Antioxidant Activity
DPPH Free radical scavenging activity
In the DPPH free radical scavenging assay, methanol extract showed concentration dependent inhibition of the free radicals as shown in Figure 1. Here the methanol extract of N. capensis showed significant activity. At conc. 31.25, 62.5, 125, 250, 500ug/ml, the percentages of inhibition of ascorbic acid were 38.37, 53.57, 73.78, 81.08 and 92.16 whereas the percentages of N. capensis were 25.54, 43.64, 57.83, 72.83 and 87.16 respectively. IC50 of Ascorbic acid was 14.84 µg/ml whereas N. capensis was 130.94 µg/ml.
Table 1: Percentage of DPPH radical scavenging activity of ascorbic acid.
Concentration (µg/ml)
|
Absorbance
|
% of Scavenging
|
IC50 (µg/ml)
|
500
|
0.058
|
92.16
|
14.84
|
250
|
0.140
|
81.08
|
|
125
|
0.194
|
73.78
|
62.5
|
0.345
|
53.57
|
31.25
|
0.456
|
38.37
|
Table 2: Percentage of DPPH radical scavenging activity of N. Capensis.
Concentration (µg/ml)
|
Absorbance
|
% of Scavenging
|
IC50 (µg/ml)
|
500
|
0.095
|
87.16
|
|
250
|
0.201
|
72.83
|
|
125
|
0.312
|
57.83
|
130.94
|
62.5
|
0.417
|
43.64
|
|
31.25
|
0.561
|
25.54
|
|
Ferric reducing capacity
The reducing capacity of a compound indicates its potential antioxidant activity. Figure 2 shows the dose response curves for the reducing power of methanol extract of N. capensis. At conc. 62.5, 125, 250, 500, 1000 ug/ml, the absorbances of Ascorbic acid were 0.65, 1.12, 1.45, 1.78 and
1.89 respectively. In case of N. capensis, the absorbances were 0.46, 0.75, 1.04, 1.27 and 1.50 respectively. The extract displayed a concentration dependent increase in reducing power. The reducing power increased with increasing amount of the extracts. Higher absorbance of the reaction mixture indicates a higher reducing power. Thus, the present results showed that higher reducing power was evident in methanol extract of N. capensis.
Table 3: Reducing power of N. Capensis with standard Ascorbic acid.
Concentration (µg/ml)
|
Ascorbic acid
|
N. Capensis
|
1000
|
1.89
|
1.50
|
500
|
1.78
|
1.27
|
250
|
1.45
|
1.04
|
125
|
1.12
|
0.75
|
62.5
|
0.65
|
0.46
|
Determination of total phenolic content
Total phenolic content was estimated by gallic acid (Figure 3) and expressed as milligrams of gallic acid equivalent (GAE). The methanol extracts of N. capensis contained a considerable amount of phenolic contents of 215±7 of GAE/g of extract (Table 4).
Table 4: Total phenol content of N. Capensis with necessary data.
Concentration(µg/ml)
|
Absorbance
|
m (gm)
|
c (mg/ml)
|
A= (c×v)/m
|
Mean (mg/g)
|
200
|
0.295
|
0.0002
|
0.043
|
215
|
|
200
|
0.305
|
0.0002
|
0.044
|
222
|
215±7
|
200
|
0.285
|
0.0002
|
0.041
|
208
|
|
Determination of total flavonoid content
The total flavonoid content of the N. capensis leaves were estimated by using aluminium chloride colorimetric technique and found that the N. capensis extract contained significant amount of flavonoid contents of 184.75±6.78 of GAE/g of extract. (Table: 5).
Table 5: Total flavonoid content of N. Capensis with necessary data.
Concentration(µg/ml)
|
Absorbance
|
m (gm)
|
c (mg/ml)
|
A= (c×v)/m
|
Mean (mg/g)
|
200
|
0.348
|
0.0002
|
0.035
|
177.85
|
|
200
|
0.358
|
0.0002
|
0.037
|
185
|
184.75±6.78
|
200
|
0.367
|
0.0002
|
0.038
|
191.42
|
|