Maria Chiara Fontanellaa, R. D’Amatob, D. Businellib and G.M. Beonea

aDepartment for Sustainable Process, Università Cattolica del Sacro Cuore, Piacenza, Italy.

bDepartment of Agricultural, Environmental and Food Science, University of Perugia, Perugia, Italy

Selenium biofortification in rice

SUMMARY

² Selenium Introduction ² Selenium biofortification in rice (article) ² Antimony introduction ² Effects of Selenium on Antimony uptake in rice ² Conclusions ² Future perspectives

-  an ambivalent element: essential for human nutrition but toxic at high concentration -  Se content of most of foods is very low, the Se requirement of the body can be satisfied with dietary supplements or with Se-enriched foods -  Se agronomic biofortification crop by selenate (Se(VI) or selenite (Se(IV)) -  Se(VI) è washed out by irrigation/rainfall -  Se(IV) è adsorbed by soil minerals -  Different Se incorporation in agriculture field (aqueous solution in soils o spraying on leaves)

Selenium (Se)

q  High Se concentration in roots than in shoots

q  C-Se-C compounds being the dominant species of Se in all roots (Wang et al. 2015)

SELENITE (Se(IV))

q  Se(IV) is transformed into organic Se in roots, limit translocation in shoots

q  Selenite uptake into the plant may occur via phosphate transporters (Li et al. 2008) or passive diffusion (Shrift and Ulrich, 1969; Arvy, 1993) and/or a silicon (Si) influx transporter Lsi1 (OsNIP2;1) (Zhao et al., 2010).

Selenium in rice

Selenium Biofortification in Rice (Oryza sativa L.) Sprouting: Effectson Se Yield and Nutritional Traits with Focus on Phenolic Acid ProfileRoberto D’Amato,† Maria Chiara Fontanella,‡ Beatrice Falcinelli,† Gian Maria Beone,‡ Elisabetta Bravi,†

Ombretta Marconi,† Paolo Benincasa,*,† and Daniela Businelli†

†Department of Agricultural, Food and Environmental Sciences, University of Perugia, 06121 Perugia, Italy‡Department for Sustainable Food Process, Universita ̀ Cattolica del Sacro Cuore of Piacenza, 29100 Piacenza, Italy

*S Supporting Information

ABSTRACT: The contents of total Se and of inorganic and organic Se species, as well as the contents of proteins, chlorophylls,carotenoids, and phenolic acids, were measured in 10-day old sprouts of rice (Oryza sativa L.) obtained with increasing levels (15,45, 135, and 405 mg Se L−1) of sodium selenite and sodium selenate and with distilled water as control. Increasing Se levelsincreased organic and inorganic Se contents of sprouts, as well as the content of phenolic acids, especially in their solubleconjugated forms. Moderate levels of sodium selenite (i.e., not higher that 45 mg L−1) appeared the best compromise to obtainhigh Se and phenolic acid yields together with high proportion of organic Se while limiting residual Se in the germinationsubstrate waste. Se biofortification of rice sprouts appears a feasible and efficient way to promote Se and phenolic acid intake inhuman diet, with well-known health benefits.KEYWORDS: sprout, selenium species, phenolic acid, carotenoid, chlorophyll

■ INTRODUCTION

Selenium (Se) is an essential micronutrient for mammals,involved in major metabolic pathways like the production of awide range of selenoproteins (i.e., selenocysteine, selenome-thionine, etc.), thyroid hormone metabolism, and immunefunctions.1 The low Se status is associated with several healthdiseases (i.e., Keshan disease, heart diseases, hyperthyroidism,enhanced susceptibility to infections, cancer)1,2 and occurs ingeographic areas where the soil is particularly poor in thiselement and, consequently, the food is poor as well. The Sesupply in almost all European countries is below therecommended daily intake (50−55 μg Se).3

