Secondary metabolites of cyanobacteria from Cape Verde Archipelago act as NO donors with potential application in dermatology and cosmetics

Nitric oxide (NO) is a versatile mediator implicated in a variety of physiological processes, with the ultimate goal of maintaining organism homeostasis. In the present work, aqueous extracts from ten cyanobacteria strains isolated from the Cape Verde archipelago were explored as potential NO donors. None of the strains are toxin producers, as demonstrated by PCR and LC-MS analysis. The extracts were mainly composed by phycobiliproteins (9.1 to 43.8 %), followed by polysaccharides (7.7 to 35.1 %), phenols (1.49 to 3.3 %) and chlorophylls (0 to 0.45 %). All the extracts revealed antioxidant potential, with Salileptolyngbya sp. LEGE 181184 presenting the lowest IC₅₀ value for superoxide anion radical scavenging (46.50 μg mL⁻¹), and ability to inhibit the pro-inflammatory enzyme lipoxygenase (LOX), Salileptolyngbya sp. LEGE 181150 presenting an IC₂₅ similar to the positive control quercetin (28.49 and 31.77 μg mL⁻¹, respectively), highlighting the potential of cyanobacteria extracts as natural ingredients for LOX inhibition. All the extracts were able to increase the NO produced by the macrophage cell line RAW 264.7 through iNOS modulation (from concentrations starting in 12.5 μg mL⁻¹), in a similar mechanism and superior extend to that of LPS. None of the extracts induced cytotoxicity to RAW 264.7 cells and to the endothelial hCMEC/d3, the fibroblast 3 T3/L1 and the keratinocytes HaCaT cell lines, and no environmental hazard is predicted, as demonstrated through the zebrafish (Danio rerio) embryo acute toxicity test (zFET). This pioneer study points-out cyanobacteria aqueous extracts as innovative and biobased natural antimicrobial ingredients which, through a NO-donating mechanism, may potentially act against important antibiotic-resistant strains, thus being worth of consideration as therapeutic agents in dermatology.