On the Antimicrobial Potential of Asparagopsis armata's Ethanol Extract: A New Multiple-Industry Bio-Product?

The identification and development of novel antimicrobials is a crucial challenge in the face of increasing antibiotic and antimycotic resistance. As such, there is growing interest in exploring the chemical diversity of natural sources, such as invasive seaweeds such as Asparagopsis armata. The valorization of such sources can further contribute to the development of bio-based industries, aligning with societal goals for environmental and economic sustainability. Therefore, a solid-liquid extraction method was performed using ethanol, and the obtained extract was studied for chemical composition elucidation, bioactivity, and toxicity evaluation. Analysis by GC-MS revealed some major chromatographic peaks, including floridoside (2-α-O-D-galactopyranosyl glycerol), glycerol, and oleamide. Also, several other smaller peaks were tentatively attributed to Low Molecular Weight Carbohydrate Derivatives, including isosaccharino-1,4-lactone, which had only been reported once in nature. The extract demonstrated significant antioxidant activity as measured by Ferric Reducing Antioxidant Potential and Oxygen Radical Absorption Capacity, but not by Lipid Peroxidation Inhibitory Potential assays, which is in line with its polar nature. The extract exhibited antimicrobial activity against various microorganisms, with a MIC of 2 mg/mL observed for Staphylococcus epidermidis, Vibrio parahaemolyticus, and the three yeast strains tested. Moreover, the extract inhibited the growth and phenotypic changes in filamentous fungi, which may result in reduced virulence. Specifically, the extract inhibited sporulation in Aspergillus fumigatus and orange pigmentation in Fusarium graminearum, possibly by a reduction in the production of aurofusarin, rubrofusarin, and mycotoxins. In vitro cell viability assays in 3T3, RAW264.7, and HaCaT demonstrated the extract was not cytotoxic or presented low cytotoxicity at concentrations up to 0.1 mg/mL, but a strong cytotoxic effect was observed at 1 mg/mL. At non-cytotoxic concentrations, the ethanol extract inhibited up to 48% of NO production in LPS-stimulated RAW264.7. This may indicate that anti-inflammatory activity may add to the antimicrobial activity in human and animal systemic and topical applications of the extract. In this work, new molecules were reported in A. armata, and the bioactivities reported were novel for this extract and algal species-especially through the choice of uncommon but very relevant pathogens to study. Our findings are a valuable contribution to addressing challenges in human and animal health, food and feed technology, as well as animal husbandry and agriculture.