Comparative study on the effect of extraction solvent on total phenol, flavonoid content, antioxidant and antimicrobial properties of red onion (Allium cepa)

Table 3
Inhibition zone diameter (mm, mean ± SD) of red onion skin extracts against S. aureus 
Values in a row with same lower case letters and values in columns with same upper case letters are not statistically different (p > 0.05)
** And * show a significant difference at 1% and 5% probability level, respectively
Extract
Concentrations (μg/mL)
6.25
12.5
25
50
100
200
400
Aqueous
7.67 ± 0.58f (BC)
8.67 ± 0.58ef (ABC)
9.00 ± 0.00ef(BC)
9.67 ± 0.58de(AB) 10.67 ± 0.58cd(AB) 11.67 ± 1.53bc(C)
13.00 ± 1.00b(B)
Ethanol
7.00 ± 0.00 g(C)
8.00 ± 0.00ef (ABC)
8.33 ± 1.00e(C)
8.67 ± 0.58ef(B)
9.33 ± 0.58d(B)
12.00 ± 1.00c(BC)
14.00 ± 2.00b(B)
Methanol
7.33 ± 0.58f (C)
7.67 ± 0.58ef(C)
8.67 ± 0.58de(C)
8.33 ± 0.58def(B)
9.00 ± 1.00 cd(B)
10.00 ± 0.00c(C)
11.67 ± 0.58b(B)
n-butanol
8.33 ± 0.58d(AB)
9.33 ± 0.58d(A)
10.00 ± 0.00d(AB)
10.33 ± 0.58d(A)
12.67 ± 2.52c(A)
14.00 ± 1.73c(AB)
16.33 ± 1.53b(A)
Ethyl acetate
8.67 ± 0.58e (A)
9.00 ± 1.00de(AB)
10.33 ± 1.16de(A)
10.67 ± 1.16d(A)
13.33 ± 1.53c(A)
14.33 ± 0.58c(A)
17.67 ± 0.57b(A)
F tests
5.37*
3.58*
5.58*
5.81*
5.48*
7.18**
11.21**
Table 4
Inhibition zone diameter (mm, mean ± SD) of red onion skin extracts against E. coli 
Values in a row with same lower case letters and values in columns with same upper case letters are not statistically different (p > 0.05). n.s 
shows that there is no significant difference
Extract
Concentrations (μg/mL)
6.25
12.5
25
50
100
200
400
Aqueous
8.00 ± 1.00c(A)
8.67 ± 1.16c(A)
9.00 ± 1.00bc(A)
8.67 ± 1.53c(A)
9.00 ± 1.00bc(A)
9.67 ± 1.53bc(A)
11.00 ± 1.00b(A)
Ethanol
7.00 ± 0.00d(A)
7.33 ± 0.58d(A)
7.67 ± 0.58 cd(B)
8.00 ± 0.00d(A)
8.33 ± 1.16 cd(A)
9.67 ± 1.16bc(A)
10.33 ± 1.16b(A)
Methanol
7.00 ± 0.00e(A)
7.67 ± 0.58de(A)
8.00 ± 0.00 cd(AB)
8.00 ± 0.00 cd(A)
8.67 ± 0.58c(A)
9.33 ± 0.58b(A)
10.33 ± 0.58b(A)
n-butanol
7.67 ± 0.58d(A)
8.33 ± 0.58 cd(A)
8.67 ± 0.58 cd(AB)
9.33 ± 0.58c(A)
9.67 ± 1.58c(A)
11.33 ± 1.16b(A)
12.33 ± 1.53b(A)
Ethyl acetate
7.00 ± 0.00f(A)
7.33 ± 0.58ef(A)
8.00 ± 0.00de(AB)
8.33 ± 0.58d(A)
8.367 ± 0.58 cd(A)
9.33 ± 0.58c(A)
10.33 ± 0.58b(A)
F tests
2.50n.s
2.06n.s
2.70n.s
1.17n.s
1.15n.s
1.85n.s
2.12n.s
Table 5
Inhibition zone diameter (mm, mean ± SD) of red onion skin extracts against S. Typhi
Values in a row with same lower case letters and values in columns with same upper case letters are not statistically different (p > 0.05). n.s 
shows that there is no significant difference
