Amazonian Cyanobacteria as a Source of Bioactive Compounds With Antimicrobial and Cytotoxic Properties

Cyanobacteria are photosynthetic microorganisms known for producing diverse bioactive compounds. This study explores the bioactivity of extracts and fractions from Amazonian cyanobacteria and their pigment and phenolic compound production. A fraction from Synechococcus sp. CACIAM 05 showed cytotoxicity against hCMEC/D3 and MG‐63 cells. UPLC‐HRMS/MS analysis of this fraction (C5FD) identified pheophytin and phorbide derivatives as key bioactive molecules. In antimicrobial assays, another fraction from the same strain exhibited bactericidal activity against Bacillus subtilis ATCC 6633, with a MIC of 40 µg mL −1 . Additional strains also showed antibacterial effects, though with higher MICs. Allelopathic activity identified eleven bioactive strains, including a synergistic effect between Desmonostoc sp. CACIAM 45 and Synechocystis sp. CACIAM 05. Aqueous extracts from Lyngbya sp. CACIAM 07 and Desmonostoc sp. CACIAM 45 showed the highest total phenolic content. Cultivation of Desmonostoc sp. CACIAM 45 in different media indicated CHU‐10 and ASM as optimal for phenolic and phycobiliprotein production. These findings contribute to the field by unveiling novel bioactivities and metabolic profiles of Amazonian cyanobacteria, supporting their potential as a valuable source of natural products for pharmaceutical and biotechnological applications.