ALGAL PIGMENTS DIFFERENT PIGMENTS FOUND IN ALGAE AND THEIR ROLE IN ECOSYSTEM

Algae have been identified as natural producer of bioactive commercial pigments. To perform photosynthesis, algae use pigments to harvest sunlight energy. The pigments found in algae are categorized in chlorophylls, phycobilins, and carotenoids. Popular carotenoids include astaxanthin, lutein, fucoxanthin, canthaxanthin, zeaxanthin, β-cryptoxanthin and finds application as antioxidant, anti-inflammatory, immunoprophylactic, antitumor activities.
Classification

1. ALGAL PIGMENTS
DIFFERENT PIGMENTS FOUND IN ALGAE AND THEIR ROLE IN ECOSYSTEM
Algae have been identified as natural producer of bioactive commercial pigments. To perform
photosynthesis, algae use pigments to harvest sunlight energy. The pigments found in algae are
categorized in chlorophylls, phycobilins, and carotenoids. Popular carotenoids include
astaxanthin, lutein, fucoxanthin, canthaxanthin, zeaxanthin, β-cryptoxanthin and finds
application as antioxidant, anti-inflammatory, immunoprophylactic, antitumor activities.



Classification of Algal pigments :The pigment is one of the most important criteria used in
differentiation of classes in algae. The pigments in algae can be chlorophylls, carotenoids and
biloproteins. These pigments are present in sac like structures called thylakoids. The thylakoids
are arranged in stacks in the granum of the chloroplasts. Different groups of algae have different
types of pigments and organization of thylakoids in chloroplast. The chlorophylls in algae are
chlorophyll a, b, c, d and e types. Chlorophyll a is present in all classes of algae.
Chlorophyll is found in all photosynthetic organisms, including green plants, cyanobacteria, and
algae Chlorophyll is composed of a porphyrin-ring system that is very similar to that of

2. hemoglobin but has a magnesium atom instead of an iron atom. The algae have four types of
chlorophyll, a, b, c and d. Chlorophyll a is the primary photosynthetic pigment in all
photosynthetic algae. Chl a has two main absorption bands in vitro, one band in the red light
region at 663 nm and the other in violet region at 430 nm
Chlorophylls are green pigments found in cyanobacteria and the chloroplasts of different algae.
Chlorophylls absorb light most strongly in the blue portion of the electromagnetic spectrum
followed by the red portion. There are different types of Chlorophyll pigments.Their structures
are based on a chlorin ring at the center of which is a magnesium ion. The structure can have
different side chains depending on the type of Chlorophyll.
Cholrophyll a: Chlorophyll a is the most widely occurring and universal type of Chlorophyll.
Molecular formula of Chlorophyll a is C55H72O5N4Mg. Chlorophylls are green pigments with
a porphyrin ring. Molecular structure consists of a chlorin ring with Mg center. The chlorin ring
is a heterocyclic compound derived from pyrrole. Four nitrogen atoms from the chlorin surround
and bind the magnesium atom. This is a stable ring-shaped molecule around which electrons are
free to migrate. It also has side chains and a hydrocarbon trail. It contains only methyl groups
(CH3) as side chains with a long hydrophobic tail, which anchors the molecule to other
hydrophobic proteins in the thylakoid membrane of the chloroplast. It absorbs light from red,
blue and violet wavelengths and gets its colour by reflecting green. It is used in oxygenic
photosynthesis. This photosynthetic pigment is essential for photosynthesis in eukaryotes,
cyanobacteria and prochlorophytes because of its role as primary electron donor in the electron
transport chain.
Chlorophyll a also transfers resonance energy in the antenna complex, ending in the reaction
center where specific chlorophylls P680 and P700 are present. Within the reaction centers of
both photosystems, there are a pair of chlorophyll a molecules that pass electrons on to the
transport chain through redox reactions Chlorophyll b: Chlorophyll b occurs only in green algae.
It absorbs most effectively at blue 470 but also at 430 and 640. Molecular formula is
C55H70O6N4Mg. It is an accessory photosynthetic pigment. Molecular structure consists of a
chlorin ring with Mg center. It also has side chains and a hydrocarbon (phytol) tail. Pyrrole ring
II contains an aldehyde group (- CHO). It absorbs energy that chlorophyll a does not absorb. It
functions as a Light harvesting Antenna in Photosystem I.

