Diversity, antibacterial and antioxidant activities of the fungal endophytes associated with Schleichera oleosa (Lour.) Merr

Abstract

Endophytic fungi were isolated from leaf, bark, inflorescence, fruit and seed of medicinal plant Schleichera oleosa found in the Western Ghats region of Karnataka, India. The endophytic fungal occurrence was studied by isolating them on potato dextrose agar (PDA) medium, malt extract agar (MEA) medium and moist blotter (MB) and species richness and evenness of endophytic fungi were determined by diversity and evenness indices. Fungal isolates were characterized morphologically into 84 species from 34 genera of 18 families and 9 morphotypes of which Alternaria alternata, Arcopilus cupreus, Aspergillus niger and Corynespora cassiicola were dominant. The colonization frequency was high in leaf in the winter season on the PDA medium. The four fungal isolates A. cupreus, C. cassiicola, Phomopsis liquidambaris and Setosphaeria rostrata that showed antibacterial activity were characterized by ITS1–5.8s-ITS4 regions of rDNA. A. cupreus expressed high antibacterial and antioxidant activities by agar-well diffusion and cyclic voltammetry methods, respectively. The metabolite extracted in ethyl acetate inhibited all the tested bacterial strains. Antioxidant activity of the extract was revealed the high redox potential. The orbitrap high-resolution LC-MS was used for metabolite profiling. The ethyl acetate extract of A. cupreus yielded a large number of bioactive compounds such as [(3-Oxo-2-butanyl) sulfanyl]-3-phenyl-4(3H)-quinazolinone, quercetin, caffeic acid, isofraxidin, and citric acid with diverse functions like antimicrobial, anti-inflammatory, antioxidant and anti-cancerous activities. Compounds with pesticidal and phytohormone activities and industrial importance were documented. Results of the present work indicated that A. cupreus could be a promising source of bioactive compounds with a wide range of applications.