The qualitative study reported the presence of tannins, tertiary-amines, flavonoids, phenols, cynogenic glycosides, and alkaloids in the extract of AR.[23
In estimation of total phenolic content, when the concentration is increased, absorbance increased in both gallic acid and methanolic extract of AR. Relative standard deviation (RSD) of AR was superior (0.998) to that of gallic acid (0.966) indicating good linear correlation for AR . In probability theory and statistics, the RSD or (%RSD) is the absolute value of the coefficient of variation (CV). It is often expressed as a percentage. A similar term that is sometimes used is the relative variance, which is the square of the CV. In addition, the relative standard error is a measure of a statistical estimate's reliability obtained by dividing the standard error by the estimate, then multiplied by 100 to be expressed as a percentage. The RSD is widely used in analytical chemistry to express the precision and repeatability of an assay. RSD is a measure of precision (not accuracy). RSD is sometimes called CV and often is calculated as a percentage.
Absorbance comparisons of gallic acid and methanol extract of AR in different concentrations (μg/ml)
s = standard deviation, x = mean, RSD = s/x, as a percentage, (s/x) × 100
The RSD allows standard deviations of different measurements to be compared more meaningfully. For example, if one is measuring the concentration of two compounds A and B and the result is 0.5 (+/–) 0.4 ng/ml for compound A and 10 (+/–) 2 ng/ml for compound B, one may look at the standard deviation for compound A and say because it is lower (0.4 vs. 2) than for B, the measurement for A was more precise. Actually this is not the case. When the %RSD is used, the new values for compounds A and B are 0.5 (+/–) 80% and 10 (+/–) 20%, respectively; therefore, the measurement for compound B is more precise.
Estimation of total tannin content was found to be 2.82% w/w, indicating AR is a good source of tannin which is a well-known natural antioxidant.
Absorbance (at 765 nm) of gallic acid and methanol extract of AR in different concentrations (μg/ml)was linear for both methanolic extract of AR and ascorbic acid [, ].
Absorbance (at 765 nm) of gallic acid and methanol extract of AR in different concentrations (μg/ml)
Free radical scavenging activity on DPPH assay revealed that when the concentration increased percentage inhibition was increased, but there was no good linearity of both methanolic extract of AR and ascorbic acid [ and ]. In third-degree polynomial plotting, RSD was 1 for both AR and ascorbic acid [Figures and ]. EC50 for both test (AR) and standard were EC50 at 10–12 μg/ml with polynomial trend line extrapolated on graph [ and Figures , and ].
Free radical scavenging activity (DPPH assay) of ascorbic acid and methanol extract of AR
Free radical scavenging activity, % inhibition versus concentration for standard ascorbic acid (AA) and AR (polynomial plotting of second degree)
DPPH assay—polynomial plotting of third degree of Ascorbic acid
DPPH assay—polynomial plotting of third degreeof AR
EDTA and NBT assays revealed that when concentrations of methanol extract of AR and ascorbic acid increased, percentage inhibitions are also increased indicating good linear correlation. RSD of AR (0.976) found to be superior to that of ascorbic acid (0.925) [ and ].
Superoxide anion scavenging activity of ascorbic acid and methanol extract of AR
Superoxide radical scavenging activity, % inhibition versus concentration for standard ascorbic acid and test drug AR
The experiment on reducing power revealed that RSD of AR was 0.986, i.e., linear indicating good correlation between concentration of AR and reducing capacity. The ferric reducing/antioxidant power assay was used to measure the total antioxidant power of AR . Results showed that concentration tested antioxidant power and that the antioxidant capacity was strongly correlated (r = 0. 986) with the total phenolics content of the AR.
Reducing power of methanol extract of AR