Evaluation of Antibacterial and Antifungal activities of Helianthus annuus Leaf Extracts Against Selected Fish Pathogens

ABSTRACT Medicinal plants serve as an important source of bioactive compounds that can be used to combat microbial infections, especially given the rise in antimicrobial resistance. This study investigated the phytochemical makeup and the in vitro antibacterial and antifungal properties of aqueous, ethanol, methanol, and petroleum ether extracts from the leaves of Helianthus annuus (sunflower) against certain fish and human pathogenic microorganisms. Initial qualitative phytochemical analysis identified a variety of secondary metabolites, such as alkaloids, flavonoids, phenols, steroids, terpenoids, saponins, tannins, proteins, carbohydrates, glycosides, oils, resins, and amino acids, with the methanolic extract showing the most diverse phytochemical content. The antibacterial effects were tested against Staphylococcus aureus, Proteus mirabilis, Escherichia coli, Klebsiella pneumoniae, and Salmonella paratyphi A, while the antifungal effects were assessed against Candida albicans, Aspergillus niger, Aspergillus flavus and Aspergillus fumigatus using the agar well diffusion technique. All extracts exhibited antimicrobial activity that increased with dosage, with the methanol leaf extract proving to be the most effective. Remarkably, the highest antibacterial activity was observed against P. mirabilis (46.67 ± 0.67 mm), and the most potent antifungal activity was against A. niger (31 ± 0.58 mm) at a concentration of 500 µl. These results suggest that H. annuus leaves, particularly the methanolic extracts, have significant antibacterial and antifungal potential, which supports their traditional use and indicates their potential as a natural source for developing environmentally friendly antimicrobial agents.