The procedure aimed at increasing the selenium content inplants during early stages is known as Se-biofortification andhas been developed for several plants including trees4 andvegetables.5 Within the existing compounds suitable for Se-biofortification, inorganic ones (e.g., sodium selenite andsodium selenate) are known to be cheap and efficient, whereasorganic ones (i.e., selenoproteins) are expensive although morerelevant for human nutrition. However, plants are able toproduce selenoproteins starting from inorganic Se com-pounds;1 thus, inorganic forms might be preferred becausethey are cost-effective.Se-biofortification has been recently applied for the

production of Se-enriched sprouts.6−9 Sprouts, the youngseedlings obtained a few days after seed germination, are a highvalue food produced homemade or for the ready-to-eatmarket.10 Compared to seeds, sprouts have higher nutritionaltraits such as an increased content of phytochemicals, that is,the secondary metabolites of plants, known to provide severalbenefits for human health.10 Seeds during germination are ableto absorb high amounts of Se.8,11

Rice (Oryza sativa L.) is a basic food all over the world andgluten-free,12 which makes it particularly appreciated in light ofthe increasing incidence of celiac disease. Some literature existson Se-biofortification in rice sprouts, but this was limited to lowSe concentrations (from 10 to 40 mg Se L−1) of sodiumselenite.6,11,12 No literature considered the effect of sodiumselenite at concentrations over 40 mg Se L−1 and the effect ofsodium selenate. Moreover, only Chomchan et al.12 inves-tigated the effect of Se-biofortification on sprout phenoliccontent, and they measured only the total phenolic content,with no focus on specific compounds like phenolic acids.Phenolic acids (PAs) are well represented in cereal species13

and have been found in rice sprouts, with different chemicalforms,14 implicating different bioavailability and health benefits.Soluble free (i.e., aglycones) and conjugated (i.e., ester- andglycoside-bound) PAs are easily available for absorption in thehuman large and small intestines, whereas bound ones (i.e., cellwall-bound) overcome digestion in the stomach and smallintestine. For this reason, bound PAs help reduce the risk ofcolorectal cancer and provide site-specific health benefits in thecolon and other tissues after absorption.15 Several pigments arealso reported to have health promoting effects. Among these,carotenoids,16 chlorophyll, and its derivatives.17

Since recent research demonstrated that increasing concen-trations of sodium chloride increase PAs content in cereals18 aswell as in other species,19 similarly, sodium selenite andselenate might be assumed to have an effect on PAs content ofsprouts. A wider picture on the effect of these salts might

Received: January 9, 2018Revised: March 17, 2018Accepted: April 5, 2018Published: April 5, 2018

Article

pubs.acs.org/JAFCCite This: J. Agric. Food Chem. 2018, 66, 4082−4090

© 2018 American Chemical Society 4082 DOI: 10.1021/acs.jafc.8b00127J. Agric. Food Chem. 2018, 66, 4082−4090

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1st PART: Se biofortification in rice

OBJECTIVE: Evaluate Se accumulation in sprouts as organic and inorganic forms,

and Se optimal concentrations and biofortification efficiency

Se(IV) mg L-1

water Se(IV)_15 Se(IV)_45

Se(IV)_135 Se(IV)_405

Se(VI) mg L-1

Se(VI)_15 Se(VI)_45

Se(VI)_135 Se(VI)_405

Rice (Oryza sativa L., cv. Selenio)

Se experimental design

Roots Shoots

Total Se content

Se speciation

0

20

40

roots shoots

15mgSeL-1 SeIV_15

SeVI_15

Se(IV) application causes Se accumulation mainly in roots

Se(VI) application causes Se accumulation mainly in shoots

Shoot length was not affected by Se(IV), while it was always decreased by Se(VI).

Root length increased at low level of Se(IV) and Se(VI), while it decreased at higher Se concentrations especially in Se(VI).

tSe content increased in all Se treatments (except for Se(VI)_135 and Se(VI)_405)

tSe content increased in all Se treatments.

