J Food Bioact

Journal of Food Bioactives, ISSN 2637-8752 print, 2637-8779 online

Journal website www.isnff-jfb.com

Original Research

Volume 6, June 2019, pages 118-130

Fertilizer micro-dosing and harvesting time of indigenous leafy vegetables affect in vitro antioxidant activities

Figure 1. Chromatograms of polyphenolics compounds from Amaranthus cruentus (a), Ocimum gratissimum (b) and Solanum macrocarpon (c) produced with D60 and collected at first harvesting time.

Figure 2. Chromatograms of polyphenolics compounds from Ocimum gratissimum produced with D0 (a), D20 (b), D40 (c), D60 (d) and D80 (e) and collected at first harvesting time.

Figure 3. DPPH (a, b, c), hydroxyl (d, e, f) and superoxide (g, h, i) radical scavenging activities of polyphenol extracts from Amaranthus cruentus (a, d, g), Ocimum gratissimum (b, e, h) and Solanum macrocarpon (c, f, i).

Figure 4. Ferric ion reducing power (a, b, c) of, ferrous ions chelation (d, e, f) and inhibition of linoleic acid oxidation (g, h, i) by polyphenol extracts from Amaranthus cruentus (a, d, g), Ocimum gratissimum (b, e, h) and Solanum macrocarpon (c, f, i).

Figure 5. Inhibition of linoleic acid oxidation by polyphenol extracts from Amaranthus cruentus (a), Ocimum gratissimum (b) and Solanum macrocarpon (c) in comparison to blank.

**Table 1.** Effect of fertilizer dose (FD) and harvest time (HT) on polyphenols contents and antioxidant activities of vegetables species
Variables	Amaranthus cruentus	Ocimum gratissimum	Solanum macrocarpon
Units: ¹mg/g; ²EC₅₀, mg/mL; ³%; ⁴mM Fe²⁺/mg. Abbreviations: DPPH-RSA: DPPH radical scavenging activity; HRSA: hydroxyl radical scavenging activity; SRSA: superoxide radical scavenging activity; FRAP: ferric ions reducing antioxidant power; FIC: ferrous ions chelation; ILAO: inhibition of linoleic acid oxidation. ^aF-value. ^bData from highest concentration tested (5 μg/mL for A. cruentus and S. macrocarpon and 1.5 mg/mL for O. gratissimum). ^cData used were those from the first two harvests of D0, D20, D40 and D60. ^dDdata from lowest concentration tested (0.25 mg/mL) at highest inhibition day (day 4). ^eData used were those from D0, D20, D40 and D60. Significance: p < 0.05, p < 0.01, **p < 0.001.
Polyphenolic compounds	Caffeic acid¹	883^a*	430^*	2014^*	16	416^*	56	41	173^*	141
Catechin¹	81	85	12	162^*	56	217^*	55	297^*	49
Gallic acid¹	1172^*	2144^*	115	912^*	1019^*	2802^*	154	1052^*	129
Myricetin¹	138	40498^**	1096^*	41	210^*	64	19	3	31
Quercetin¹	782^*	456^*	514^*	2	561^*	49	19	9	42
Rutin¹	2402^*	2279^*	524^*	2377^*	1351^*	345^*	1639^*	458^*	82
Antioxidant activities	DPPH-RSA²	9^*	80^**	20^*	778^***	2051^***	113^***	18^**	6340^***	90^**
HRSA^3b	6^c	110^**c	6^c	247^***	5519^***	2240^***	159^***	1078^**	94^**
SRSA^3b	93^**	58^**	85^**	191^**	389^**	54^**	40^**	201^***	80^**
FRAP⁴	1583^***	1401^**	533^***	659^***	210659^***	4331^***	379^**	14578^***	1559^***
FIC²	3503^***	81280^***	547^***	1906^***	15228^***	330^***	7	502^***	10^*
ILAO^3d	5651^***e	45228^***e	5126^***e	468^***	2389^***	576^***	4021^***	4055^***	4308^***

Table 1. Effect of fertilizer dose (FD) and harvest time (HT) on polyphenols contents and antioxidant activities of vegetables species

Variables

Amaranthus cruentus

Ocimum gratissimum

Solanum macrocarpon

FDxHT

Units: ¹mg/g; ²EC₅₀, mg/mL; ³%; ⁴mM Fe²⁺/mg. Abbreviations: DPPH-RSA: DPPH radical scavenging activity; HRSA: hydroxyl radical scavenging activity; SRSA: superoxide radical scavenging activity; FRAP: ferric ions reducing antioxidant power; FIC: ferrous ions chelation; ILAO: inhibition of linoleic acid oxidation. ^aF-value. ^bData from highest concentration tested (5 μg/mL for A. cruentus and S. macrocarpon and 1.5 mg/mL for O. gratissimum). ^cData used were those from the first two harvests of D0, D20, D40 and D60. ^dDdata from lowest concentration tested (0.25 mg/mL) at highest inhibition day (day 4). ^eData used were those from D0, D20, D40 and D60. Significance: *p < 0.05, **p < 0.01, ***p < 0.001.

