(gm) Extract obtained (gm) Yield (%) Bauhinia scandens 1800 250 24.023 9.61 Table 2.Total phenolic and flavonoid contents of the ethanol extract of Bauhinia scandens Sample Total phenolic content (mg of gallic acid equivalent per g of dry extract) Total flavonoid content (mg of quercetin equivalent per g of dry extract) Bauhinia scandens 47.33 ±0.01 6.59 ±0.04 Data are represented as the mean ± SD, (n=2) 3.2.3 Determination of total flavonoid content The total flavonoid contents were calculated using the standard curve of quercetin (y = 0.003x + 0.109; R 2 = 0.915) and were expressed as quercetin equivalents (QE) per gram of the plant extract. Total flavonoid content was found 6.59 ±0.04 (mg QUE/gm) for EEBS. 3.3 Polyphenolic Compounds Analysis of EEBS The chromatographic separations of polyphenols in standard and ethanol extract are shown in Fig. 3.5 and 3.6 respectively. The content of each phenolic compound was calculated from the corresponding calibration curve and presented as the mean of five determinations as shown in Table 3. The experimental results indicated that ethanol extract of Bauhinia scandens contained a high concentration of gallic acid, ellagic acid and rosmarinic acid (215.39, 72.24 & 50.96 mg/100 g of dry extract, respectively). Vanillin was also detected at moderate concentration in the ethanol extract of Bauhinia scandens (39.85 mg/100 g of dry extract). Vanillic acid, and syringic acid were also detected at lower concentration (12.34 & 17.15 mg/100 g of dry extract, respectively). DPPH radical scavenging is a widely used method to evaluate the free radical scavenging activity of compounds or antioxidant capacity of plant extracts . It is considered as a basic and rapid screening method which demonstrated the antioxidant effect by decrease in the absorbance at 517 nm . DPPH is a stable nitrogen-centered free radical, the color of which changes from violet to yellow upon reduction by either the process of hydrogen or electron donation . The greater the decolorizing action, the higher the antioxidant activity, and is reflected by lower IC 50 value. Substances which are able to perform this reaction can be considered as antioxidants and, therefore, radical scavengers. In the present study, all the plant extracts showed dose dependent scavenging of DPPH free radicals in a way similar to that of the standard antioxidant ascorbic acid. However, the EEBS exhibited good antioxidant potency (IC50= 13.5 μg/ml) which was close to antioxidant effect of ascorbic acid (IC50= 8.25 μg/ml). Presence of total phenol content and flavonoid in the plant extracts may be a reason for this DPPH- scavenging activity. So, present study showed that the extracts have the proton-donating ability due to presence of phenolics and could serve as free radical inhibitors or scavengers, acting possibly as primary antioxidants . Table 3. Contents of polyphenolic compounds in the EEBS (n=5) Polyphenolic compound EEBS Content (mg/100 g of dry extract) % RSD GA VA SA VL EA RA 215.39 12.34 17.15 39.85 72.24 50.96 1.97 0.42 0.33 0.03 0.08 0.05 Presence of polyphenols has been reported to be responsible for the antioxidant activity in plant extracts . Phenolic constituents react with active oxygen radicals such as hydroxyl radical, superoxide anion radical and lipid peroxyl radical . Antioxidative properties of polyphenols arise
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