J Food Bioact

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

Journal website www.isnff-jfb.com

Original Research

Volume 11, September 2020, pages 95-109

Amber, red and blue LEDs modulate phenolic contents and antioxidant activities in eight Cruciferous microgreens

Figure 2. Schematic of the chamber design for microgreens production. Each growth chamber was divided by a light impervious wooden barrier coated with highly reflective material, providing 1.93 m² of growing space. The lighting system in each chamber half consisted of custom-made Ceres CL LED fixtures with two 30V/200W open frame power supplies on each side, a dimmer and each growth area consisting of various ratios of red (660 nm), blue (455 nm) and amber (590 nm) LEDs.

Figure 3. Total phenolics content (TPC) (a–c) total flavonoids content (TFC) (d–f), and total anthocyanins content (TAC) (g–i) in the microgreens. Values are expressed as mean ± SD (n = 6). Values with the same letter in each group are not significantly different (p < 0.05). TPC: total phenolics content (mg gallic acid equivalent GE/g dry weight (DW)); TFC: total flavonoids content (mg catechin equivalent CE/g DW); TAC: total anthocyanin content (mg cyanidin-3-glucoside C3GE/g DW).

Figure 4. Antioxidant activities in the microgreens as measured by DPPH, FRAP and ORAC methods. Values are expressed as mean ± SD (n = 6). Values with the same letter in each group are not significantly different (p < 0.05). DPPH: 2,2-diphenyl-1-picrylhydrazyl assay (µmol Trolox equivalent Trolox equivalents TE/g dry weight (DW)); FRAP: ferric reducing antioxidant power assay (µmol ascorbic acid equivalent AE/g DW); ORAC: oxygen radical absorbance capacity assay (µmol TE/g DW).

Figure 5. Biplot of the principle components 1, 2 and 3 describe groups of phytochemicals (TPC, TFC, TAC) and antioxidant activities (DPPH, FRAP, ORAC) of eight microgreens under eight treatments. Treatments are labeled with only amber light % for legibility. Ratios are 4.73A:20.52B:74.36R; 6.74A:22.68B:70.25R; 9.51A:24.13B:65.91R; 12.02A:26.26B:61.14R; 12.57A:44.31B:42.39R; 14.53A:30.18B:51.82R; 18.45A:33.51B:47.48R; 39.46A:58.94B:0.57R. Each data point on the biplot represents averaged values of six biological repeats (n = 6). MB: Mustard, Barbarossa; MG: Mustard, Garnet giant; MO: Mizuna, organic; MR: Mizuna, red kingdom; MS: Mustard, Scarlet Frills; PC: Pac choi, red Pac; RO: Radish, red Rambo organic; RR: Radish, red Rambo

**Table 1.** Durations for germination in growth chambers for each microgreen
Microgreen	seed germination (d)	duration in growth chambers (d)	duration from seed to harvest (d)
Mizuna organic	2	13	15
Mizuna, red kingdom	2	13	15
Pac choi, red Pac	3	13	16
Mustard, Barbarossa	2	14	16
Mustard, Scarlet Frills	2	14	16
Mustard, Garnet Giant	2	14	16
Radish, red Rambo	2	13	15
Radish, red Rambo organic	2	13	15

Table 1. Durations for germination in growth chambers for each microgreen

Microgreen

seed germination (d)

duration in growth chambers (d)

duration from seed to harvest (d)

