Protective Effects on Keratinocytes by Extracts Enriched in Polysaccharides from Limnospira platensis Grown Under Autotrophic and Mixotrophic Conditions

<b>Background/Objectives:</b> Natural polysaccharides have many bio-pharmacological effects, which make them compounds with potential in healthcare. <i>Limnospira platensis</i> (Spirulina), a well-known blue-green cyanobacterium with relevance in the market of nutraceuticals, produces polysaccharides with recognized antioxidant and anti-inflammatory activities. Noteworthy, the growth of the cyanobacterium biomass may be obtained in a more sustainable manner under mixotrophic conditions. In the present study, we compared the antioxidant and anti-inflammatory effects of polysaccharide-enriched extracts from the cyanobacterium cultured under autotrophism (Auto-P extract) or mixotrophism (Mixo-P extract); this latter was realized using medium added with brewery wastewater (BWW). <b>Methods and Results:</b> Non-cellular investigation showed a better antioxidant profile for Mixo-P extract in the OH radical scavenging assay and a similar activity between the extracts in ABTS and ferrous chelation assays. The antioxidant protective activity of <i>L. platensis</i> extracts investigated on HaCat cells in the range of 0.3-10 μg/mL (not cytotoxic concentrations), against hydrogen peroxide (H₂O₂, 600 μM)-induced damage, revealed a similar activity by the two extracts. When tested against the inflammatory stimuli with lipopolysaccharide (LPS, 10 μg/mL) or tumor necrosis factor-α (TNF-α, 10 ng/mL), both Auto-P and Mixo-P showed an ability to prevent the effects of the inflammatory agents on cell viability and on interleukin-1β (IL-1β) and interleukin-6 (IL-6) release, with a slightly greater potency by Mixo-P extract. <b>Conclusions:</b> In conclusion, our data suggest the possible use of <i>L. platensis</i> polysaccharide-enriched extracts in biological-made pharmaceuticals for skin disorders or in cosmeceuticals. In addition, this study demonstrates that mixotrophic cultivation of <i>L. platensis</i> may be an alternative and sustainable way for biotechnological applications of the cyanobacterium biomass.