Polyphenolic compounds

Caffeic acid¹

883^a*

430^*

2014^*

416^*

173^*

141

Catechin¹

162^*

217^*

297^*

Gallic acid¹

1172^*

2144^*

115

912^*

1019^*

2802^*

154

1052^*

129

Myricetin¹

138

40498^**

1096^*

210^*

Quercetin¹

782^*

456^*

514^*

561^*

Rutin¹

2402^*

2279^*

524^*

2377^*

1351^*

345^*

1639^*

458^*

Antioxidant activities

DPPH-RSA²

9^*

80^**

20^*

778^***

2051^***

113^***

18^**

6340^***

90^**

HRSA^3b

6^c

110^**c

6^c

247^***

5519^***

2240^***

159^***

1078^**

94^**

SRSA^3b

93^**

58^**

85^**

191^**

389^**

54^**

40^**

201^***

80^**

FRAP⁴

1583^***

1401^**

533^***

659^***

210659^***

4331^***

379^**

14578^***

1559^***

FIC²

3503^***

81280^***

547^***

1906^***

15228^***

330^***

502^***

10^*

ILAO^3d

5651^***e

45228^***e

5126^***e

468^***

2389^***

576^***

4021^***

4055^***

4308^***

**Table 2.** Correlation between polyphenol compounds and antioxidant activities of leafy vegetable species
Variables	TPC¹	TFC²	Caffeic acid³	Catechin³	Gallic acid³	Myricetin³	Quercetin³	Rutin³	DPPH-RSA⁴	HRSA⁵	SRSA⁵	FRAP⁶	FIC⁴	ILAO⁵
Units: ¹GAE mg/g; ²RE mg/g; ³mg/g; ⁴EC₅₀, mg/mL;⁵%; ⁶mM Fe²⁺/mg. Abbreviations: TPC: total phenolics content; TFC: total flavonoids content; DPPH-RSA: DPPH radical scavenging activity; HRSA: hydroxyl radical scavenging activity; SRSA: superoxide radical scavenging activity; FRAP: ferric ions reducing antioxidant power; FIC: ferrous ions chelation; ILAO: inhibition of linoleic acid oxidation. Significance: p < 0.05, *p < 0.01.
TPC¹	1.000
TFC²	−0.397^**	1.000
Caffeic acid³	−0.100	0.083	1.000
Catechin³	0.353^*	−0.410^**	−0.192	1.000
Gallic acid³	0.104	−0.134	0.054	0.107	1.000
Myricetin³	−0.373^*	0.491^**	−0.170	−0.207	−0.127	1.000
Quercetin³	0.331^*	−0.353^*	−0.054	0.148	0.081	−0.263	1.000
Rutin³	0.220	0.093	−0.123	0.194	0.041	0.264	−0.100	1.000
DPPH-RSA⁴	0.770^**	−0.531^**	0.105	0.238	0.070	−0.330^*	0.233	0.043	1.000
HRSA⁵	−0.355^*	0.040	0.100	−0.101	0.250	−0.356^*	−0.022	−0.345^*	−0.368^*	1.000
SRSA⁵	−0.184	0.159	0.578^**	−0.026	0.235	−0.422^**	−0.042	−0.282	−0.174	0.639^**	1.000
FRAP⁶	−0.466^**	0.129	0.046	−0.184	0.098	−0.149	−0.158	−0.275	−0.509^**	0.878^**	0.435^**	1.000
FIC⁴	−0.303^*	0.533^**	0.632^**	−0.291	−0.306^*	0.169	−0.149	0.055	−0.346^*	0.029	0.471^**	0.085	1.000
ILAO⁵	−0.461^**	0.172	0.086	−0.113	0.006	0.157	0.224	−0.065	−0.297^*	0.150	0.135	0.082	0.190	1.000

Table 2. Correlation between polyphenol compounds and antioxidant activities of leafy vegetable species

Variables

TPC¹

TFC²

Caffeic acid³

Catechin³

Gallic acid³

Myricetin³

Quercetin³

Rutin³

DPPH-RSA⁴

HRSA⁵

SRSA⁵

FRAP⁶

FIC⁴

ILAO⁵

Units: ¹GAE mg/g; ²RE mg/g; ³mg/g; ⁴EC₅₀, mg/mL;⁵%; ⁶mM Fe²⁺/mg. Abbreviations: TPC: total phenolics content; TFC: total flavonoids content; DPPH-RSA: DPPH radical scavenging activity; HRSA: hydroxyl radical scavenging activity; SRSA: superoxide radical scavenging activity; FRAP: ferric ions reducing antioxidant power; FIC: ferrous ions chelation; ILAO: inhibition of linoleic acid oxidation. Significance: *p < 0.05, **p < 0.01.

TPC¹

1.000

TFC²

−0.397^**

1.000

Caffeic acid³

−0.100

0.083

1.000

Catechin³

0.353^*

−0.410^**

−0.192

1.000

Gallic acid³

0.104

−0.134

0.054

0.107

1.000

Myricetin³

−0.373^*

0.491^**

−0.170

−0.207

−0.127

1.000

Quercetin³

0.331^*

−0.353^*

−0.054

0.148

0.081

−0.263

1.000

Rutin³

0.220

0.093

−0.123

0.194

0.041

0.264

−0.100

1.000

DPPH-RSA⁴

0.770^**

−0.531^**

0.105

0.238

0.070

−0.330^*

0.233

0.043

1.000

HRSA⁵

−0.355^*

0.040

0.100

−0.101

0.250

−0.356^*

−0.022

−0.345^*

−0.368^*

1.000

SRSA⁵

−0.184

0.159

0.578^**

−0.026

0.235

−0.422^**

−0.042

−0.282

−0.174

0.639^**

1.000

FRAP⁶

−0.466^**

0.129

0.046

−0.184

0.098

−0.149

−0.158

−0.275

−0.509^**

0.878^**

0.435^**

1.000

FIC⁴

−0.303^*

0.533^**

0.632^**

−0.291

−0.306^*

0.169

−0.149

0.055

−0.346^*

0.029

0.471^**

0.085

1.000

ILAO⁵

−0.461^**

0.172

0.086

−0.113

0.006

0.157

0.224

−0.065

−0.297^*

0.150

0.135

0.082

0.190

1.000