Antibacterial and antifungal metal based triazole Schiff bases

Figures & data

Figure 1.  Triazole compounds.

Scheme 1.  Preparation of the ligands L¹–L⁴.

Scheme 2.  Proposed structure of the metal(II) complexes.

Figure 2.  Proposed mass fragmentation pattern of L¹.

Table 1.  Antibacterial bioassay (concentration used 1 mg/mL of DMSO) of ligands L¹–L4 and the metal(II) complexes 1–16.

Compounds	Zone of inhibition (mm)
	Gram-negative			Gram-positive			SA	Average
	(a)	(b)	(c)	(d)	(e)	(f)
L^1	14	12	15	14	13	15	1.17	13.8
L^2	14	13	15	15	14	16	1.05	14.5
L^3	13	13	14	16	14	15	1.17	14.2
L^4	16	12	17	14	13	16	1.97	14.7
1	18	17	17	19	16	19	1.21	17.7
2	19	13	19	16	19	21	2.86	17.8
3	16	18	18	19	16	17	1.21	17.3
4	17	16	20	17	17	18	1.38	17.5
5	16	17	18	18	18	24	2.81	18.5
6	19	16	20	17	17	19	1.55	18.0
7	17	18	21	17	16	18	1.72	17.8
8	18	20	19	16	17	24	2.83	18.6
9	14	19	15	21	16	18	2.64	17.2
10	19	17	19	18	16	19	1.26	18.0
11	16	17	15	20	17	18	1.72	17.2
12	18	17	18	23	18	19	2.14	18.8
13	19	17	20	16	18	19	1.47	18.2
14	19	16	18	17	16	24	3.01	18.0
15	21	13	20	18	17	17	2.80	17.7
16	19	18	22	16	14	20	2.86	18.2
A	10	10	12	10	11	11	0.82	10.7
SD	26	24	32	28	27	29	2.73	27.7

Average of Ligands L¹–L⁴ = 14.3 mm; average of Complexes 1–16 = 17.9 mm. Activity <10 = weak; >10 = moderate; > 16 = Significant. (a), E. coli; (b), S. sonnei; (c), P. aeruginosa; (d), S. typhi; (e), S. aureus; (f), B. subtilis; A, 3-Amino-5-methylthio-1H-1,2,4-triazole;

SD, standard drug (Ampicillin).

SA = Statistical Analysis.

Table 2.  Antifungal bioassay (concentration used 200 µg/mL) of ligands L¹–L⁴ and the metal(II) complexes 1–16.

Compounds	% Inhibition (mm)
	(a)	(b)	(c)	(d)	(e)	(f)	SA	Average
L^1	35	61	57	39	18	46	15.70	42.7
L^2	28	43	60	33	57	48	12.76	44.8
L^3	47	40	38	19	54	67	16.21	44.2
L^4	51	27	59	39	57	43	12.11	46.0
1	39	65	60	44	19	50	16.46	46.2
2	37	62	59	40	22	48	14.91	44.7
3	40	57	62	43	23	49	13.85	45.7
4	35	66	58	45	25	39	15.13	44.6
5	34	47	64	37	60	50	11.99	48.7
6	31	45	62	33	58	52	12.85	47.2
7	29	46	63	30	62	49	14.81	46.5
8	35	43	61	35	59	51	11.48	47.3
	51	44	39	23	59	74	17.48	48.3
10	55	39	43	21	50	69	16.18	46.2
11	47	42	40	24	56	76	17.45	47.5
12	53	43	45	20	57	75	18.16	48.8
13	54	30	64	43	65	48	13.32	50.7
14	57	29	56	44	59	44	11.47	48.2
15	52	33	62	42	60	40	11.66	48.2
16	55	31	65	37	62	49	13.60	49.8
SD	A	B	C	D	E	F	–	–

Average of ligands L¹–L⁴ = 44.4%; Average of complexes 1–16 = 47.4%.

(a), T. longifucus; (b), C. albicans; (c) A. flavus; (d), M. canis; (e), F. Solani; (f), C. Glabrata; SD, standard drugs MIC µg/mL; A, Miconazole (70 µg/mL:1.6822 × 10⁻⁷ M/mL); B, Miconazole (110.8 µg/mL:2.6626 × 10⁻⁷ M/mL); C, Amphotericin B (20 µg/mL:2.1642 × 10⁻⁸ M/mL), D, Miconazole (98.4 µg/mL:2.3647 × 10⁻⁷ M/mL); E, Miconazole (73.25 µg/mL: 1.7603 ×10⁻⁷ M/mL); F, Miconazole (110.8 µg/mL: 2.66266 × 10⁻⁷ M/mL). SA, statistical analysis.

Table 3.  Minimum inhibitory concentration (µg/mL) of the selected compounds 5, 8, 12, 14 and 15 against selected bacteria

Bacterial strains	(5)	(8)	(12)	(14)	(15)
Gram negative
E. coli	–	–	–	–	79.46
S. sonnei	–	58.62	–	–	–
S. typhi	–	–	60.62	–	–
Gram positive
B. subtilis	90.33	67.2	–	70.75	–