Total selenium (tSe) content in rice roots and shoots

by higher concentrations of both. The TChlC/TCC ratio wasgenerally higher in SeIV than in SeVI and reached a maximumfor SeIV_45 (+45% compared to Se_0).Phenolic Acid Contents. Soluble free and soluble

conjugated PAs were generally increased by SeIV and SeVItreatments as compared to Se_0, while bound PAs showedirregular variations (Table 5). In most cases, soluble free PAsshowed moderate variations (except for the high increases inSeIV_135 and, especially, SeIV_405), as well as bound PAs,while soluble conjugated PAs showed dramatic increasescompared to Se_0.As far as single PAs are concerned, Se_0 showed only the

three forms of GA, plus soluble conjugated SaA, and bound α-RA, GeA, FA. Both SeIV and SeVI caused the appearance ofsoluble free SaA, soluble conjugated GeA, VA, p-CA, FA, SiA,and bound SaA, but the presence and the content of these PAsvaried with the Se level, without a clear trend. Moreover, freeFA appeared at SeIV_405 and o-CA at SeIV_135 andSeIV_405. Soluble conjugated SaA reached very highconcentrations in most SeIV and SeVI treatments, and soluble

conjugated FA reached very high concentrations in SeVItreatments.

■ DISCUSSIONResults on sprout growth parameters suggest some consid-eration about the effect of the forms and levels of selenium(Table 1). The increase of sprout mass and root length forselenite and selenate at the lowest Se level (i.e., 15 mg Se L−1)would suggest a stimulatory effect, a sort of a hormetic effect.27

The decrease of all growth parameters at higher Se levels couldbe due to a toxic effect of Se on rice sprouts.28 A reduction ofgrowth for Se (as selenite) levels of 25 mg L−1 or higher wasalso observed for chickpea sprouts by Zhang et al.29 The toxiceffect of Se would be greater in case of selenate, which caused adelay of germination and growth in SeVI_135 and the completelack of germination in SeVI_405. The slightly higher dry matter% content of sprouts in SeVI_135 was due to their earliergrowth stage so that the proportion of the grain compared toroots and shoots was still important (Table 1). The higherphytotoxicity of selenate compared to selenite was also

Table 3. Inorganic and Organic Se Species and Protein Content in Shoots of 10-Day Old Rice Sproutsa

Se species (μg g−1 DM)

inorganic species organic species

treatments SeO32− SeO4

2− total SeCys2 SeMeSeCys SeMet totalproteins

(mg BSA g−1 DM)

Se_0 0.02 (0.01) g <LOD 0.02 (0.01) h <LOD <LOD 0.06 (0.01) h 0.06 (0.01) f 110 (1.75) bSeIV_15 0.98 (0.03) f <LOD 0.98 (0.03) g 1.24 (0.20) e 2.55 (0.13) f 2.80 (0.23) g 6.58 (0.50) e 107 (1.65) bcSeIV_45 1.58 (0.16) e <LOD 1.58 (0.16) f 1.65 (0.08) d 10.1 (0.28) c 5.62 (0.42) f 17.4 (0.75) c 130 (2.82) aSeIV_135 3.62 (0.28) d 0.08 (0.01) d 3.70 (0.27) e 2.03 (0.08) c 13.2 (0.9) a 8.62 (0.44) d 23.8 (0.59) b 108 (0.49) bcSeIV_405 8.49 (0.17) a 0.06 (0.02) de 8.55 (0.18) c 2.63 (0.19) b 11.2 (0.59) b 10.3 (0.45) b 24.1 (0.05) ab 103 (2.16) cSeVI_15 1.66 (0.20) e 3.95 (0.11) c 5.61 (0.31) d 1.34 (0.09) e 1.57 (0.07) g 6.46 (0.37) e 9.37 (0.45) d 92.3 (1.37) dSeVI_45 5.64 (0.24) c 57.2 (1.34) a 62.8 (1.10) a 3.55 (0.10) a 4.86 (0.09) e 9.51 (0.24) c 17.9 (0.35) c 78.5 (1.85) eSeVI_135 7.59 (0.29) b 44.1 (1.54) b 51.7 (1.39) b 2.48 (0.12) b 7.81 (0.13) d 14.6 (0.12) a 24.9 (0.18) a 51.9 (3.32) f

aObtained with distilled water (Se_0) or at 15, 45, 135, and 405 mg L−1 of sodium selenite (SeIV_15, SeIV_45, SeIV_135, and SeIV_405) and 15,45, 135 mg L−1 of sodium selenate (SeVI_15, SeVI_45, SeVI_135). Average values for n = 3 independent replicates, each analyzed in triplicate, arereported. Standard deviations in brackets. Different letters within each column indicate statistically significant differences at p < 0.05. SeO3

2−,selenite; SeO4

2−, selenate; SeCys2, selenocystine; SeMeSeCys, Se-(methyl)selenocysteine; SeMet, selenomethionine.

