Work

Bioprospecting nonpolar solvent extracts’ from Scadoxus multiflorus (Martyn) Raf. for antibacterial activity against fish pathogenic bacteria

Year: 2025

Type: article

Abstract: The rising global threat of antibiotic resistance has necessitated the exploration of alternative antimicrobial agents, particularly from plant-based sources. In this study, the Scadoxus multiflorus , an ornamental plant of the family amaryllidaceae was selected, known for its pharmacologically active bulbous alkaloids. The literature study revealed a complete lack of any scientific evidances of antibacterial potential of leaf extracts of this plant. Therefore, the antibacterial efficacy of Scadoxus multiflorus leaf extracts against several gram-negative fish pathogenic bacteria was explored. To screen the antibacterial potential different types of extraction processes such as soxhlet, cold and hot extraction methods were performed by the solvents of different polarities and five fish pathogenic bacterial strains ( Aeromonas hydrophila , A. veronii , A. salmonicida , Pseudomonas putida , and P. fluorescens ) were selected. The extracts were prepared through sequential fractionation using solvents of increasing polarity (hexane, chloroform, ethyl acetate, and methanol) by the soxhlet extraction method, and chloroform was selected for cold extraction method and distilled water was selected for the hot extraction method. The hexane extract (HESM) (MIC 0.500 mg mL −1 ) of S. multiflorus (HESM) demonstrated significant antibacterial activity against all of the tested bacterial strains in all of the performed assays (agar well diffusion, microbroth dilution, growth curve analysis, scanning electron microscope. Notably, while the standard antibiotic tetracycline showed limited efficacy against some of these pathogens, HESM exhibited significant inhibitory activity ( p < 0.0001). The maximum potency was observed against A. veronii . Hence these findings highlight the non-polar solvent hexane as the most suitable for accumulation of antibacterial activity producing phytochemicals in S. multiflorus for the first time and explores a new way for further investigation on the detection and isolation of bioactive phytochemicals and their application in aquaculture and antibacterial drug development. This study also set new direction for the testing of hexane extract against more bacterial strains including human pathogenic strains. • Sequential extraction from Scadoxus multiflorus leaves revealed strong antibacterial potential in the hexane extract. • Hexane extract showed significant activity against gram-negative fish pathogens, especially Aeromonas veronii . • HESM maintained a consistent MIC value of 0.500 mg/mL in both agar diffusion and broth dilution assays. • Bacterial growth curve analysis confirmed time-dependent suppression of A. veronii by HESM. • SEM analysis revealed structural damage to bacterial cells treated with HESM, supporting its antibacterial mechanism. • This is the first study report of use of non-polar solvents for isolating antibacterials from leaf extracts of S. multiflorus .

Source: The Microbe

DOI: 10.1016/j.microb.2025.100543