ACTA BIOLOGICA CRACOVIENSIA

16 TH INTERNATIONAL SYMPOSIUM ON CAROTENOIDS
Synthesis of stabilized carotenoids as
molecular wires
Hyungjun Kim1 , Juwan Maeng1 , Soo Bong Kim1 ,
Nam Joo Lee 1 , Eunho Choi1 , Se-Young Jung1 , Inseok Hong1 ,
Boram Lim 1 , Chi Jung Kang1,2 , Sangho Koo1,3 1 Department of Nano Science and Engineering, 2 Department of
Physics, 3 Department of Chemistry, Myong Ji University, Yongin,
Kyunggi-Do, 449-728, Korea, sangkoo@mju.ac.kr
Carotenoids are adopted by Nature as electron shuttles in various
biological processes and are the most potent organic molecular
wires (Frank et al., 2004). The inherent instability of carotenoids
in vitro, however, does not allow full investigation of the potentials
of these biological molecular wires. We devised the conceptually
new and seemingly stable artificial carotenoids containing
the phenyl groups with a para-substituent X (OMe, Me, H, and
Br) of diverse electronic natures at C-13 and C-13’ positions,
which provided the carotenoids with various conductance as well
as stability (Meang et al., 2010). The stability of carotenoids by
the phenyl groups might be expected from the repulsive steric
interactions with attacking nucleophiles and/or the reversible
trapping of incoming radicals (e.g. reactive oxygen species) that
would cause fragmentations of the conjugate polyene chain of
carotenoids.
An electric circuit has been assembled by embedding
carotenoids in an insulating and supporting monolayer of
methyl(octadecyl)sulfane on a gold surface. Adsorptions of
methyl(octadecyl)sulfane and carotenoids on a gold substrate
were confirmed by XPS. The self-assembly of 2 nm-size gold particles
on top of the other methylthio group of the embedded
carotene wires completed the electric circuit. A gold-coated AFM
probe was used as an electrode to contact the carotenoid molecule
through a gold nanoparticle. Reproducible measurement of
molecular conductance has been reported by through-bond contacts
between molecules and gold particles (Cui et al., 2001).
The orthogonal phenyl substituents (p-X-C 6 H 4 -) to the polyene
chain increase the conductance according to the electrondonating
capability of X. The carotenoid containing two electronreleasing
para-anisyl groups (X = OMe) gives the highest conductance
of 33.46 nS. An electron-withdrawing para-bromophenyl
group (X = Br) provides more resistance rather than
conductance. The most resistive carotenoid among the series is
the wire containing two para-bromophenyl groups, and its conductance
value is 3.37 nS. It is believed that electron transport of
a molecular wire proceeds through the frontier orbital of the molecule,
which is closest to the Fermi levels of the electrode, and
that the electronic effect of the substituents may shift the frontier
molecular orbital and alter the electron transport efficiency
through the molecule. The electron-donating substituent (X)
places the LUMO of the carotenoid closer to the Fermi level of
gold electrode than the electron-withdrawing substituent does,
and thereby facilitates the electron transport process.
REFERENCES
FRANK HA and BRUDVIG GW. 2004. Redox functions of carotenoids in
photosynthesis. Biochemistry 43: 8607-8615.
MEANG J, KIM SB, LEE NJ. CHOI E, JUNG SY, HONG I, BAE SH, OH JT, LIM
B, KIM JW, KANG CJ, KOO S. 2010. Conductance control in stabilized
carotenoids wires. Chemistry A European Journal
16:7395-7399.
CUI XD, PRIMAK A, ZARATE X, TOMFOHR J, SANKEY OF, MOORE AL, MOORE
TA, GUST D, HARRIS G, LINDSAY SM. 2001. Reproducible measurement
of single-molecule conductivity. Science 294:571-574.
A HPLC method for the simultaneous
determination of geometrical isomers of major
carotenoids in human plasma
Antonio J. Meléndez-Martínez1,2 , Chun Liu2 ,
Xiang-Dong Wang 2
1 Food Colour & Quality Lab., Dept. Nutrition & Food Science.
Universidad de Sevilla, Facultad de Farmacia, C/P. García
González 2, 41012 Sevilla, Spain
2 Nutrition and Cancer Biology Laboratory, Jean Mayer Human
Nutrition Research Center on Aging at Tufts University, 711
Washington Street, MA 02111 Boston, United States, ajmelendez@us.es,
chun.liu@tufts.edu, xiang-dong.wang@tufts.edu
The development of the HPLC C30 stationary phase can facilitate
the study of the occurrence of geometrical isomers of carotenoids
in human blood from different sources. The study of geometrical
isomers is interesting as they are known to have a different
metabolism and function in terms of susceptibility to oxidation,
bioavailability, vitamin A activity, etc. In the present study we
developed a new HPLC method for the simultaneous determination
of the geometrical isomers of major carotenoids found in
human plasma and tissues. For this purpose, appropriate standards
including lutein, zeaxanthin, β-cryptoxanthin, α-carotene,
β-carotene, lycopene, phytoene and phytofluene were dissolved in
ethanol and stereomutated by heating at temperatures around
80°C for some 30 minutes. The combination of aliquots of such
extracts was used for the optimization of the separation of the isomers
on a YMC C30 column (3 μm, 4.6 × 150 mm) by using
methanol and methyl-tert-butyl ether in the mobile phase. Up to
46 peaks were separated in 61 minutes by this method. The
analysis of the posprandial plasma carotenoid responses of a
human volunteer of Asian ethnicity 24 hours after the consumption
of a vegetable mix (carrot, celery, beets, parlsey, lettuce,
watercress, spinach) and tangerine juices revealed the presence
of (all-E)-β-carotene, (all-E)-β-cryptoxanthin, (all-E)-lutein, (all-E)lycopene
and several (Z)-isomers of the two latter carotenoids.
The analysis of that fraction in a human volunteer of Caucasian
ethnicity 4 hours after the intake of thermally-processed carrots
and orange peppers, and juices containing mixed vegetables and
fruits (mango, peach and orange) revealed the presence of (all-E)α-carotene,
(all-E)-β-carotene, (all-E)-β-cryptoxanthin, (all-E)zeaxanthin,
(all-E)-lutein, (all-E)-lycopene and several (Z)-isomers
of the three latter carotenoids. No detectable levels of either phytoene
or phytofluene were found, although the method proved
suitable for their determination. However we detected, in addition
to β-carotene and lycopene isomers, two geometrical isomers of
phytoene and 5 of phytofluene in lung tissue of ferrets receiving a
diet containing tomato extract supplement. To the best of our
knowledge, this is the report of the highest number of carotenoid
geometrical isomers separated with a HPLC method.
Controlling aggregation – carotenoids
aggregates with predefined size
Eugenia Mariana Sandru 1 , Arnljot Elgsaeter 2 ,
Hans-Richard Sliwka 1 , Vassilia Partali 1
SESSION 3
1 Department of Chemistry, 2 Department of Physics , Norwegian
University of Science and Technology, Realfagbygget, 7491
Trondheim, Norway, eugenia-mariana.sandru@nt.ntnu.no
Nearly all carotenoids are hydrophobic. Their inherent hydrophobicity
limits carotenoid application in water-based environment.
Carotenoids research is therefore often restricted to organic solvents.
Recently, carotenoids were modified with hydrophilic
groups making them water-soluble and water-dispersible [1,2].
52 ACTA BIOLOGICA CRACOVIENSIA Series Botanica