In this report, we have included 49 Bangladeshi medicinal plants representing 36 families and claimed to have strong antioxidant properties. The families are Acanthaceae, Anacardiaceae, Annonaceae, Apocynaceae, Asclepiadaceae, Asteraceae, Bignoniaceae, Caesalpinaeceae, Combertaceae, Dipterocarpaceae, Ebenaceae, Euphorbiaceae, Gentianaceae, Labiatae, Leguminosae, Liliaceae, Loranthaceae, Lythraceae, Manispermaceae, Meliaceae, Moraceae, Moringaceae, Myristaceae, Nyctaginaceae, Piperaceae, Ranunculaceae, Rhizophoraceae, Rubiaceae, Sapotaceae, Sonneratiaceae, Sterculiaceae, Umbelliferae, Verbenaceae, Vitaceae, Zingiberaceae, and Zygophyllaceae.
Numerous procedures have been used for the determination of both the in vivo and in vitro antioxidant activity of either crude extracts and/or pure compounds of plant origin. Among them, ferric reducing/antioxidant power (FRAP) assay, total radical-trapping antioxidant potential (TRAP) assay, β-carotene–linoleic acid model system (β-CLAMS), oxygen radical absorption capacity (ORAC) method, thiobarbituric acid reactive substance (TBARS) method, trolox equivalent antioxidant capacity (TEAC) method, photo chemiluminescence (PCL) method, 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) assay, and superoxide anion radical scavenging, hydrogen peroxide scavenging, and metal ion chelating activities are widely used (Davalos et al., 2004; Tsao et al., 2004). The plants included in this report were investigated by either the DPPH assay or by superoxide anion free radical scavenging assay. The DPPH assay has been widely used to evaluate the free radical scavenging capacity of antioxidants (BrandWillams et al., 1995; Espin et al., 2000; Yu et al., 2001). The method is considered to be a fast screening procedure for the determination of antioxidant activity of plant extracts. The method involves determination of the antiradical power of an antioxidant by measurement of the decrease in the absorbance of DPPH radical at 517 nm (Matthaus et al., 2002). To determine superoxide-scavenging activity, two different assays were used: the enzymatic method with cytochrome C (McCord et al., 1969) and nonenzymatic method with nitroblue tetrazolium (NBT) (Zhang et al., 1990). With cytochrome C method, superoxide anions were generated by a xanthine and xanthine oxidase system. The superoxide scavenging activity was calculated by measuring the reduction rate of ferricytochrome C at 550 nm. With the NBT method, superoxide was generated by potassium peroxide. The inhibition rate was calculated by measuring the amount of the formazan that was reduced from NBT by superoxide at 560 nm.