2 Carotenoids in Phototrophic Microalgae …
35
shifts at 0.88, 1.25, and 1.56 ppm are due to the terminal methyl groups of fatty acids,
olefinic methylene of fatty acids, and water, respectively. Nostoxanthin, caloxanthin,
zeaxanthin, β-cryptoxanthin, and β-carotene show corresponded identical
1 H-NMR
spectra of the β-end group, 3-hydroxy β-end group, and 2,3-dihydro β-end group
(Takaichi et al. 1990). An example of NMR data of neurosporene is presented in
Takaichi and Maoka (2015).
(vi) Chirality elucidation from circular dichroism (CD) spectra
Some carotenoids such as zeaxanthin and α-carotene have chiral carbon(s). Absolute
configurations of carotenoids are determined with CD spectra (Buchecker and Noack
1995).
Natural α-carotene and its derivatives, such as lutein and siphonaxanthin, have a
(6
R) conformation at the ε-end group. Exceptionally, α-carotene from cyanobacteria
of Acaryochloris exhibits opposite chirality, (6
S)-α-carotene. Both CD spectra are
mirror images (Takaichi et al. 2012).
(vii) “Carotenoids Handbook”
This book (Britton et al. 2004) contains more than 700 types of carotenoids with their
spectroscopic data, sources of organisms, and references, and is useful for checking
the identity of any newly isolated carotenoids.
(viii) Compare with phylogenetic systematics
In general, natural compounds and their metabolic pathways are strongly related to
phylogenetic systematics. These are very useful controls for analysis of carotenoids
and useful tools for thinking about metabolic pathways. In purple bacteria, the variation of carotenoids and carotenogenic pathways can be explained as the deletion
and/or addition of one or two enzymes (Takaichi 2009). In cyanobacteria (Fig. 2.3),
it can be explained as the presence or absence of carotenogenic enzymes and characteristics of the enzymes (Takaichi and Mochimaru 2007). Genus or family-specific
carotenoids have been reported including synechoxanthin (Graham et al. 2008) and
myxol glycoside (Takaichi and Mochimaru 2007) in cyanobacteria, and siphonaxanthin esters in the Chlorophyta (Yoshii et al. 2005). Exceptionally in prokaryote,
the horizontally transfer of a gene cluster to other bacteria has been found (Petersen
et al. 2012).
In some reports, a bacterium contained diverse carotenoids with unrelated
synthetic pathways. However, it is not likely that the bacterium contains so many
carotenogenic enzymes. Therefore, this result is likely to be due to misidentification
of carotenoids.
(ix) Carotenogenic genes from genome DNA sequences
Recently, determining genomic DNA sequences has become easier, especially among
prokaryotes. After a homologous search for carotenogenic genes, in some cases,
35
shifts at 0.88, 1.25, and 1.56 ppm are due to the terminal methyl groups of fatty acids,
olefinic methylene of fatty acids, and water, respectively. Nostoxanthin, caloxanthin,
zeaxanthin, β-cryptoxanthin, and β-carotene show corresponded identical
1 H-NMR
spectra of the β-end group, 3-hydroxy β-end group, and 2,3-dihydro β-end group
(Takaichi et al. 1990). An example of NMR data of neurosporene is presented in
Takaichi and Maoka (2015).
(vi) Chirality elucidation from circular dichroism (CD) spectra
Some carotenoids such as zeaxanthin and α-carotene have chiral carbon(s). Absolute
configurations of carotenoids are determined with CD spectra (Buchecker and Noack
1995).
Natural α-carotene and its derivatives, such as lutein and siphonaxanthin, have a
(6
R) conformation at the ε-end group. Exceptionally, α-carotene from cyanobacteria
of Acaryochloris exhibits opposite chirality, (6
S)-α-carotene. Both CD spectra are
mirror images (Takaichi et al. 2012).
(vii) “Carotenoids Handbook”
This book (Britton et al. 2004) contains more than 700 types of carotenoids with their
spectroscopic data, sources of organisms, and references, and is useful for checking
the identity of any newly isolated carotenoids.
(viii) Compare with phylogenetic systematics
In general, natural compounds and their metabolic pathways are strongly related to
phylogenetic systematics. These are very useful controls for analysis of carotenoids
and useful tools for thinking about metabolic pathways. In purple bacteria, the variation of carotenoids and carotenogenic pathways can be explained as the deletion
and/or addition of one or two enzymes (Takaichi 2009). In cyanobacteria (Fig. 2.3),
it can be explained as the presence or absence of carotenogenic enzymes and characteristics of the enzymes (Takaichi and Mochimaru 2007). Genus or family-specific
carotenoids have been reported including synechoxanthin (Graham et al. 2008) and
myxol glycoside (Takaichi and Mochimaru 2007) in cyanobacteria, and siphonaxanthin esters in the Chlorophyta (Yoshii et al. 2005). Exceptionally in prokaryote,
the horizontally transfer of a gene cluster to other bacteria has been found (Petersen
et al. 2012).
In some reports, a bacterium contained diverse carotenoids with unrelated
synthetic pathways. However, it is not likely that the bacterium contains so many
carotenogenic enzymes. Therefore, this result is likely to be due to misidentification
of carotenoids.
(ix) Carotenogenic genes from genome DNA sequences
Recently, determining genomic DNA sequences has become easier, especially among
prokaryotes. After a homologous search for carotenogenic genes, in some cases,