Mizuna organic

Mizuna, red kingdom

Pac choi, red Pac

Mustard, Barbarossa

Mustard, Scarlet Frills

Mustard, Garnet Giant

Radish, red Rambo

Radish, red Rambo organic

**Table 2.** Overall amber and blue light effectiveness on phenolic contents and antioxidant activities based on Pearson correlation analysis (r-Pearson)^a
Phytochemical group	TPC^b	TFC^c	TAC^d
^aValues are mean ± SD, n = 6 (six biological samples); ^bTPC: total phenolic content (mg gallic acid equivalent GAE/g dry weight (DW)); ^cTFC: total flavonoid content (mg catechin equivalent CE/g DW); ^dTAC: total anthocyanin content (mg cyanidin-3-glucoside C3GE/g DW); ^eDPPH: 2,2-diphenyl-1-picrylhydrazyl assay (µmol Trolox equivalent TE/g DW); ^fFRAP: ferric reducing antioxidant power assay (µmol ascorbic acid equivalent/g DW); ^gORAC: oxygen radical absorbance capacity assay (µmol TE/g DW).
Mizuna organic	0.50	0.68	0.40	0.49	−0.37	−0.12
Mizuna, red kingdom	0.48	0.66	0.37	0.57	−0.23	−0.18
Pac choi, red Pac	−0.30	−0.32	−0.62	−0.63	0.02	−0.33
Mustard, Barbarossa	−0.20	−0.06	0.31	0.44	−0.60	−0.68
Mustard, Garnet giant	0.28	0.53	−0.01	0.12	−0.81	−0.75
Mustard, Scarlet Frills	0.50	0.61	0.24	−0.16	−0.59	−0.64
Radish, red Rambo	0.58	0.73	0.03	0.26	−0.42	−0.25
Radish, red Rambo organic	−0.06	0.13	−0.45	−0.19	−0.78	−0.49
	DPPH^e	FRAP^f	ORAC^g
Mizuna organic	0.71	0.60	−0.01	0.34	−0.37	−0.04
Mizuna, red kingdom	0.20	0.15	0.14	0.30	−0.58	−0.48
Pac choi, red Pac	−0.01	0.00	−0.67	−0.72	0.14	0.02
Mustard, Barbarossa	−0.33	−0.38	−0.82	−0.79	−0.57	−0.67
Mustard, Garnet giant	0.52	0.62	0.67	0.48	0.55	0.64
Mustard, Scarlet Frills	0.53	0.69	0.36	0.48	−0.48	−0.26
Radish, red Rambo	0.50	0.39	0.42	0.62	−0.04	0.33
Radish, red Rambo organic	0.57	0.50	−0.10	0.10	0.59	0.83

Table 2. Overall amber and blue light effectiveness on phenolic contents and antioxidant activities based on Pearson correlation analysis (r-Pearson)^a

Phytochemical group

TPC^b

TFC^c

TAC^d

Microgreen

amber

blue

amber

blue

amber

blue

^aValues are mean ± SD, n = 6 (six biological samples); ^bTPC: total phenolic content (mg gallic acid equivalent GAE/g dry weight (DW)); ^cTFC: total flavonoid content (mg catechin equivalent CE/g DW); ^dTAC: total anthocyanin content (mg cyanidin-3-glucoside C3GE/g DW); ^eDPPH: 2,2-diphenyl-1-picrylhydrazyl assay (µmol Trolox equivalent TE/g DW); ^fFRAP: ferric reducing antioxidant power assay (µmol ascorbic acid equivalent/g DW); ^gORAC: oxygen radical absorbance capacity assay (µmol TE/g DW).

