Tetradesmus obliquus organic extracts with antibacterial and antileishmanial activities

Abstract

Current treatments for leishmaniasis often result in side effects and bacterial infections that inhibit the healing of skin lesions, inducing a need to find new natural therapies. Microalgal bioactives can offer a potential alternative for treating leishmaniasis. This work aimed to evaluate the extraction yield from Tetradesmus obliquus microalgae using three different solvents (hexane, ethyl acetate, and ethanol), as well as to determine fatty acid profile, antibacterial and antileishmanial activities (Leishmania braziliensis promastigote), and cytotoxicity on human peripheral blood mononuclear cells (PBMC). In the first extraction, hexane achieved the highest yield (3.50 %) while ethanol was the most efficient solvent in the second extraction (4.47 %). The predominant fatty acids were palmitic acid (18.7 % to 20.6 %) and α-linolenic acid (15.4 % to 19.9 %). The ethanolic extract exhibited activity against S. aureus, E. coli, and K. pneumoniae as well as antileishmanial activity against L. braziliensis (IC₅₀ = 75 μg mL⁻¹), outperforming the reference drug meglumine antimoniate (Sb^V; IC₅₀ of 119.76 μg mL⁻¹). The extract showed no cytotoxicity to PBMCs at the tested concentrations (CC₅₀ > 250 μg mL⁻¹) and exhibited a selectivity index (SI >3.33) comparable to Sb^V (SI > 3.44). In conclusion, the ethanolic extract of T. obliquus emerges as a promising candidate for novel therapies against skin bacteria and American Tegumentary Leishmaniasis (ATL).