In vitro antibacterial, antifungal and cytotoxic activities of some triazole Schiff bases and their oxovanadium(IV) complexes

Figures & data

Scheme 1.  Preparation of triazole Schiff base ligands (L¹)–(L⁶) and their oxovanadium(IV) complexes (1)–(6).

Table 1.  Physical and analytical data of the oxovanadium(IV) complexes.

No.	Structure	MW (g/mole)	M.P (dec.)	Yield (%)	Found (calculated) %
		Formula	(°C)	[Colour]	C	H	N	V
(1)	[VO(L^1-H)2]	[471.33]	229–232	81	45.84	3.41	29.67	10.77
		C18H16N10O3V		[Sea green]	(45.87)	(3.42)	(29.72)	(10.81)
(2)	[VO(L^2-H)2]	[531.38]	252–255	78	45.19	3.76	26.32	9.56
		C20H20N10O5V		[Deep green]	(45.25)	(3.79)	(26.39)	(9.59)
(3)	[VO(L^3-H)2]	[540.22]	251–253	80	39.98	2.58	25.90	9.41
		C18H14Cl2N10O3V		[Light green]	(39.94)	(2.61)	(25.93)	(9.43)
(4)	[VO(L^4-H)2]	[629.12]	243–245	82	34.32	2.23	22.23	8.07
		C18H14Br2N10O3V		[Sea green]	(34.36)	(2.24)	(22.26)	(8.10)
(5)	[VO(L^5-H)2]	[723.12]	236–239	79	29.86	1.93	19.35	7.02
		C18H14I2N10O3V		[Deep green]	(29.90)	(1.95)	(19.37)	(7.04)
(6)	[VO(L^6-H)2]	[561.32]	272–275	72	38.47	2.53	29.90	9.05
		C18H14N12O7V		[Green]	(38.51)	(2.51)	(19.95)	(9.08)

Table 2.  Physical and spectral data of oxovanadium(IV) complexes.

No.	ΩM (Ω^−1 cm^2 mol^−1)	B.M (µeff)	λmax (cm^−1)	IR (cm^−1)
(1)	35.9	1.69	13435 (744), 18239 (548), 26226 (381), 37272 (268)	1618 (C=N), 1377 (C-O), 960 (V=O), 525 (V-O), 423 (V-N)
(2)	42.3	1.71	13542 (738), 18723 (534), 26189 (382), 37155 (269)	1616 (C=N), 1376 (C-O), 958 (V=O), 519 (V-O), 425 (V-N)
(3)	39.6	1.77	13536 (738), 18641 (536), 26355 (379), 37346 (268)	1619 (C=N), 1378 (C-O), 967 (V=O), 529 (V-O), 433 (V-N)
(4)	42.9	1.70	13478 (742), 18504 (540), 26312 (378), 37272 (268)	1620 (C=N), 1382 (C-O), 959 (V=O), 523 (V-O),432 (V-N)
(5)	41.3	1.67	13458 (743), 18519 (540), 26378 (379), 37189 (269)	1622 (C=N), 1383 (C-O), 961 (V=O), 523 (V-O), 429 (V-N)
(6)	37.6	1.67	13567 (737), 18728 (534), 26316 (380), 37409 (267)	1626 (C=N), 1386 (C-O), 970 (V=O), 529 (V-O), 438 (V-N)

Table 3.  Antibacterial activity (concentration used 1 mg/mL of DMSO) of triazole Schiff bases and oxovanadium(IV) complexes.

Bacteria	Compounds [zone of inhibition (mm)]
	(L^1)	(L^2)	(L^3)	(L^4)	(L^5)	(L^6)	(1)	(2)	(3)	(4)	(5)	(6)	(A)	SD
Gram-negative
(a)	15	14	17	16	17	18	20	18	24	19	26	24	10	29
(b)	11	12	18	13	18	19	17	17	25	16	18	22	12	31
(c)	17	09	15	17	17	18	19	16	18	26	19	25	11	30
(d)	11	13	12	16	18	19	16	21	19	22	20	24	10	29
Gram-positive
(e)	11	12	18	12	17	16	16	19	22	16	21	22	08	26
(f)	17	14	16	11	20	19	21	18	20	17	16	23	09	28
SA	3.01	1.86	2.28	2.48	1.17	1.17	2.14	1.72	2.80	3.98	3.41	1.21	1.41	1.72
Average of bacterial strains
	13.3	11.7	16	13	16.7	18.2	17.5	17.8	21.5	19.3	20	23.3	10	28.8

(a) = E. coli, (b) = S. flexneri, (c) = P. aeruginosa, (d) = S. typhi (e) = S. aureus, (f) = B. Subtilis; <10 = weak; 11–15 = moderate; 16 and above = significant; (A), simple triazole; SD, standard drug = Imipenum; SA, Statistical analysis.

Table 4.  Antifungal activity (concentration used 200 µg/mL) of triazole Schiff bases and oxovanadium(IV) complexes.

Organism	Compounds [% Inhibition]
	(L^1)	(L^2)	(L^3)	(L^4)	(L^5)	(L^6)	(1)	(2)	(3)	(4)	(5)	(6)	SD
(a)	46	35	58	42	26	61	56	43	75	59	45	81	A
(b)	58	41	46	56	38	54	67	55	62	77	56	70	B
(c)	43	00	62	23	42	56	38	34	80	38	63	63	C
(d)	00	56	43	54	55	60	40	70	57	43	69	78	D
(e)	37	34	37	35	22	48	54	49	54	43	38	62	E
(f)	49	46	55	48	39	45	36	62	73	64	54	57	F
SA	22	18	19	18	16	19	17	16	19	16	70	70
Average of fungal strains
	38.8	34.7	50.2	43	37	53.2	48.5	52.2	66.8	54	47	68.5

(a) = T. longifusus (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 5.  Minimum inhibitory concentration (M/mL) of the selected compounds (3), (4), (5) and (6) against selected bacteria.

Microorganisms	MIC (M/mL)^a
	(3)	(4)	(5)	(6)
Gram-negative
E. coli	3.210 × 10^−4	ND	2.125 × 10^−5	5.413 × 10^−4
S. flexneri	4.713 × 10^−3	ND	ND	ND
P. aeruginosa	ND	4.543 × 10^−4	ND	2.832 × 10^−3
S. typhi	ND	ND	ND	4.653 × 10^−6
Gram-positive
S. aureus	4.339 × 10^−5	ND	7.129 × 10^−4	2.199 × 10^−7
B. subtilis	ND	ND	ND	5.715 × 10^−5

^aEach compound was measured three times, with a standard deviation (SD) less than 10% in all the cases. ND is not determined at tested concentrations.

Table 6.  Brine shrimp bioassay data of triazole Schiff bases (L¹)–(L⁶) and oxovanadium(IV) complexes (1)–(6).

Ligands/complexes	LD50 (M/mL)
(L^1)	>4.315 × 10^− 4
(L^2)	>3.926 × 10 ^− 2
(L^3)	>2.181 × 10^− 3
(L^4)	>4.116 × 10^− 2
(L^5)	>2.835 × 10^− 4
(L^6)	>3.825 × 10 ^− 3
(1)	>3.456 × 10^− 3
(2)	>2.632 × 10^− 3
(3)	4.116 × 10^− 5
(4)	>2.236 × 10^− 2
(5)	>3.356 × 10^− 4
(6)	5.615 × 10^− 4