Figure 1. HPLC-ICP-MS chromatogram of samples from rice sprouts fortified with sodium selenite (SeIV_45, solid line) and sodium selenate(SeVI_45, dotted line). Peak identities: A = SeCys2; B = SeMetSeCys, C = SeMet, D = SeO3

2−, E = SeO42−.

Journal of Agricultural and Food Chemistry Article

DOI: 10.1021/acs.jafc.8b00127J. Agric. Food Chem. 2018, 66, 4082−4090

4085

010203040506070

Se_0 SeIV_15 SeIV_45 SeIV_135SeIV_405 SeVI_15 SeVI_45 SeVI_135

mgkg-1

DM

treatments

Seorg iSe

Organic (orgSe) and inorganic (iSe) selenium distribution in shoots (1/2)

SELENITE TREATMENT

SELENATE TREATMENT

0%10%20%30%40%50%60%70%80%90%100%

Se_0 SeIV_15 SeIV_45 SeIV_135 SeIV_405 SeVI_15 SeVI_45 SeVI_135

treatments

%iSe%Seorg

169 7 8 9 4 3

34 5348

34

106 10

75

3730

31

32

43

1219

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Se_0 SeIV_15 SeIV_45 �SeIV_135 �SeIV_405 SeVI_15 SeVI_45 �SeVI_135

%iSe%SeMet%SeMeCys%SeCys2

Organic (orgSe) and inorganic (iSe) selenium distribution in shoots (2/2)

Se(IV) application causes Se accumulation mainly in roots

Se(VI) application causes Se accumulation mainly in shoots

Shoot length was not affected by Se(IV), while it was always decreased by Se(VI).

Root length increased at low level of SeIV and SeVI, while it decreased at higher Se concentrations especially in SeVI.

tSe content increased in all Se treatments (except for Se(VI)_135 and Se(VI)_405)

tSe content increased in all Se treatments.

Total Se content and speciation in rice roots and shoots

Higher values of OrgSe in Se(IV) treatment (SeMet and SeMeCys). Higher values of iSe in Se (VI) treatment.

2nd PART:

Effects of Selenium on Antimony uptake in rice (Oryza sativa L.): speciation analysis

OBJECTIVES: Investigate uptake and translocation of Sb in rice plants Se-biofortified or not, exposed to Sb(III) and Sb(V) at increased concentrations under hydroponic

condition.

Study how Se influences/is influenced by the different Sb concentrations in the distribution of organic (SeCys2, SeMeSeCys and SeMet) and inorganic forms

[Se(IV), Se(VI)] of selenium from roots to shoots.

-  priority pollutants

-  Sb(III) and Sb(V)

-  Sb(III) more toxic than Sb(V) species

-  Sb(V) has octahedral structure, larger radius (Å=3.68)

-  Sb(V) is the predominant species in soil solution like Sb(OH)-6.

-  Sb(V) transport requires mediation by transporters

-  Sb(III) cross cell membranes passively with water (aquaporins)

Sb

water Se(IV) 1 mg L-1 Se(IV) 10 mg L-1

water

Sb(III)1 Sb(III)27

Sb(V)1 Sb(V)27

water

Sb(III)1 Sb(III)27

Sb(V)1 Sb(V)27

water

Sb(III)1 Sb(III)27

Sb(V)1 Sb(V)27

Rice (Oryza sativa L., cv. Selenio)

Se and Sb experimental design

7 days of Se biofortification 7 days of hydroponic contact of Sb species

Roots Shoots

HPLC - ICP-MS

ICP-MS Octapole Reaction System

Total Se, Sb content

Se and Sb speciation

0.25 g DM +8 mL of ultrapure HNO3 (65%w/w)

