Phenolic composition as measured by liquid chromatography/mass spectrometry and biological properties of Tunisian barley

Figures & data

Figure 1. Total phenolic content (TPC) in four Tunisian barley varieties. Means (expressed as mg GAE⋅g⁻¹ DW) of three replicates followed by at least one same letter are not significantly different at p < 0.05.

Table 1. Antioxidant activities of seed extracts of Tunisian barley varieties.

	ABTS (IC50 µg⋅ml^−1)	FRAP (IC50 µg⋅ml^−1)	β-Carotene (IC50 µg⋅ml^−1)	DPPH (IC50 µg⋅ml^−1)	O2^.- (IC50 µg⋅ml^−1)
Manel	170.29 ± 0.69^d	342.33 ± 1.68^c	91.20 ± 1.11^d	85.71 ± 0.55^d	111.40 ± 1.56^c
Swihli	96.62 ± 0.33^a	169.2 ± 1.22^a	52.59 ± 0.43^a	44.83 ± 0.35^a	62.62 ± 0.46^a
Faiz	160.26 ± 0.68^c	440.63 ± 7.1^d	100.50 ± 0.2^c	80.36 ± 0.05^c	110.15 ± 0.37^c
Rihane	100.66 ± 0.47^b	184.6 ± 1.68^b	70.65 ± 0.15^b	58.08 ± 3.5^b	80.42 ± 0.06^b

All activities were expressed as IC₅₀ (µg⋅ml⁻¹). Means from three replicates followed by at least one same letter are not significantly different at p < 0.05.

ABTS: 2,2ʹ-Azinobis(3-ethylbenzothiazo-line-6-sulphonic acid) diammonium salt; FRAP: ferric reducing/antioxidant power; DPPH: 1,1-difenyl-2-picrylhydrazyl; O2.⁻: superoxide anion radical.

Figure 2. Antimicrobial properties of barley seed extracts. In vitro evaluation of the antibacterial activity of various barley extracts against five pathogenic microorganisms expressed as percentage of growth inhibition. Means of three replicates followed by at least one same letter are not significantly different at p < 0.05.

Table 2. LC-DAD-ESI-MS determination of phenolic compounds in four Tunisian barley varieties.

Phenolic composition (µg⋅g^−1 DW)	Faiz	Rihane	Swihli	Manel
GC-GC-C	57^c	98.38^a	76.89^b	37.02^d
Catechin-3-glucose	17.63^b	48.2^a	48.81^a	15.39^c
Procyanidin B3	458.82^c	536.32^b	601.3^a	232.12^d
Catechin	98.83^a	97.81^a	92.88^a	92.1^a
Vanillic acid	0.464^b	3.27^a	2.95^a	ND
Hydroferuloyl glucose	0.464^c	2.8^b	4.75^a	ND
Synapoyl hexose	<LOQ	<LOQ	<LOQ	<LOQ
TPC	603.20^c	786.78^b	827.62^a	376.63^d

Different letters in the same line indicate significant differences (p < 0.05).

GC-GC-C: gallocatechin–gallocatechin–catechin; TPC: total phenolic content; LOQ: limit of quantification; DW: dry weight; ND: not detected.

Table 3. Pearson’s correlation test between TPC and various antioxidant assays evaluation indices and among the different methods used to evaluate antioxidant activity.

	TPC	ABTS	FRAP	β-Carotene	DPPH	O2^.-
TPC	1
ABTS	−0.9716	1
FRAP	−0.8509	0.9133	1
β-Carotene	−0.9230	0.9115	0.9469	1
DPPH	−0.9877	0.9670	0.8809	0.9522	1
O2^.-	−0.9797	0.9602	0.9119	0.9790	0.9918	1

Values in bold are different from 0 with a significance level alpha = 0.05.

TPC: total phenolic content; ABTS: 2,2ʹ-Azinobis(3-ethylbenzothiazo-line-6-sulphonic acid) diammonium salt; FRAP: ferric reducing/antioxidant power; DPPH: 1,1-difenyl-2-picrylhydrazyl; O2.⁻: superoxide anion radical.

Figure 3. HPLC-DAD-ESI-MS chromatograms of phenolic compounds in four Tunisian barley varieties. The chromatogram was obtained for the maximum wavelength at each time point. 1: GC-GC-C; 2: catechin-3-glucose; 3: procyanidin B3; 4: catechin; 5: vanillic acid; 6: hydroferuloyl glucose; 7: synapoyl hexose.

Figure 4. Contents in flavanols (a) and phenolic acids (b) as a function of barley variety.

Figure 5. Proportion (%) of procyanidin B3 compared to the rest of flavanols and phenolic acid family in Tunisian barley varieties.

Table 4. Pearson’s correlation test between the antioxidant activity (DPPH assay) and the individual phenolic compounds.

	GC-GC-C	CGl	PB3	Catechin	VA	HFG	DPPH
GC-GC-C	1
CGl	0.9002	1
PB3	0.8368	0.8309	1
Catechin	0.4285	0.0116	0.3501	1
VA	0.9431	0.9938	0.8458	0.1169	1
HFG	0.7331	0.9364	0.8530	−0.1630	0.9013	1
DPPH	−0.7894	−0.9606	−0.8754	0.0943	−0.9343	−0.9962	1

Values in bold are different from 0 with a significance level alpha = 0.05.

GC-GC-C: gallocatechin–gallocatechin–catechin; CGl: catechin-3-glucose; PB3: procyanidin B3; VA: vanillic acid; HFG: hydroferuloyl glucose; DPPH: 1,1-difenyl-2-picrylhydrazyl.

Figure 6. Scores plot obtained by principal component analysis of different barley varieties based on their antioxidant activity and individual phenolic compounds contents.