Secondary Metabolites from Diaporthe eres SK3, an Endophytic Fungus of Sellaginella kraussiana Sw. Collected from the Northeast Indian Hills, Exhibits Potential in Vitro Bioactivities.

Endophytic fungi are vital producers of novel, pharmaceutically active metabolites and are reshaping the research landscape on natural products. Here, an endophytic fungus, Diaporthe eres SK3, was isolated from Selaginella kraussiana Sw., collected from the forests of Arunachal Pradesh, and produces antimicrobial and antioxidative metabolites. Chemo-profiling of the SK3 metabolites using column chromatographic and spectroscopic techniques reveals the presence of isovaleric acid, benzyl alcohol, dibutyl phthalate, phenethylamine, and 2,4-di-tert-butylphenol. Killing kinetics assays confirmed the microbicidal activity of this metabolite against a panel of microbes, including MRSA, Candida albicans, and Candida tropicalis, with a Minimum Microbicidal Concentration (MMC) of 12.5-350 µg mL- 1. The treated microbial cells experience a lethal leakage of major macromolecules and a significant blockage of enzymes involved in biochemical events. Additionally, the post-SK3 EA extract treatment confirms the prolonged blockage of the growth of C. albicans and MRSA. These metabolites function synergistically with ciprofloxacin and exhibit MRSA-induced clot lysis activity. In silico analysis reveals the binding affinities of the identified metabolites for Penicillin Binding Protein 2a (PDB ID: 1MWT), the MRSA receptor, which is the probable cause of the anti-MRSA activity. The metabolites also exhibited radical scavenging activity with an IC50 of 81.36 ± 0.27-117.03 ± 1.20 µg mL- 1 against DPPH and ABTS free radical generators, respectively. The present investigative outcomes suggest that metabolites from the endophytic fungus Diaporthe eres SK3 exhibit broad-spectrum in vitro bioactivities.