Randox Laboratories Ltd (Co. Antrim, UK.). Both ORAC and TAS were also measured on a Roche Cobas Fara II analyser.
2.4. Total phenolic compounds assay
Total soluble phenolics in the Roselle extract were determined with Folin-Ciocalteu's reagent by the method of Slinkard and Singleton (1977) using gallic acid as a standard.