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Arsenolipids in brown algae Ectocarpus
Ásta H. Pétursdóttir1,2,3, Kyle Fletcher3, Helga Gunnlaugsdóttir1, Frithjof Kuepper3 and Jörg Feldmann2
Introduction
Results
•  Seaweed is growing in popularity, e.g. for
cooking, snacking, as a food supplement
and as well in various skincare products.
•  Seaweed is high in nutrients, such as
minerals and vitamins, however, can have
high total arsenic (totAs) conc.
•  The majority is on the form of
arsenosugars, with low percentage of
toxic inorganic arsenic (iAs), Figure 2.
•  Arsenolipids (AsLps) have recently been
found in seaweeds, Figure 1.
•  Arsenic accumulates in seaweed since
phosphate transporters take up arsenate
(iAs) in addition to the phosphate.
•  Biosynthetic pathway for the formation of
arsenolipids has been suggested but not
proven.
•  The totAs was determined in all fractions: lipid soluble (LS), water
soluble (WS) and residue (RS), Figure 5.
•  AsLp and AsSugar profiles quantified with ICPMS and identified with
ESIMS, Figures 7.
40
35
10
5
WS
EC-Abdn
LS
EC-CB
RS
Elachista
Pylaiella
b)
totAs
1.4
8
1.2
7
1
6
conc. mg / kg
5
4
3
2
0.8
0.6
0.4
0.2
1
S3-As
S3-AsN
S3-AsP
S3-AsOS
d)
S3-Ctrl
S3-N
S3-P
S3-OS
S3-AsOS
S3-AsP
S3-As
S3-P
S3-N
RS
S3-AsN
LS
S3-OS
WS
S3-Ctrl
S2-OS
S2-P
S2-N
S2-Ctrl
S1-OS
S1-P
S1- N
S1-Ctrl
c)
S2-Ctrl
S2-N
S2-P
S2-OS
0
0
S1-Ctrl
S1- N
S1-P
S1-OS
conc. mg / kg
Figure 2. Toxicity profile of seaweed.
Figure 5. Distribution between water soluble arsenic species (WS), lipid soluble arsenicals (LS) and
the arsenic still bound in the residue (RS) after sequential extraction for: a) Ectocarpales species
found in natural habitat, includes the total arsenic (totAs) c) Ectocarpus cultures. Also a close up of
the LS fraction: b) Ectocarpales d) cultures. Error bars represent standard deviation.
conc. mg / kg
0.2
S3 ctrl
S3 -N
*
*
0.15
S3 -P
S3 -OS
*
*
0.1
*
*
*
*
*
*
0.05
0
a)
AsHC360
30.2 min
AsPL (32.5 min) AsPL (33.8 min) AsPL (35.3 min) AsPL (39.1 min) AsPL (44.5 min)
S1, S2, S3
and S3+As
b)
S3 ctrl + As
S3 -N +As
S3 -P +As
s3 - OS+As
*
*
*
0.3
0.25
•  The concentration of AsLps is similar in EC cultures and EC nature,
Figure 5.
•  Majority of arsenic in cultures is non-extractable, Figure 5.
•  Bound in membranes?
•  AsHC360 is the main AsLp in EC cultures and EC nature.
•  Good repeatability between 3 replicate cultures, Figure 6.
•  Increased production of AsLps under stress for S1-S2 (not shown).
•  Additional arsenic in media leads to higher production of AsHCs,
Figure 6 a) and b).
•  For low phosphate conditions there is a significant increase in
production of AsPLs (S3) but no AsSugars containing phosphate
were present (S1-S3), Figure 6.
*
*
*
*
AsHC360
Figure 4. Schematic of the sample design
Biotechnology and Biomolecules
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
conc. mg / kg
•  Three strains (S1-S3) of Ectocarpus grown at:
Ctrl: Control (1/2 Provasoli)
N: Low nitrate (1/3 N of ctrl)
P: Low phosphate (1/3 P of ctrl)
OS: Oxidative stress (+ H2O2)
•  S3 also grown +2 ppb arsenic.
•  As conc. in provasoli media 0.8 ppb.
conc. mg / kg
Figure 3. Instrumental setup
Sample design
Analysis and Consulting
15
9
Materials and methods
Conclusions
20
a)
•  Grow Ectocarpus (EC) from single cell and compare to naturally
growing Ectocarpus and related algae.
§  Study the dependence of AsLps and AsSugars on environmental
conditions such as nutritional status and oxidative stress.
§  Will nutrient deficient seaweed conserve N or P, e.g. by
replacing choline in phospholipids (PL) with arsenosugar?
•  Seaweed samples extracted in
methanol/dichloromethan (1:2)
and AsLps seperated on reverse
phase (RP) C18 column and
introduced simultanously to ICPMS and ES-MS (orbitrap).
•  Extracted in water and AsSugars
measured on HPLC-ICP-MS with
anion exchange column
•  totAs in residue determined.
25
0
Ec-rvk 12-8 EC-rvk-17-8 Hincksia
Ref: Feldmann and Krupp. 2011. Anal Bioanal Chem.
Aim and hypotheses
conc. mg / kg
Figure 1. Examples of arsenolipids (AsLps)
conc. mg / kg
30
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
30.3 min
*
*
*
**
*
AsPL(31.9 min) AsPL (32.7 min) AsPL (33.6 min) AsPL (35.3 min) AsPL (39.1 min) AsPL (44.7 min)
S3-As
S3-AsN
S3-AsP
S3-AsOS
0.2
0.15
0.1
0.05
c)
0
Void
AsSugOH
Rt 3.3 (min)
AsSugPO4
AsSugSO3
Figure 7. a) Arsenolipid profiles and quantification for S3. Condition statistically significant
from ctrl using ANOVA: *P<0.05, **P<0.001 b) Arsenolipid profiles and quantification for S3
at enriched arsenic conditions. c) AsSugar profile and quantification for S3 + As.
Ásta H. Pétursdóttir ([email protected]; http://www.matis.is)
Matís ltd 2Dept of Chemistry, University of Aberdeen,
Scotland. 3Ocean lab, University of Aberdeen, Newburgh,
Scotland.
1
Food Safety, Environment and Genetics
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The Icelandic Research Fund
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