METABOLITES FROM MARINE ALGAE

1. Phycocolloids2. Mycosporine-like amino acids

Phycocolloids

Polysaccharides that are structural components of sea weeds.

From Rhodophyceae – Agar and carrageenan (sulfated polysaccharides)

From Phaeophyceae – Alginate (made of mannuronic acid and guluronic acid)

Agar synthesis

Assembly of galactopyranosyl units on the primers in Golgi Sulfation ring closure and methylation migration towards cell wall matrix

Quality and content of agar differs with physico-chemical characteristics (seasons)

G.gracilis and G.bursa –pastoris, Gelidium sps

Low quality agar- food products,adhesive,paper sizing, textile printing

Medium quality – gel substrate in biological culture media,laxatives,anticoagulants

High quality agar – separation techniques in molecular biology

Carrageenan

Water-soluble sulfated galactans The macroalga Kappaphycus alvarezii has been

grown in large scale to supply carrageenan to the food industries.

Other sources - Chondrus crispus and Gigartina stellata

Used widely as emulsifiers and stabilisers in milk-based products.

K-carrageenan is used for its thickening and suspension properties in food industry

Have antitumor and immunomodulation activities.

K-carrageenan L-carrageenan

Alginate

Used in textile industry for sizing cotton yarn

Used in food and pharma industries due to its ability to chelate metal ions and form viscous solutions.

Sources – Laminaria sps, Sargassam,Lessonia nigrescens

The intercellular alginate gel matrix gives the plant both mechanical strength and flexiblity.

Mycosporine-like Amino acids

Secondary metabolites that act as “microbial sunscreen” – absorbs UV light

Have cyclohexanone/cycloheximine chromophore with 2 or more amino acids

Biosynthesized in algae by the shikimic acid pathway.

Other marine organisms obtain them by symbiotic associations

Antioxidant properties and role in stress responses

Mycosporine-glycine quenches ROS and confers protection against the oxidative stress

MAA-rich cyanobacteria provide antioxidant activity in Oceanic ecosystems that have high O2 conc.

4-deoxygadusol,its precursor, also has such properties and is retrobiosynthesized.

Type of stress

Definition Action of MAA

Salt stress Difficulty in balancing intracellular fluids,in a Hyper/hypotonic environment.

High conc. Accumulates inside cell cytoplasm and contributes to osmotic pressure.

Desiccation

Water becomes a growth-limiting factor

Accumulates in large amounts in the ECM

Thermal stress

Temperatures inhibitory to growth

Conc. upregulated

Uses

Used in Suncare products

A product called Helioguard® 365 that contains mycosporine-like amino acids from the red alga Porphyra umbilicalis has been commercialized.

Synthetic analogues are also tested for the same purpose.

Used as photostabilising agents in paints ,plastics, and varnish