366
M. C. Deprá et al.
Grignard reaction, two moles of ß-C19-aldehyde are condensed with acetylene to
form ß-C40-diol. By elimination of two molecules of water with simultaneous allylic
rearrangement, the ß-C40-diol is transformed into ß-carotene. Partial hydrogenation
in catalyst presence gives 15, 15’ -cis-ß-carotene, which is isomerized in elevated
boiling petroleum ether to crystalline all-trans-ß-carotene (Isler et al. 1967; Pfander
et al. 1997; Ernst 2002).
In 1960, a higher yield method (85%) was developed by BASF. This method was
underpinned on the Wittig condensation and follows C 20 + C 20 synthesis principle,
at where phosphonium salt, preliminarily derivatized with triphenylphosphine, react
with an aldehyde, resulting in a double bond and increasing the polyenic chain. In
Fig. 15.2, the reaction occurs between retinal and retinyltriphenylphosphonium salt
(Ribeiro et al. 2011). The Wittig reaction is today the most important reaction for the
synthesis of carotenoids, as it allows the formation of carbon–carbon double bonds
in a specific location in the molecule. However, this reaction has a disadvantage, such
as the environmentally undesirable formation of triphenylphosphine oxide (Britton
et al. 1996; Ribeiro et al. 2011; Gong and Bassi 2016).
Without exception, the C40-carotenoids produced by Hoffman-La Roche and
BASF synthetic pathways have symmetrical structures, once that they have identical
end-groups (Ernst 2002).
The astaxanthin is a xanthophyll carotenoid subclass, characterized by the presence of oxygen molecule in their structure, that is similar to β-carotene and other
xanthophylls, such as lutein, canthaxanthin, and zeaxanthin, in that they share a
common semi-symmetric layout with two terminal carbon rings flanking a polyene
chain. However, astaxanthin is distinctive in its structure from other carotenoids due
to the presence of hydroxyl and keto moieties on both ends (Yang et al. 2013).
Many strategies have been developed to the astaxanthin synthetic synthesis from
the symmetrical C40-carotenoids, being Wittig reaction of two C15-phosphonium
salts with a C10-dialdehyde the most commonly used method (Fig. 15.3a) (Widmer
et al. 1981). Other methods include the hydroxylation of canthaxanthin (Fig. 15.3b)
(Bernhard et al. 1984), a C10 + C20 + C10 synthesis via dienolether condensation
(Rüttimann 1999), and the isomerization of lutein to zeaxanthin and then oxidation
to astaxanthin (Fig. 15.3c) (Schloemer and Davis 2002).
Given the technological aspect, the process of synthetic production of these
pigments involves more compact and optimized equipment which reflects in a
processing plant with less occupation of the physical space and with lower spending
on electricity (Fig. 15.4) (Isler 1971; Pommer 1977).
15.3 Microalgae-Based Pigments
The synthetic pigments proved extremely successful, their availability and reasonable
price led to more extensive use, and to attempts to find new applications and open
up new markets (Hu 2019). However, a popular view sustains that natural pigments
are innately superior to synthetic form with respect to their effects on human health,
M. C. Deprá et al.
Grignard reaction, two moles of ß-C19-aldehyde are condensed with acetylene to
form ß-C40-diol. By elimination of two molecules of water with simultaneous allylic
rearrangement, the ß-C40-diol is transformed into ß-carotene. Partial hydrogenation
in catalyst presence gives 15, 15’ -cis-ß-carotene, which is isomerized in elevated
boiling petroleum ether to crystalline all-trans-ß-carotene (Isler et al. 1967; Pfander
et al. 1997; Ernst 2002).
In 1960, a higher yield method (85%) was developed by BASF. This method was
underpinned on the Wittig condensation and follows C 20 + C 20 synthesis principle,
at where phosphonium salt, preliminarily derivatized with triphenylphosphine, react
with an aldehyde, resulting in a double bond and increasing the polyenic chain. In
Fig. 15.2, the reaction occurs between retinal and retinyltriphenylphosphonium salt
(Ribeiro et al. 2011). The Wittig reaction is today the most important reaction for the
synthesis of carotenoids, as it allows the formation of carbon–carbon double bonds
in a specific location in the molecule. However, this reaction has a disadvantage, such
as the environmentally undesirable formation of triphenylphosphine oxide (Britton
et al. 1996; Ribeiro et al. 2011; Gong and Bassi 2016).
Without exception, the C40-carotenoids produced by Hoffman-La Roche and
BASF synthetic pathways have symmetrical structures, once that they have identical
end-groups (Ernst 2002).
The astaxanthin is a xanthophyll carotenoid subclass, characterized by the presence of oxygen molecule in their structure, that is similar to β-carotene and other
xanthophylls, such as lutein, canthaxanthin, and zeaxanthin, in that they share a
common semi-symmetric layout with two terminal carbon rings flanking a polyene
chain. However, astaxanthin is distinctive in its structure from other carotenoids due
to the presence of hydroxyl and keto moieties on both ends (Yang et al. 2013).
Many strategies have been developed to the astaxanthin synthetic synthesis from
the symmetrical C40-carotenoids, being Wittig reaction of two C15-phosphonium
salts with a C10-dialdehyde the most commonly used method (Fig. 15.3a) (Widmer
et al. 1981). Other methods include the hydroxylation of canthaxanthin (Fig. 15.3b)
(Bernhard et al. 1984), a C10 + C20 + C10 synthesis via dienolether condensation
(Rüttimann 1999), and the isomerization of lutein to zeaxanthin and then oxidation
to astaxanthin (Fig. 15.3c) (Schloemer and Davis 2002).
Given the technological aspect, the process of synthetic production of these
pigments involves more compact and optimized equipment which reflects in a
processing plant with less occupation of the physical space and with lower spending
on electricity (Fig. 15.4) (Isler 1971; Pommer 1977).
15.3 Microalgae-Based Pigments
The synthetic pigments proved extremely successful, their availability and reasonable
price led to more extensive use, and to attempts to find new applications and open
up new markets (Hu 2019). However, a popular view sustains that natural pigments
are innately superior to synthetic form with respect to their effects on human health,