Ioannis Zabetakis
Associate Professor in Food Chemistry, Dept. Biological Sciences, UL

Bioactive Lipids of Marine Microalga Chlorococcum sp. SABC 012504 with Anti-Inflammatory and Anti-thrombotic Activities

/ Blog

This is a post about our latest paper on marine microalgae

 

The value of Marine Microalgae

Marine microalgae are the pioneering photosynthetic organisms with significant morphological, genetic, and biochemical diversity. They are playing an important role in the biosphere, supplying nutrition to both aquatic and terrestrial food chains. Microalgae are ubiquitously distributed throughout the biosphere and exposed to high-oxygen and free-radical stresses, which has led to the evolution of efficient anti-oxidative defence mechanisms [1]. Marine algae living in the competitive harsh environments have developed specialised defence strategies by biosynthesising chemically and structurally diverse compounds through different metabolic pathways [2]. Microalgae are the “treasure house”, as rich sources of proteins, essential fatty acids, carbohydrates, pigments, vitamins, minerals, and several other bioactive molecules, with anti-oxidant, anti-inflammatory, antithrombotic, anti-bacterial, anti-diabetic, anti-fungal, anti-viral, anti-parasitic, anti-proliferative, anti-elastase, anti-trypsin, anti-chymotrypsin, angiotensin I-converting enzyme inhibitory (ACE-inhibitory), myofibroblast differentiation inducing, hepatic fibrosis inhibitory, etc. [3,4,5,6,7].

 

 

Microalgae and Inflammation

Inflammation and thrombosis are implicated in several chronic disorders, such as cardiovascular diseases, cancer, and persistent infections, such as the new coronavirus disease 2019 (COVID-19) pandemic [8,9,10,11]. Platelet-activating factor (PAF) and thrombin are key mediators of the inflammatory and thrombo-inflammatory manifestations implicated in the onset and/or development of such disorders [9]. These mediators activate several pathways and cells of the immune system, including platelets, through specific receptors in the membranes of these cells. The abnormal activation of human platelets is implicated in thrombosis and/or pathological bleeding although these cells are critically involved in normal haemostasis [9,12,13]. Recent research has emphasised on the beneficial effects of marine polar lipids (PL) towards inflammation related disorders, through an array of beneficial bioactivities. These beneficial effects were reported due to their anti-inflammatory and antithrombotic activities through mechanisms, such as the inhibition of the PAF and thrombin related pathways, and the modulation of PAF metabolism towards reducing PAF-levels [8,9,14,15].
Nowadays, microalgae are considered one of the most promising feedstocks for sustainable source of various commodities for food, feed, cosmetics, and other applications [5,6]. Several microalgae have already been commercially produced for their use as nutrient-rich food, feed, and health promoting bioactive compounds [7]. However, many more microalgae are yet to be commercialised with their already known bioactivities, and on-going research activities may further identify microalgae as new potential sources for bioactive compounds. Chlorococcum is one such microalga that has not been thoroughly researched for commercial exploitation, except there are few academic studies related to carotenoid and lipids analysis. Chlorococcum is unicellular green microalgae of Chlorophyceae, found both in freshwater and marine habitats. The cells of microalga are spherical or slightly oblong with varied cell sizes, which may live as solitary or in irregular clump of cells. This green microalga has a single cup-shaped, parietal chloroplast with a single pyrenoid [7]. Chlorococcum was known to produce carotenoids: astaxanthin, adonixanthin, canthaxanthin, β-carotene, lutein, and ketocarotenoids [16,17]. Generally, during carotenogenesis process microalgae accumulates lipids with specific fatty acids production that esterifies with carotenoids and, thus, helps the organism survive the stress conditions [18]. In a study for biodiesel production, it was found that a freshwater Chlorococcum sp. RAP13 was well adapted to marine growth condition and can accumulate up to 38% lipids (of dry weight biomass) under heterotrophic condition [19].

Our research hypothesis

The marine Chlorococcum sp. lipids have not been tested yet towards the inflammatory and thrombotic pathways of PAF and thrombin. Therefore, in this manuscript, we have characterised the lipid fractions of marine microalga Chlorococcum sp. for anti-PAF and antithrombin activities with a view that the microalga can be an alternative sustainable source for the above bioactivities.

 

 

Conclusions

The in vitro assays of the present study showed that the glycolipid and phospholipid fractions of marine microalga Chlorococcum sp. SABC 012504 possess strong anti-PAF and antithrombin activities in human platelets. These bioactivities are likely due to the presence of specific novel Chlorococcum sp. SABC 012504 SQDG molecules, HexCer-t36:2 (t18:1/18:1 and 18:2/18:0) cerebrosides with a phytosphingosine base, phosphatidylcholine (PC), and phosphatidylethanolamine (PE) molecules in their lipid fractions. These bioactive PC and PE molecules with n-3 PUFA ALA or the MUFA OA were earlier reported from other natural sources, including marine, to possess strong antagonistic and agonistic effects against the PAF pathway of human platelet aggregation. Therefore, as evidenced in this study, the microalga Chlorococcum sp. has potential as a dietary supplement for these bioactivities.

 

 

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