Mizuna organic

0.50

0.68

0.40

0.49

−0.37

−0.12

Mizuna, red kingdom

0.48

0.66

0.37

0.57

−0.23

−0.18

Pac choi, red Pac

−0.30

−0.32

−0.62

−0.63

0.02

−0.33

Mustard, Barbarossa

−0.20

−0.06

0.31

0.44

−0.60

−0.68

Mustard, Garnet giant

0.28

0.53

−0.01

0.12

−0.81

−0.75

Mustard, Scarlet Frills

0.50

0.61

0.24

−0.16

−0.59

−0.64

Radish, red Rambo

0.58

0.73

0.03

0.26

−0.42

−0.25

Radish, red Rambo organic

−0.06

0.13

−0.45

−0.19

−0.78

−0.49

DPPH^e

FRAP^f

ORAC^g

Mizuna organic

0.71

0.60

−0.01

0.34

−0.37

−0.04

Mizuna, red kingdom

0.20

0.15

0.14

0.30

−0.58

−0.48

Pac choi, red Pac

−0.01

0.00

−0.67

−0.72

0.14

0.02

Mustard, Barbarossa

−0.33

−0.38

−0.82

−0.79

−0.57

−0.67

Mustard, Garnet giant

0.52

0.62

0.67

0.48

0.55

0.64

Mustard, Scarlet Frills

0.53

0.69

0.36

0.48

−0.48

−0.26

Radish, red Rambo

0.50

0.39

0.42

0.62

−0.04

0.33

Radish, red Rambo organic

0.57

0.50

−0.10

0.10

0.59

0.83

**Table 3.** Net changes (%) of total phenolic, flavonoid and anthocyanin contents and antioxidant activities
	Light ratios (%, amber:blue:red)	Mustard Barbarossa	Mustard Garnet Giant	Mizuna Organic	Mustard red kingdom	Mustard Scarlet Frills	Pac choi, red Pac	Radish, red Rambo organic	Radish, red Rambo
^aTPC: mg gallic acid equivalent GAE/g dry weight; ^bTFC: mg catechin equivalent/g dry weight; ^cTAC: mg cyanidin-3-glucoside/g dry weight; ^dDPPH: µmol Trolox equivalent TE/g dry weight (DW); ^eFRAP: µmol ascorbic acid equivalent/g DW; ^fORAC: oxygen radical absorbance capacity. Values are mean ± SD (n = 6). Cells with , * and *** are significantly different from control at 5%, 1% and 0.01% and are italicized for clarity; ^nsnot significant from control (p < 0.05).
TPC^a	6.74A:22.68B:70.25R	32***	−13***	−5^ns	0^ns	−8***	−4^ns	−5^ns	−6**
9.51A:24.13B:65.91R	34***	−14***	−2^ns	4^ns	−9***	−7**	−7**	−1^ns
12.02A:26.26B:61.14R	5^ns	−1^ns	2^ns	7^ns	0^ns	3^ns	−1^ns	2^ns
12.57A:44.31B:42.39R	31***	7***	5^ns	18***	1^ns	−6**	2^ns	5**
14.53A:30.18B:51.82R	8**	−15***	−6^ns	16***	−11***	−2^ns	1^ns	3^ns
18.45A:33.51B:47.48R	34***	−13***	−1^ns	−6^ns	−3^ns	−13***	−17***	−2^ns
39.46A:58.94B:0.57R	7*	3^ns	6^ns	18***	4*	−6*	−1^ns	5**
TFC^b	6.74A:22.68B:70.25R	−1^ns	−4^ns	−4^ns	−11***	−2^ns	0^ns	−4^ns	1^ns
