AUTHOR=Kejžar Jan , Jagodic Hudobivnik Marta , Nečemer Marijan , Ogrinc Nives , Masten Rutar Jasmina , Poklar Ulrih Nataša 

TITLE=Characterization of Algae Dietary Supplements Using Antioxidative Potential, Elemental Composition, and Stable Isotopes Approach

JOURNAL=Frontiers in Nutrition

VOLUME=7

YEAR=2021

URL=https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2020.618503

DOI=10.3389/fnut.2020.618503

ISSN=2296-861X

ABSTRACT=<p>Dietary supplements based on algae, known for their nutritional value and bioactive properties, are popular products among consumers today. While commercial algal products are regarded safe by numerous studies, information about the production and origin of such products is scarce. In addition, dietary supplements are not as strictly regulated as food and medicinal drugs. We characterized different algal products (kelps: Laminariales, <italic>Spirulina</italic> spp., <italic>Chlorella</italic> spp., and <italic>Aphanizomenon flos-aquae</italic>), obtained on Slovenian market, based on their elemental composition (X-ray fluorescence, inductively coupled plasma–mass spectrometry), antioxidative potential [DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, total phenolic content], and stable isotope values [carbon (C), nitrogen (N), and sulfur (S); elemental analyzer isotope ratio mass spectrometry (EA-IRMS) method]. Antioxidative potential is consistent among products of the same type, with <italic>A. flos-aquae</italic> samples having 4.4 times higher antioxidative potential compared to <italic>Chlorella</italic> spp. and 2.7 times higher compared to <italic>Spirulina</italic> spp. Levels of toxic trace elements (arsenic, cadmium, mercury, and lead) are below the maximum allowed values and as such do not pose risk to consumers' health. Samples of <italic>Spirulina</italic> spp. have relatively high δ<sup>15</sup>N (7.4 ‰ ± 4.4‰) values, which indicate use of organic nitrogen sources in certain samples. Likewise, different elemental composition and isotopic ratios of stable elements (C, N, and S) for the samples with <italic>Spirulina</italic> spp. or <italic>Chlorella</italic> spp. are the consequence of using different nutrient sources and algae-growing techniques. Statistical analysis (principal component analysis) has confirmed that all tested <italic>A. flos-aquae</italic> samples originate from the same source, supposedly Klamath Lake (Oregon, USA). Hawaiian <italic>Spirulina pacifica</italic> can also be differentiated from all the other samples because of its characteristically high metal content (iron, manganese, zinc, cobalt, nickel, vanadium). <italic>Chlorella</italic> spp. and <italic>Spirulina</italic> spp. require further analyses with larger number of samples, as differentiation is not possible based on results of this study.</p>