Anti-Oxidant, Anti-Diabetic, and Anti-Hypertensive Effects of Extracted Phenolics and Hydrolyzed Peptides from Barley Protein Fractions

Figures & data

Table 1 Content of total free and bound phenolic compounds extracted from barley flour, partial homogeneous protein fractions, and protein isolate expressed as (mg/g DW)

Protein fraction	Total phenolics ^1 for FP-23°C extract	Total phenolics ^1 for FP-60°C extract	Total phenolics ^1 for BP-base extract	Total phenolics ^1 for BP-acid extract
Globulin-fraction	0.14^d	0.21^d	0.29^d	0.81^d
Glutein-1-fraction	0.15^c	0.23^c	0.32^c	0.47^f
Glutein-2-fraction	0.14^d	0.18^e	0.21^e	0.72^e
Prolamin fraction	0.20^a	0.44^a	0.35^b	1.36^a
Protein isolate	0.16^bc	0.17 ^e	0.72^a	1.00^b
Barley flour	0.17^b	0.35^b	0.69^a	0.91^c
^1Expressed in terms of gallic acid equivalent.
Mean values (n = 2) with the same superscript in a column are not significantly different (p > 0.05). DW: Dry weight.

Table 2 Antioxidant activities (%) of free and bound phenolic compounds extracted from barley flour, partial homogeneous protein fractions, and protein isolate

Protein fraction	Antioxidant activity of FP-23°C extract	Antioxidant activity of FP-60°C extract	Antioxidant activity of BP-base extract	Antioxidant activity of BP-acid extract
Globulin-fraction	45.62^d	46.95^d	47.37^c	47.49^e
Glutein-1-fraction	41.85^e	47.24^d	27.51^e	59.08^c
Glutein-2-fraction	44.59^d	51.42^c	40.28^d	56.74^d
Prolamin fraction	55.61^a	60.19^b	66.80^b	65.38^b
Protein isolate	49.90^c	69.98^a	70.23^a	72.84^a
Barley flour	52.72^b	63.08^b	68.40^b	60.43^c
Mean values (n = 3) with the same superscript in a column are not significantly different (p > 0.05).

Table 3 ACE inhibitory activity (%) of free and bound phenolic compounds extracted from barley flour, partial homogeneous protein fractions, and protein isolate

Protein fraction	ACE inhibitory activity for FP-23°C extract	ACE inhibitory activity for FP-60°C extract	ACE inhibitory activity for BF-base extract	ACE inhibitory activity for BP-acid extract
Globulin-fraction	52.0b^c	56.3^e	59.0^d	57.0^d
Glutein-1-fraction	41.0^c	63.0^d	63.3^d	72.7^c
Glutein-2-fraction	71.7^ab	74.7^b	71.7^c	58.7^d
Prolamin fraction	79.3^a	82.0^a	87.0^a	80.7^a
Protein isolate	65.0^ab	60.3^d	72.3^c	78.0^ab
Barley flour	71.0^ab	68.7^c	79.7^b	76.3^b
Mean values (n = 3) with the same superscript in a column are not significantly different (p > 0.05). Expressed in terms of percentage of inhibition.

Table 4 α-Amylase inhibitory activity (%) of free and bound phenolic compounds extracted from barley flour, partial homogeneous protein extracts, and protein isolate

Protein fraction	α-Amylase inhibitory activity of FP-23°C extract	α-Amylase inhibitory activity of FP-60°C extract	α-Amylase inhibitory activity of BP-base extract	α-Amylase inhibitory activity of BP-acid extract
Globulin-fraction	45.0^c	46.7^c	49.7^c	51.3^cd
Glutein-1-fraction	36.0^e	39.3^e	32.3^e	43.7^e
Glutein-2-fraction	41.0^d	43.0^d	45.7^d	49.3^d
Prolamin fraction	66.0^a	68.0^a	72.0^a	76.7^a
Protein isolate	51.0^b	54.3^b	57.0^b	57.3^b
Barley flour	44.0^c	46.7^c	49.7^c	52.7^c
Mean values (n = 3) with the same superscript in a column are not significantly different (p > 0.05).

Table 5 ACE inhibitory activity (%) and antioxidant activity (%) of barley peptides hydrolyzed with combined pepsin and trypsin enzymes at 6 h extracted from barley flour, partial homogeneous protein fractions, and protein isolate

Protein fraction	ACE inhibitory activity of peptide extract (%)	Antioxidant activity of peptide extract (%)
Globulin-fraction	48.3^b	54.3^b
Glutein-1-fraction	33.0^d	38.3^e
Glutein-2-fraction	44.3^bc	47.0^d
Prolamin fraction	61.3^a	77.7^a
Protein isolate	40.7^c	51.3^c
Barley flour	32.3^d	47.0^d
Mean values (n = 3) with the same superscript in a column are not significantly different (p > 0.05).

Figure 1 Effect of incubation time of pepsin enzyme on degree of hydrolysis (DH) for barley flour and protein fractions: ◊ Globulin-1-fraction, □ Glutein-fraction, ♦ Glutein-fraction, Prolamin-fraction, Protein isolate, Barley flour. (Color figure available online.)

Figure 2 Effect of incubation time for trypsin enzyme on degree of hydrolysis (DH) for barley flour and protein fractions: ◊ Globulin-1-fraction, □ Glutein-fraction, ♦ Glutein-fraction, Prolamin-fraction, Protein isolate, Barley flour. (Color figure available online.)

Figure 3 Effect of incubation time for combined pepsin and trypsin enzymes on degree of hydrolysis (DH) for barley flour and protein fractions: ◊ Globulin-1-Fraction, □ Glutein-Fraction, ♦ Glutein-Fraction, Prolamin-Fraction, Protein isolate, Barley flour. (Color figure available online.)

Table 6 Correlation coefficients (r) between content, α-amylase inhibitory activity, antioxidant activity, and ACE inhibitory activity of phenolic compounds of barley proteins

			α-Amylase inhibitory
	Antioxidant activity	ACE inhibitory activity	activity
Total content	0.524	0.367	0.509
Antioxidant activity		0.584	0.647
ACE inhibitory activity			0.627

Table 7 Correlation coefficients (r) between degree of hydrolysis, antioxidant activity and ACE inhibitory activity of barley peptides hydrolyzed with combined pepsin and trypsin enzymes at 6 h

ACE inhibitory	Antioxidant activity	activity
Degree of hydrolysis	0.940	0.850
ACE inhibitory activity		0.919