Abstract
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, Spirulina spp., Chlorella spp., and Aphanizomenon flos-aquae), 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 A. flos-aquae samples having 4.4 times higher antioxidative potential compared to Chlorella spp. and 2.7 times higher compared to Spirulina 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 Spirulina spp. have relatively high δ15N (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 Spirulina spp. or Chlorella spp. are the consequence of using different nutrient sources and algae-growing techniques. Statistical analysis (principal component analysis) has confirmed that all tested A. flos-aquae samples originate from the same source, supposedly Klamath Lake (Oregon, USA). Hawaiian Spirulina pacifica can also be differentiated from all the other samples because of its characteristically high metal content (iron, manganese, zinc, cobalt, nickel, vanadium). Chlorella spp. and Spirulina spp. require further analyses with larger number of samples, as differentiation is not possible based on results of this study.
Highlights
There are numerous algae-based dietary supplements available on the market, which indicates their widespread use among consumers
Dietary supplements were selected based on several types of algae [kelps: Laminariales (n = 2), Spirulina spp. (n = 7), Chlorella spp. (n = 5), and AFA (n = 4)] with different types of production— conventional and organic
Average values of total phenolic content (TPC) of different dietary supplements based on algae, expressed as mg gallic acid equivalent (GAE)/g solid sample, were 12.3 ± 1.2 for samples of Chlorella spp., 23.2 ± 6.4 for Spirulina spp., 96.4 ± 7.5 for AFA, and 1.6 ± 1.6 for kelp (Figure 1)
Summary
There are numerous algae-based dietary supplements available on the market, which indicates their widespread use among consumers. Dietary supplements are not subject to strict regulations like drugs and imported food. Microalgae (unicellular eukaryotes and cyanobacteria) are interesting organisms to cultivate because of their ability to synthesize bioactive compounds and accumulate minerals and high nutritional value. They are able to grow in modified mediums, including wastewater, which improves economic viability of cultivating microalgae [1]. Production share of food/feed microalgae products owned by European companies is estimated to be approximately 5% of the global market [2]
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