Isolation, identification, and bioactivity evaluation of endophytic fungi from Ruta graveolens: insights into antimicrobial and antioxidant potential.

Abstract

This study presents a comprehensive investigation of endophytic fungi isolated from Ruta graveolens (Rutaceae), evaluating the bioactivity of their extracts in terms of antimicrobial and antioxidant properties, along with preliminary mycochemical profiles. Twenty-seven isolates were identified using morphological and molecular identification (ITS-rDNA sequencing). Phylogenetic analysis classified them into Alternaria (66.7%, dominant in stems), Chaetomium (25.9%, prevalent in leaves), Achaetomium (3.7%), and Stagonosporopsis (3.7%) genera, demonstrating strong tissue specificity. Antibacterial screening (disk diffusion) of the fungal extracts revealed that 52% (14/27) were active; extracts of S4, S9, S20-2, and L11 showed inhibition against Staphylococcus aureus (inhibition zones, 14.5-15.8 mm at 100 mg/mL), while L5, L10, and L11 extracts exhibited dual activity against both S. aureus and Escherichia coli. Antifungal assays of the extracts identified strains S22, L5, and L12 as effective against phytopathogens Alternaria alternata, Pyricularia grisea, and Curvularia lunata (inhibition rates, 54.2-67.5% at 1 mg/mL). Meanwhile, antioxidant evaluation of the extracts highlighted strain L11 for remarkable DPPH and ABTS radical scavenging (IC₅₀, 8 μg/mL and 5 μg/mL, respectively). Qualitative mycochemical analysis linked ubiquitous coumarins/phenols to broad antibacterial activity. Alkaloids uniquely correlated with E. coli inhibition (L5, L10, L11), while terpenoids/steroids (S9, S20-2) specifically enhanced anti-S. aureus activity. These findings underscore R. graveolens-associated endophytes as potential sources of antimicrobial and antioxidant metabolites, suggesting possible applications for pharmaceutical development and sustainable agricultural applications.