+2 mL H2O2 (30%w/w)

Microwave digestion

Dilution with water up to 20 mL

Filtration

0.1 g FM +4 mL of water

+1,5 mL protease

stirred in water bath at 37 °C for 4 h

Centrifugation

Supernatant filtration

Ammonium acetate

(gradient analysis)

Na2EDTA + KHP (isocratic analysis)

Materials and method

RESULTS Sb and Se distribution in roots and shoots

0

20

40

60

80

100

Se1 Se10 Sb(III)1 Sb(III)1+Se1 Sb(III)1+Se10 Sb(III)27 Sb(III)27+Se1Sb(III)27+Se10

Shoots-Sb(III)treatment Sb Se

tSb and tSe distribution in roots and shoots (Sb(III)+Se in hydroponic solution)

0

50

100

150

200

250

300

Se1 Se10 Sb(III)1 Sb(III)1+Se1 Sb(III)1+Se10 Sb(III)27 Sb(III)27+Se1 Sb(III)27+Se10

roots-Sb(III)treatment Sb Se

0

5

10

15

mgkg

-1

Shoots-Sb(III)treatment

Sb

A A A

BBC

C

0

50

100

150

200

250

300

mgkg

-1

roots-Sb(III)treatment

Sb

A

B B

C

A A 0

100

200

300 Sb

+82%

0

5

10

15

Sb(III)27 Sb(III)27+Se10

Sb

+40%

SYNERGIC EFFECT

tSb distribution in roots and shoots (Sb(III)+Se in hydroponic solution)

Sb(III) 1mg L-1 Sb(III) 27mg L-1

Sb(III)1 Sb(III)1+Se1 Sb(III)1+Se10 Sb(III)27 Sb(III)27+Se1 Sb(III)27+Se10

Sb(III)1 Sb(III)1+Se1 Sb(III)1+Se10 Sb(III)27 Sb(III)27+Se1 Sb(III)27+Se10

Sb(III)27 Sb(III)27+Se10

0

50

100

150

200

Se1 Se10 Sb(III)1 Sb(III)1+Se1 Sb(III)1+Se10 Sb(III)27 Sb(III)27+Se1Sb(III)27+Se10

roots-Sb(III)treatment

Se

b b b

0

20

40

60

80

100

Se1 Se10 Sb(III)1 Sb(III)1+Se1 Sb(III)1+Se10 Sb(III)27 Sb(III)27+Se1Sb(III)27+Se10

Shoots–Sb(III)treatment

Se

b bc c

0

20

40

60

80

100

Se10 Sb(III)1+Se10

Se

-22%

tSe distribution in roots and shoots (Sb(III)+Se in hydroponic solution)

tSb and tSe distribution in roots and shoots (Sb(V)+Se in hydroponic solution)

0

50

100

150

200

Se1 Se10 Sb(V)1 Sb(V)1+Se1 Sb(V)1+Se10 Sb(V)27 Sb(V)27+Se1 Sb(V)27+Se10

roots-Sb(V)treatmentSb Se

0

20

40

60

80

100

120

140

Se1 Se10 Sb(V)1 Sb(V)1+Se1 Sb(V)1+Se10 Sb(V)27 Sb(V)27+Se1 Sb(V)27+Se10

Shoots-Sb(V)treatment Sb Se

0

20

40

60

80 roots-Sb(V)treatment

Sb

A A A

B B B

Sb(V)1 Sb(V)1+Se1 Sb(V)1+Se10 Sb(V)27 Sb(V)27+Se1 Sb(V)27+Se10

0

5

10

15Shoots-Sb(V)treatment

Sb

A A A

CBC B

Sb(V)1Sb(V)1+Se1Sb(V)1+Se10 Sb(V)27Sb(V)27+Se1Sb(V)27+Se10

0

5

10

15

Sb(V)27 Sb(V)27+Se10

Sb

-17%

Antagonistic effect

tSb distribution in roots and shoots (Sb(V)+Se in hydroponic solution)