9.51A:24.13B:65.91R	−4^ns	−9*	−9**	3^ns	2^ns	−5^ns	−6*	1^ns
12.02A:26.26B:61.14R	0^ns	6^ns	1^ns	2^ns	2^ns	7**	4^ns	5^ns
12.57A:44.31B:42.39R	2^ns	0^ns	−1^ns	12***	−21***	−2^ns	6**	6**
14.53A:30.18B:51.82R	−4^ns	−12**	−6^ns	7*	−6**	−2^ns	−5^ns	4^ns
18.45A:33.51B:47.48R	−12***	−9*	−4^ns	4^ns	−5^ns	−3^ns	0^ns	−5^ns
39.46A:58.94B:0.57R	6^ns	−1^ns	2^ns	6^ns	5*	−8***	−9***	3^ns
TAC^c	6.74A:22.68B:70.25R	4^ns	−5^ns	−1^ns	−7^ns	0^ns	−1^ns	0^ns	1^ns
9.51A:24.13B:65.91R	5^ns	−4^ns	1^ns	−2*	0^ns	0^ns	0^ns	2^ns
12.02A:26.26B:61.14R	0^ns	−5^ns	2^ns	−1^ns	1^ns	1^ns	1^ns	1^ns
12.57A:44.31B:42.39R	−1^ns	−5^ns	2^ns	−1^ns	−1^ns	−2^ns	2^ns	1^ns
14.53A:30.18B:51.82R	1^ns	−4^ns	0^ns	0^ns	−2^ns	1^ns	0^ns	1^ns
18.45A:33.51B:47.48R	0^ns	−4^ns	0^ns	−2^ns	−1^ns	0^ns	0^ns	−1^ns
39.46A:58.94B:0.57R	−2^ns	−9^ns	−1^ns	−4^ns	−2^ns	0^ns	−3^ns	0^ns
DPPH^d	6.74A:22.68B:70.25R	3^ns	−23***	−14**	−34***	−3^ns	3^ns	0^ns	−2^ns
9.51A:24.13B:65.91R	−11**	−21***	0^ns	−29***	−18***	0^ns	−5^ns	2^ns
12.02A:26.26B:61.14R	−10*	−1^ns	−2^ns	−21***	−3^ns	4^ns	10**	−3^ns
12.57A:44.31B:42.39R	−9*	9^ns	0^ns	−23***	11**	8^ns	8*	4^ns
14.53A:30.18B:51.82R	−13***	−18***	−18***	−30***	−20***	−10^ns	−3^ns	1^ns
18.45A:33.51B:47.48R	29***	13**	41***	−8^ns	6^ns	36***	38***	46***
39.46A:58.94B:0.57R	−23***	10*	37***	−13*	16***	−4^ns	21***	18***
FRAP^e	6.74A:22.68B:70.25R	1^ns	−34***	−1^ns	−26***	18**	−3^ns	0^ns	−1***
9.51A:24.13B:65.91R	7^ns	−27***	2^ns	−20***	8^ns	6^ns	−2^ns	−7^ns
12.02A:26.26B:61.14R	3^ns	−24***	3^ns	−19***	14*	1^ns	1^ns	−11**
12.57A:44.31B:42.39R	−2^ns	−38***	12***	−9***	19**	−2^ns	2^ns	2^ns
14.53A:30.18B:51.82R	−2^ns	−18**	−8*	−19***	7^ns	−2^ns	−2^ns	−10**
18.45A:33.51B:47.48R	−8^ns	−26***	−2^ns	−26***	18**	1^ns	−9***	−8^ns
39.46A:58.94B:0.57R	−11**	21***	2^ns	−8***	16*	−9**	0^ns	2**
ORAC^f	6.74A:22.68B:70.25R	0^ns	−31^ns	27***	−9*	−2^ns	−5^ns	−19***	−11*
9.51A:24.13B:65.91R	10*	−26^ns	18***	−17***	−17***	−5^ns	−29***	−3^ns
12.02A:26.26B:61.14R	2^ns	−6^ns	5^ns	19***	−7*	−1^ns	−16***	−7*
12.57A:44.31B:42.39R	−12**	−1^ns	34***	13***	−1^ns	−10*	−10***	−5^ns
14.53A:30.18B:51.82R	−4^ns	−9^ns	13***	49***	0^ns	−3^ns	−16***	−10^ns
18.45A:33.51B:47.48R	−19***	−20^ns	1^ns	−7^ns	−16***	−17***	−9***	−10^ns
39.46A:58.94B:0.57R	−13**	11^ns	1^ns	−56***	−14***	1^ns	−17***	−14**

