Physicochemical characterization and antibacterial activity of the leaf oil of Crotalaria pallida Aiton

Peer review under responsibility of Taibah University.

Figures & data

Fig. 1 IR of fatty acids of leaf (C. pallida) oil.

Fig. 2 Gas-chromatogram of fatty acid methyl esters of leaf oil of C. pallida.

Table 1 Some properties of the leaf oil of C. pallida.

Parameters	Properties
Physical state at room temperature	Semi-solid
Colour	Dark green
Odour	Pleasant
Total oil content (g/100 g)	8.60 ± 0.20
Density (g/ml)	1.356 ± 0.003
Specific gravity	1.240 ± 0.002
Acid value (mg KOH/g)	19.63 ± 0.22
Saponification value (mg KOH)	109.08 ± 2.87
Inhibition against bacteria	Zone diameter (mm)
Bacillus subtilis	15
Escherichia coli	18
Acinetobacter junii	18

Table 2 Fatty acid composition of the leaf oil of C. pallida by GC–MS.

Peak	Retention time (in min)	Molecular ion peak (M^+)	Name of the fatty acid methyl ester	Relative percentage^a
1	14.764	200.29	Undecanoic acid (C11:0)	0.11 ± 0.01
2	15.040	214.32	Lauric acid (C12:0)	0.07 ± 0.01
3	15.758	–	Unidentified	0.08 ± 0.00
4	16.494	–	Unidentified	0.10 ± 0.01
5	17.279	228.34	Tridecanoic acid (C13:0)	0.29 ± 0.02
6	17.997	242.37	Myristic acid (C14:0)	0.39 ± 0.02
7	19.585	258.40	Pentadecanoic acid (C15:0)	0.40 ± 0.04
8	20.076	–	Unidentified	0.89 ± 0.03
9	20.717	–	Unidentified	1.77 ± 0.11
10	21.276	270.42	Palmitic acid (C16:0)	24.47 ± 0.22
11	22.215	268.41	7-Hexadecanoic acid (C16:1)	1.00 ± 0.01
12	22.840	284.45	Heptadecanoic acid (C17:0)	0.55 ± 0.03
13	23.458	–	Unidentified	0.09 ± 0.01
14	23.864	–	Unidentified	0.04 ± 00
15	24.419	298.48	Stearic acid (C18:0)	4.84 ± 0.05
16	25.341	296.46	Oleic acid (C18:1)	4.60 ± 0.11
17	26.433	266.40	7,10-Hexadecadienoic acid (C16:2)	0.09 ± 0.01
18	26.772	294.45	Linoleic acid (C18:2)	13.50 ± 0.12
19	27.692	–	Unidentified	0.01 ± 00
20	27.907	326.53	Eicosanoic acid (C20:0)	3.61 ± 0.10
21	28.412	292.40	Linolenic acid (C18:3)	34.06 ± 0.23
22	29.309	340.56	Heneicasanoic acid (C21:0)	0.15 ± 0.02
23	30.597	354.58	Behenic acid (C22:0)	3.67 ± 0.11
24	31.409	–	Unidentified	0.05 ± 0.00
25	32.019	368.60	Tricosanoic acid (C23:0)	0.21 ± 0.02
26	33.300	382.64	Tetracosanoic acid (C24:0)	4.08 ± 0.08
27	34.787	–	Unidentified	0.15 ± 0.02
28	36.219	410.69	Hexacosanoic acid (C26:0)	0.73 ± 0.01
			Unsaturated fatty acids	53.25
			Saturated fatty acids	43.57
			Unidentified	3.18
			Unsaturated fatty acids:saturated fatty acids	1.22:1

a Values are means ± S.D; n = 3

Table 3 MIC of the Fatty acid constituents of the leaf oil of C. pallida against some bacteria.

Antibacterial substances	Test organisms
	MIC (μg/ml)
	Bacillus subtilis	Escherichia coli	Acinetobacter junii
Leaf oil	80 ± 0.58	10 ± 0.14	10 ± 0.25
Tetracycline (control)	1.5 ± 0.04	2.5 ± 0.05	5 ± 0.08
Ampicillin (control)	1 ± 0.02	3 ± 0.04	25 ± 0.11