Sb(V) 1mg L-1 Sb(V) 27mg L-1

0

50

100

150

200

Se1 Se10 Sb(V)1 Sb(V)1+Se1 Sb(V)1+Se10 Sb(V)27 Sb(V)27+Se1 Sb(V)27+Se10

roots-Sb(V)treatment

Se

0

50

100

150

Se1 Se10 Sb(V)1 Sb(V)1+Se1 Sb(V)1+Se10 Sb(V)27 Sb(V)27+Se1Sb(V)27+Se10

Shoots-Sb(V)treatment

Se

b

b

ba

bb

0

20

40

60

80

100

120

140

Se10 Sb(V)1+Se10Sb(V)27+Se10

Se+19%

+34%

tSe distribution in roots and shoots (Sb(V)+Se in hydroponic solution)

tSb content is higher in roots than shoots under Sb(III) and Sb(V) treatments.

Sb(III) is accumulated more easily than Sb(V) 0

2

4

6

8

mgkg

-1

SbatlowSbdosage

Sb(III)1Sb(V)1

SHOOTSROOTS

tSb decreased with high level of Se (Sb(V)27+Se10) (antagonistic effect)

tSe is higher in roots than shoots under Sb(III) and Sb(V) treatments.

tSe increased with low and high Sb(V) levels

tSe decreased at low level of Sb(III)

Sb(III) and Sb(V) treatments don’t influence tSe content

tSb increased with high level of Se (Sb(III)27+Se10) (synergic effect).

tSb increased with high level of Se (Sb(III)27+Se10) (synergic effect).

RESULTS Organic (orgSe) and inorganic (iSe) selenium

distribution

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Se(IV)1 Sb(III)1+Se(IV)1 Sb(III)27+Se(IV)1 Se(IV)10 Sb(III)1+Se(IV)10 Sb(III)27+Se(IV)10

SHOOTS-Sb(III)treatment %iSe %orgSe

a bc

A

0

20

40

60

80

100

Se10 Sb(III)1+Se10

Se

-22%

c a b

B

d

BC C D D

Se 1

Organic (orgSe) and inorganic (iSe) selenium distribution

45e62f

35d27c

19b9a

9(b)

1(a)

1(a) 16(c)

64(e)

29(d)

28B 1A

29B4A

3A

34B

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Se(IV)1 Sb(III)1+Se(IV)1 Sb(III)27+Se(IV)1 Se(IV)10 Sb(III)1+Se(IV)10 Sb(III)27+Se(IV)10

SHOOTS–Sb(III)treatment

%iSe %Met %MeSeCis %Cys

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Se(IV)1 Sb(V)1+Se(IV)1 Sb(V)27+Se(IV)1 Se(IV)10 Sb(V)1+Se(IV)10 Sb(V)27+Se(IV)10

SHOOTS-Sb(V)treatment %iSe %orgSe

AAB B BBD

0

20

40

60

80

100

120

140

Se10 Sb(V)1+Se10Sb(V)27+Se10

Se+19%

+34%

b b a bbc c

45c34b 29b 27b

54c

12a

9(b)

1(a)1(a)

16(c)

5(b)

49(d)

28B

29B26B 4A

1A 0A

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Se(IV)1 Sb(V)1+Se(IV)1 Sb(V)27+Se(IV)1 Se(IV)10 Sb(V)1+Se(IV)10 Sb(V)27+Se(IV)10

SHOOTS-Sb(V) %iSe %Met %MeSeCis %Cys

Ø  Sb and Se are more stored in roots than in shoots

Ø  Synergic effect of Se on Sb(III) in roots and shoots

Ø  Antagonistic effect of Se on Sb(V) in shoots

Ø  Sb treatments exhibit consequences on Se contents in shoots

(negative with Sb(III) and positive with Sb(V))

CONCLUSIONS

Future perspectives

Improving knowledge about plant behaviour of other rice varieties

Deepening Sb influences on rice seedling in soil plots, until grains production.

Instrumental upgrade (different nebulizer for sensitivity improves, UHPLC-triple quad-ICP MS)

Thank You!