Antioxidant activity and polyphenol content of Turkish thyme (Thymus vulgaris) monitored by liquid chromatography and tandem mass spectrometry

Figures & data

Table 1. Total phenolic and total flavonoid content of WETT and EETT (WETT: lyophilized water extract of thyme [Thymus vulgaris]; EETT: ethanol extract of thyme [Thymus vulgaris]).

	WETT	EETT
Total phenols*	256.0	158.0
Total flavonoids**	44.2	36.6

WETT: lyophilized water extract of thyme (Thymus vulgaris); EETT: ethanol extract of thyme (Thymus vulgaris).

*Determined as µg of gallic acid equivalent (GAE) in mg dried extracts.

**Determined as µg of quercetin equivalent (QE) in mg dried extracts.

Table 2. LC-MS/MS parameters of selected compounds and concentrations (mg/kg) of antioxidants in WETT and EETT.

No.	Compounds	Parent ion	Daughter ion	Collision energy (V)	Amount of antioxidants in the extracts (mg/kg)^a,b
					WET	EET
	Curcumin	367	216.4	10	–^a	–^a
1	Caffeic acid	179	134.0	11	131.2	81.4
2	Ferulic acid	193	177.5	10	232.3	232.3
3	Syringic acid	197	181.6	10	–^c	–^c
4	Ellagic acid	301	150.0	10	71.2	71.2
5	Quercetin	301	178.6	10	121.4	111.1
6	α-Tocopherol	429	162.6	20	–^c	–^c
7	Catechol	109	64.8	35	–^c	–^c
8	Pyrogallol	125	78.7	20	262.4	260.2
9	p-hydroxy benzoic acid	137	92.7	10	20.4	18.7
10	Vanillin	181	135.5	10	81.4	79.4
11	p-coumaric acid	163	118.7	10	151.4	164.6
12	Gallic acid	169	124.6	10	5150.2	1801.2
13	Ascorbic acid	175	114.0	12	30.1	30.1

WETT: lyophilized water extract of Turkish thyme (Thymus vulgaris); EETT: ethanol extract of Turkish thyme (Thymus vulgaris).

^aInternal standard.

^bThe uncertainty of the results calculated in accordance with Table 1.

^cThese values are below the limits of quantification.

Figure 1. Standard chromatogram of antioxidant phenolic acids using LC-MS/MS (mg/mL).

Figure 2. WETT and EETT chromotogram of antioxidants determined by LC-MS/MS. Samples three through eight were diluted for use in the linear range. WETT: lyophilized water extract of thyme (Thymus vulgaris); EETT: ethanol extract of thyme (Thymus vulgaris).

Table 3. Concentration required for 50% scavenging (IC₅₀) of DPPH• scavenging activity, ABTS^•+ scavenging activity of WETT, EETT and standard compounds, including BHA, BHT, α-tocopherol, and Trolox.

Compounds	DPPH• scavenging		ABTS^•+ scavenging
	IC50*	R^2	IC50*	R^2
BHA	12.9	0.9801	4.95^ψ	0.9990
BHT	31.2	0.8810	7.11	0.8246
Trolox	12.7	0.9343	6.11^ψ	0.8750
α-Tocopherol	13.6^ψ	0.8453	16.61^ψ	0.9820
WETT	13.4	0.9255	40.03	0.9246
EETT	12.1	0.9656	54.08	0.9914

WETT: lyophilized water extract of thyme (Thymus vulgaris); EETT: ethanol extract of thyme (Thymus vulgaris); DPPH: 1,1-diphenyl-2-picryl-hydrazyl free radical; ABTS^•+: 2,2´-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid; BHA: butylated hydroxyanisole; BHT: butylated hydroxytoluene.

*The values are expressed in μg/mL. Lower IC₅₀ values indicated an elevated radical scavenging activity.

^ψFrom Bursal et al.^[24]

Table 4. The total antioxidant activity, as measured using the thiocyanate method; the reducing ability, as measured using the Fe³⁺-Fe²⁺ transformation method; and the Cu²⁺ reducing ability, as measured using the CUPRAC method, of WETT, EETT, and standard compounds, including BHA, BHT, α-tocopherol, and Trolox at the same concentrations.

	Total antioxidant activity^ψ	Fe^3+-Fe^2+ reducing ability*		Cu^2+-Cu^+ reducing ability*
	λ 500	λ700	R^2	λ 450	R^2
BHA	83.3^φ	2.081	0.8593	0.565	0.8046
BHT	82.1^φ	1.657	0.9408	0.668	0.9085
Trolox	81.3^φ	1.861	0.9991	0.457	0.9655
α-Tocopherol	68.1^φ	1.465	0.9993	0.422	0.9666
WETT	51.7	2.021	0.8780	0.400	0.8699
EETT	64.4	1.888	0.9656	0.518	0.9489

WETT: lyophilized water extract of thyme (Thymus vulgaris); EETT: ethanol extract of thyme (Thymus vulgaris); BHA: butylated hydroxyanisole; BHT: butylated hydroxytoluene.

*The values are expressed as absorbance. A high absorbance indicates a high reducing power capacity.

^ψPercentage of inhibitory effect of 10 µg/mL concentration of WETT, EETT, and standard antioxidant molecules on linoleic acid emulsion peroxidation, as determined by the thiocyanate method.

^φFrom Gülçin et al.^[27]

Bursal, E.; Köksal, E.; Gülçin, İ.; Bilsel, G.; Gören, A.C. Antioxidant Activity and Polyphenol Content of Cherry Stem (Cerasus Avium L.) Determined by LC-MS/MS. Food Research International 2013, 51, 66–74.

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