Antioxidant properties and lipid composition of selected microalgae
Arjun H. Banskota
1
&
Sandra Sperker
1
&
Roumiana Stefanova
1
&
Patrick J. McGinn
1
&
Stephen J. B. O’Leary
1
Received: 3 January 2018 /Revised and accepted: 16 May 2018
#
Crown 2018
Abstract
Marine and freshwater microalgae were evaluated for their antioxidant properties and lipid composition. Both lipophilic (L) and
hydrophilic (H) oxygen radical absorbance capacity (ORAC) values were measured. Among the tested microalgae, the marine
microalga Nannochloropsis granulata showed the highest total ORAC value at 6948 μmol TE (100 g)
−1
,followedbythe
freshwater species Neochloris oleoabundans at 4508 μmol TE (100 g)
−1
and Scenedesmus obliquus at 4406 μmol TE
(100 g)
−1
of algal biomass. Freeze-dried algal biomass was also examined for lipid content by the Folch method. Lipid content
ranged from 30.9 to 49.3% and linear regression analysis revealed a statistically significant correlation between the lipid content
and the ORAC values. Tested microalgae showed moderate and dose-dependent DPPH radical scavenging activity. The total
phenol assay shows that marine microalga Tetraselmis chui had the highest phenolic content at 57.5 μmol GAE g
−1
and N.
oleoabundans had the lowest at 26.6 μmol GAE g
−1
of MeOH extract. A statistically significant correlation was detected between
DPPH radical scavenging activity and the phenolic content. Fatty acid analysis revealed that polyunsaturated fatty acids constituted
> 45% of the total fatty acid content in N. oleoabundans, Phaeodactylum tricornutum, Porphyridium aerugineum, S. obliquus,and
Scenedesmus sp. Total carotenoid concentration ranged from 1.1 to 29.5 mg g
−1
of dry algal biomass. Lutein, zeaxanthin, and β-
carotene are common carotenoids found in most of the algae tested. P. tricornutum contains significant amount of fucoxanthin at
24.3 mg g
−1
algal biomass. These carotenoids also contributed to the overall antioxidative activity of microalgae.
Keywords Microalgae
.
ORAC
.
Total phenolic
.
DPPH radical
.
Fatty acids
.
Carotenoids
Introduction
Microalgae are a diverse group of unicellular, primarily aquat-
ic organisms capable of performing photosynthesis. Because
some species are capable of producing high level of lipid,
these microscopic organisms are considered as a potential
source of bio-fuel (Spolaore et al. 2006). Marine species in
particular have an added potential advantage if they are devel-
oped as an energy crop that can be grown in salt water which
covers almost two thirds of the Earth’s surface. Microalgae are
also known to produce other high-value products including
pigments, proteins, polysaccharides, and omega-3 fatty acids
(Spolaore et al. 2006; Gantar and Svirčev 2008).
Haematococcus pluvialis has been commercialized for
production of the valuable carotenoid pigment astaxanthin
and Dunaliella salina for β-carotene (Borowitzka 2013).
Free radicals including reactive oxygen species (ROS) and
reactive nitrogen species (RNS) are generated during normal
cellular metabolism. These free radicals are highly reactive spe-
cies and play a dual role in humans as both beneficial and toxic
compounds depending on their concentration. At low or mod-
erate concentration, these reactive species exert beneficial ef-
fects on cellular redox signaling and immune function. At high
concentration, however, these radical species produce oxidative
stress, a harmful process that can lead to cell death through
oxidation of protein, lipid, and DNA (Pham-Huy et al. 2008;
Sen and Chakraborty 2011). Antioxidants are a crucial defense
against free radical-induced damage (Sen and Chakraborty
2011). Several natural compounds such as vitamin C, tocoph-
erol, and numerous plant extracts have been commercialized as
natural antioxidants to fight against oxidative stress associated
with various chronic diseases including atherosclerosis, diabe-
tes mellitus, neurodegenerative disorders, and certain types of
cancer (Pham-Huy et al. 2008; Vadlapudi 2012).
Even though microalgae are a rich source of bioactive mol-
ecules, only a limited number of studies have been performed
to explore the correlation of antioxidant activity and lipid
* Arjun H. Banskota
Arjun.Banskota@nrc-cnrc.gc.ca
1
Algal Carbon Conversion Flagship Program, Aquatic and Crop
Resource Development, National Research Council Canada, 1411
Oxford Street, Halifax, Nova Scotia B3H 3Z1, Canada
Journal of Applied Phycology
https://doi.org/10.1007/s10811-018-1523-1
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