Table 3. Net changes (%) of total phenolic, flavonoid and anthocyanin contents and antioxidant activities

Light ratios (%, amber:blue:red)

Mustard Barbarossa

Mustard Garnet Giant

Mizuna Organic

Mustard red kingdom

Mustard Scarlet Frills

Pac choi, red Pac

Radish, red Rambo organic

Radish, red Rambo

^aTPC: mg gallic acid equivalent GAE/g dry weight; ^bTFC: mg catechin equivalent/g dry weight; ^cTAC: mg cyanidin-3-glucoside/g dry weight; ^dDPPH: µmol Trolox equivalent TE/g dry weight (DW); ^eFRAP: µmol ascorbic acid equivalent/g DW; ^fORAC: oxygen radical absorbance capacity. Values are mean ± SD (n = 6). Cells with *, ** and *** are significantly different from control at 5%, 1% and 0.01% and are italicized for clarity; ^nsnot significant from control (p < 0.05).

TPC^a

6.74A:22.68B:70.25R

32***

−13***

−5^ns

0^ns

−8***

−4^ns

−5^ns

−6**

9.51A:24.13B:65.91R

34***

−14***

−2^ns

4^ns

−9***

−7**

−1^ns

12.02A:26.26B:61.14R

5^ns

−1^ns

2^ns

7^ns

0^ns

3^ns

−1^ns

2^ns

12.57A:44.31B:42.39R

31***

7***

5^ns

18***

1^ns

−6**

2^ns

5**

14.53A:30.18B:51.82R

8**

−15***

−6^ns

16***

−11***

−2^ns

1^ns

3^ns

18.45A:33.51B:47.48R

34***

−13***

−1^ns

−6^ns

−3^ns

−13***

−17***

−2^ns

39.46A:58.94B:0.57R

3^ns

6^ns

18***

−6*

−1^ns

5**

TFC^b

6.74A:22.68B:70.25R

−1^ns

−4^ns

−11***

−2^ns

0^ns

−4^ns

1^ns

9.51A:24.13B:65.91R

−4^ns

−9*

−9**

3^ns

2^ns

−5^ns

−6*

1^ns

12.02A:26.26B:61.14R

0^ns

6^ns

1^ns

2^ns

7**

4^ns

5^ns

12.57A:44.31B:42.39R

2^ns

0^ns

−1^ns

12***

−21***

−2^ns

6**

14.53A:30.18B:51.82R

−4^ns

−12**

−6^ns

−6**

−2^ns

−5^ns

4^ns

18.45A:33.51B:47.48R

−12***

−9*

−4^ns

4^ns

−5^ns

−3^ns

0^ns

−5^ns

39.46A:58.94B:0.57R

6^ns

−1^ns

2^ns

6^ns

−8***

−9***

3^ns

TAC^c

6.74A:22.68B:70.25R

4^ns

−5^ns

−1^ns

−7^ns

0^ns

−1^ns

0^ns

1^ns

9.51A:24.13B:65.91R

5^ns

−4^ns

1^ns

−2*

0^ns

2^ns

12.02A:26.26B:61.14R

0^ns

−5^ns

2^ns

−1^ns

1^ns

12.57A:44.31B:42.39R

−1^ns

−5^ns

2^ns

−1^ns

−2^ns

2^ns

1^ns

14.53A:30.18B:51.82R

1^ns

−4^ns

0^ns

−2^ns

1^ns

0^ns

1^ns

18.45A:33.51B:47.48R

0^ns

−4^ns

0^ns

−2^ns

−1^ns

0^ns

−1^ns

39.46A:58.94B:0.57R

−2^ns

−9^ns

−1^ns

−4^ns

−2^ns

0^ns

−3^ns

0^ns

DPPH^d

6.74A:22.68B:70.25R

3^ns

−23***

−14**

−34***

−3^ns

3^ns

0^ns

−2^ns

9.51A:24.13B:65.91R

−11**

−21***

0^ns

−29***

−18***

0^ns

−5^ns

2^ns

12.02A:26.26B:61.14R

−10*

−1^ns

−2^ns

−21***

−3^ns

4^ns

10**

−3^ns

12.57A:44.31B:42.39R

−9*

9^ns

0^ns

−23***

11**

8^ns

4^ns

14.53A:30.18B:51.82R

−13***

−18***

−30***

−20***

−10^ns

−3^ns

1^ns

18.45A:33.51B:47.48R

29***

13**

41***

−8^ns

6^ns

36***

38***

46***

39.46A:58.94B:0.57R

−23***

10*

37***

−13*

16***

−4^ns

21***

18***

FRAP^e

6.74A:22.68B:70.25R

1^ns

−34***

−1^ns

−26***

18**

−3^ns

0^ns

−1***

9.51A:24.13B:65.91R

7^ns

−27***

2^ns

−20***

8^ns

6^ns

−2^ns

−7^ns

12.02A:26.26B:61.14R

3^ns

−24***

3^ns

−19***

14*

1^ns

−11**

12.57A:44.31B:42.39R

−2^ns

−38***

12***

−9***

19**

−2^ns

2^ns

14.53A:30.18B:51.82R

−2^ns

−18**

−8*

−19***

7^ns

−2^ns

−10**

18.45A:33.51B:47.48R

−8^ns

−26***

−2^ns

−26***

18**

1^ns

−9***

−8^ns

39.46A:58.94B:0.57R

−11**

21***

2^ns

−8***

16*

−9**

0^ns

2**

ORAC^f

6.74A:22.68B:70.25R

0^ns

−31^ns

27***

−9*

−2^ns

−5^ns

−19***

−11*

9.51A:24.13B:65.91R

10*

−26^ns

18***

−17***

−5^ns

−29***

−3^ns

12.02A:26.26B:61.14R

2^ns

−6^ns

5^ns

19***

−7*

−1^ns

−16***

−7*

12.57A:44.31B:42.39R

−12**

−1^ns

34***

13***

−1^ns

−10*

−10***

−5^ns

14.53A:30.18B:51.82R

−4^ns

−9^ns

13***

49***

0^ns

−3^ns

−16***

−10^ns

18.45A:33.51B:47.48R

−19***

−20^ns

1^ns

−7^ns

−16***

−17***

−9***

−10^ns

39.46A:58.94B:0.57R

−13**

11^ns

1^ns

−56***

−14***

1^ns

−17***

−14**