3. Xanthophylls: They are yellow pigments that form one of the two major groups of the
carotenoids. They are generally a C40 terpenoid compounds formed by condensation of isoprene
units. They contain oxygen atoms. They contain their oxygen either as hydroxyl groups and/or
as pairs of hydrogen atoms that are substituted by oxygen atoms acting as a bridge. Xanthophyll
acts as an accessory light harvesting pigment. They have critical structural and functional role in
the photo synthesis of plants and algae. They also serve to absorb and dissipate excess light
energy or work as antioxidants. They may be involved in inhibiting lipid peroxidation.
Fucoxanthin: It is a carotenoid which performs a limited role in the photosynthesis in Brown
Algae (Phaeophyta). It is responsible for the brown or olive-green colour of these algae.
Molecular formula is C42H58O6. Fucoxanthin absorbs red light to perform photosynthesis. It is
produced abundantly by Laminalia japonica, Undaria pinnatifida, Sargassum fulvellum etc. It is
a kind of xanthophyll being an oxygenated carotene. Brown algae have most species living in
the ocean. They employ fucoxanthin for photosynthesis. The pigment is sensitive to shorter
wavelengths of light. It is the main carotenoid produced in the brown algae as a component of
the light harvesting complex.
Phycocyanin: It is a pigment-protein complex from the light- harvesting phycobiliprotein
family along with the allophycocyanin and phycoerythrin. It is an accessory pigment to
chlorophyll. Being water-soluble, these pigments cannot exist within the membrane like
carotenoids. Phycocyanin has a characteristic light blue color, absorbing orange and red light
near 620 nm depending on its type and emits fluorescence at about 650 nm.

4. Phycocyanins are found in Cyanobacteria. Phycocyanin is related to the human pigment
bilirubin which is important to healthy liver function and digestion of amino acids.
Phycoerythrin: It is a red protein-pigment complex from the light-harvesting phycobiliprotein
family present in red algae and cryptophytes. It is accessory to the main chlorophyll pigments
responsible for photosynthesis. It is composed of a protein part covalently binding chromophores
called phycobilins.
In the phycoerythrin family, the most known phycobilins are phycoerythrobilins which are
typical Phycoerythrin. Other is phycourobilin. Phycoerythrins are composed of (αβ) monomers
usually organized in a disk-shaped trimer (αβ)3 or hexamer (αβ)6. In red algae, they are anchored
to the stromal side of the thylakoid membranes of chloroplasts whereas in Cryptophytes,
phycobilisomes are reduced and are densely packed inside the lumen of thylakoids
Phycoerythrin is an accessory pigment to the main chlorophyll pigments responsible for
photosynthesis. The light energy is captured by it and then passed on to the reaction centre
chlorophyll pair usually via the phycobiliproteins phycocyanin and via allophycocyanin. R-
Phycoerythrin and B- Phycoerythrin are among the brightest fluorescent dyes.
Algae contain a variety of pigments that play crucial roles in photosynthesis by capturing light
energy. The main pigments found in algae include:

5. Chlorophylls:
o Chlorophyll a: The primary pigment in all algae, crucial for capturing light
energy for photosynthesis.
o Chlorophyll b: Found in green algae (Chlorophyta), helps in capturing light and
transferring energy to chlorophyll a.
o Chlorophyll c: Found in brown algae (Phaeophyta), diatoms, and
dinoflagellates, it functions similarly to chlorophyll b.
o Chlorophyll d: Found in some red algae (Rhodophyta), it is involved in
capturing light in deeper waters where red light is less available.
o Chlorophyll e: Rare and found in some yellow-green algae (Xanthophyta).
Carotenoids:
Carotenoids are yellow, orange, or red pigments that usually occur inside the
plastid but may occur outside in certain cases. carotenoids can be divided into two
classes: (1) oxygen-free hydrocarbons, the carotenes; and (2) their oxygenated
derivatives,the xanthophylls. The most widespread carotene in the algae is β-
carotene
o Carotenes: Orange pigments that capture light for photosynthesis and provide
photoprotection.
o Xanthophylls: Yellow pigments, such as fucoxanthin in brown algae, that also
assist in light capture and provide photoprotection.

6. Fucoxanthin is the principal xanthophyll in the golden- brown algae and found in
(Chrysophyceae, Bacillariophyceae, Prymnesiophyceae, and Phaeophyceae), giving
these algae their characteristic brown color.
Phycobiliproteins:
There are 3 types of phycoerythrin: 1. R-phycoerythrin - Rhodophyta 2. B-phycoerythrin -
Rhodophyta 3. C-phycoerythrin - Cyanophyta There are also 3 types of phycocyanin: 1. R-
phycocyanin - Rhodophyta 2. C-phycocyanin - Cyanophyta 3. Allophycocyanin - Cyanophyta
o Phycocyanin: A blue pigment found in cyanobacteria (blue-green algae) and
some red algae, involved in capturing light energy.
o Phycoerythrin: A red pigment found in red algae, aiding in light capture,
particularly in deeper waters.
o Allophycocyanin: Works with phycocyanin and phycoerythrin in the light-
harvesting complexes of cyanobacteria and red algae.
Peridinin:
 Found in: Dinoflagellates.
 Function: Aids in light capture in these organisms.
 Color: Golden-brown.
Neoxanthin:
 Found in: Green algae.
 Function: Involved in light harvesting and protection from excess light.
 Color: Yellow.
Recent advancements in algal pigments :
Increasing research and development activities focused on discovering novel applications
of algal pigments, such as in nutraceuticals and biofuels, propel market growth and foster
innovation.
References:
 https://link.springer.com/article/10.1007/s43630-023-00407-3

7.  https://media.springernature.com/lw685/springer-
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 https://ars.els-cdn.com/content/image/1-s2.0-S0960852422002395-ga1_lrg.jpg
 https://easybiologyclass.com/pigments-in-algae-key-points-with-ppt/