** And *show a significant difference at 1% and 5% probability level, respectively
Extract
Concentrations (μg/mL)
6.25
12.5
25
50
100
200
400
Aqueous
7.00 ± 1.00f(B)
8.00 ± 1.00ef(B)
9.00 ± 1.00de(B)
9.33 ± 1.16cde(B)
9.67 ± 0.58 cd(A)
10.67 ± 0.58bc(A)
11.67 ± 0.58b(A)
Ethanol
6.67 ± 0.58f(B)
8.00 ± 0.00e(B)
9.00 ± 0.00de(B)
9.33 ± 0.58 cd(B)
10.00 ± 0.00 cd(A)
10.33 ± 0.58c(A)
12.67 ± 1.16b(A)
Methanol
7.00 ± 1.00d(B)
7.33 ± 0.58d(B)
7.33 ± 0.58d(C)
8.00 ± 0.00d(C)
9.33 ± 0.58c(A)
10.33 ± 0.58bc(A)
11.33 ± 0.58b(A)
n-butanol
8.67 ± 0.58d(A)
9.67 ± 0.58 cd(A)
10.33 ± 0.58c(A)
9.67 ± 0.58 cd(AB) 10.33 ± 0.58c(A)
10.67 ± 0.58bc(A)
11.67 ± 0.58b(A)
Ethyl acetate
9.00 ± 0.00f(A)
9.67 ± 0.58ef(A)
10.33 ± 0.58de(A)
10.67 ± 0.58de(A)
10.33 ± 0.58de(A)
11.33 ± 0.58 cd(A)
12.00 ± 1.00b(A)
F tests
6.56**
8.58**
11.50**
5.86*
2.12n.s
1.50n.s
1.15n.s

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3586
S. Khalili et al.
1 3
mL of ethanolic extracts represented a greater inhibitory 
effect on S. Typhi and A. niger than aqueous extract. They 
also stated that the aqueous extract had no inhibitory effect 
on the fungus. Differences in Plant age, geographical area 
of plant growth, solvent type, the method of drying and 
extraction methods may be the reasons for the difference 
between the present results and those obtained by previous 
researches. Researchers also recognized that pharmaco-
logical performance of the extracts such as antimicrobial 
Table 6
Inhibition zone diameter (mm, mean ± SD) of red onion skin extracts against A. niger 
Values in a row with same lower case letters and values in columns with same upper case letters are not statistically different (p > 0.05)
**Shows a significant difference at 1% probability level
extract
Concentrations (μg/mL)
6.25
12.5
25
50
100
200
400
Aqueous
7.00 ± 1.00f (C) 8.00 ± 1.00ef (C) 9.33 ± 0.58e (B) 9.67 ± 0.58e (C) 12.67 ± 0.58d (D) 15.00 ± 1.00c (B) 17.33 ± 0.58b(C)
Ethanol
8.33 ± 0.58e (B) 8.67 ± 0.58e (BC) 10.33 ± 0.58de 
(B)
12.00 ± 1.00d (B) 14.67 ± 0.58c 
(BC)
21.00 ± 1.00b (A) 21.67 ± 1.16a(A)
Methanol
8.33 ± 0.58f (B) 9.33 ± 0.58ef (B) 10.67 ± 0.58e (B) 11.33 ± 0.58e (B) 14.00 ± 1.00d 
(CD)
16.33 ± 1.58c (B) 19.00 ± 1.00b(c)
n-butanol
7.67 ± 0.58f (BC) 9.33 ± 0.58ef (B) 10.67 ± 0.58de 
(B)
12.67 ± 1.16d (B) 16.33 ± 1.53c (B) 22.00 ± 1.00b (A) 24.33 ± 0.58a(AB)
Ethyl acetate 10.33 ± 0.58e (A) 11.67 ± 0.58de 
(A)
13.67 ± 1.53 cd 
(A)
15.00 ± 1.00c (A) 19.00 ± 1.00b (A) 22.33 ± 1.53a(A) 23.67 ± 1.16a(B)
F tests
10.00**
12.29**
10.77**
14.29**
17.83**
30.88**
45.38**