Potassium ferricyanide

The ferric-reducing antioxidant power of the aqueous and methanolic stem bark extracts of L. eriocalyx was determined following the methods described by Oyaizu [28 ] and Benzie and Strain [29 ]. Briefly, 1 ml of assay extracts or L-Ascorbic acid at concentrations ranging from 0.01 μg/ml to 1000 μg/ml were mixed with 2.5 ml of phosphate buffer (200 mM, pH 6.6) and 2.5 ml of 30 mM potassium ferricyanide (Lot No# SL60061402; Loba Chemie). The mixtures were then incubated in a water bath set at 50 °C for 20 min, after which aliquots of 2.5 ml of Trichloroacetic Acid (TCA) (600 mM) was added, mixed and centrifugation was done at 3000 rpm for 15 min. After that, 2.5 ml of the supernatants were carefully aspirated and mixed with 2.5 ml of distilled water and 0.5 ml of 6 mM ferric chloride (FeCl_3; Lot No# A21440164, Loba Chemie). The absorbances of respective supernatants were measured at 700 nm against blank using a double beam UV-spectrophotometer (Shimadzu UV-Vis 1601).

ABTS [2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)], trichloroacetic acid (TCA), and DPPH (1,1-diphenyl-2-picrylhydrazyl) were procured from Sigma (Sigma-Aldrich GmbH, Sternheim, Germany). Potassium Ferricyanide from Loba Chemie Pvt. Ltd. (Mumbai, India) and ascorbic acid was obtained from SD Fine Chem. Ltd. (Biosar, India) while indomethacin and phenylbutazone were purchased from Spimaco (Saudi Arabia). The rest of chemicals and solvents used were of analytical grade and purchased from Sigma-Aldrich (St Louis, MO, USA).