In the search for safe and effective natural antioxidants, this study investigates the antioxidant and cytotoxic properties of aqueous extracts obtained from three fungi of the family Hymenochaetaceae: Inonotus sp., Fulvifomes sp., and Phylloporia boldo, all associated with endemic trees of the Chilean sclerophyll forest. Antioxidant capacity was assessed through DPPH, ABTS, and hydroxyl radical scavenging assays. Fulvifomes sp. exhibited the highest antioxidant activity across all methods, which was consistent with its elevated polyphenol content. P. boldo, on the other hand, had the highest protein concentration but comparatively lower antioxidant activity. Cytotoxicity was evaluated using the WST-1 assay in the RTgill-W1 salmonid cell line, revealing that Inonotus sp. displayed the lowest cytotoxicity at both tested concentrations, suggesting it may be suitable for bioactive applications in aquaculture. In contrast, Fulvifomes sp. and P. boldo showed significant cytotoxic effects at higher concentrations. These findings highlight the potential of Inonotus sp. as a natural antioxidant with low cytotoxicity and encourages further exploration of native forest fungi as sources of functional bioactive compounds for food, nutraceutical, or aquaculture applications.

Peptides designed to interfere with specific steps of viral infection mechanisms have shown promising antiviral potential. In this study, we investigated the ability of a synthetic peptide (peptide 303), derived from the fusion protein sequence of the Infectious Salmon Anemia Virus (ISAV), to inhibit membrane fusion mediated by the ISAV fusion peptide (ISAV-FP1). To assess this, we employed a model membrane system consisting of large unilamellar vesicles (LUVs) composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), dipalmitoylphosphatidylcholine (DPPC), and cholesterol. Membrane fusion kinetics were monitored via R18 fluorescence dequenching. Additionally, the interaction of peptide 303 with lipid membranes was evaluated using fluorescence anisotropy measurements. The potential direct interaction between peptide 303 and ISAV-FP1 was further examined through Förster Resonance Energy Transfer (FRET) assays. Our results demonstrate that peptide 303 effectively inhibits ISAV-FP1-mediated membrane fusion. Furthermore, peptide 303 was shown to interact with lipid bilayers and with ISAV-FP1 itself. These findings suggest a dual inhibitory mechanism in which peptide 303 both prevents ISAV-FP1 binding to the membrane and directly interacts with the fusion peptide, thereby disrupting its fusogenic activity.