Exploration of the chemical constituents and its antioxidant, antibacterial activities of endophytic fungi isolated from the medicinal plant Dillenia indica.

Abstract

Assam, India being the pool for ethnomedicinal plants harbors diverse endophytic fungi constituting major bioactive metabolites. The present study was designed to screen the antioxidant, antibacterial activities along with the chemical constituents of the endophytic fungi isolated from the fruits of Dillenia indica (commonly known as Otenga in Assam). Screening of such metabolic compounds and their antioxidant, antibacterial activities can have tremendous potential in suppressing certain diseases. Agar well diffusion method has been used to carry out the antibacterial assay against three pathogenic bacteria two gram positive [Bacillus subtilis (MTCC No. 441); Staphylococcus aureus (MTCC No. 740)] and one gram negative [Escherichia coli (MTCC No. 739)]. Aspergillus fumigatus of ethyl acetate extract showed a prominent activity against Staphylococcus aureus followed by Aspergillus flavus and Aspergillus niger. Antioxidants have the potential to neutralize and inhibit the action of free radicals. The highest scavenging activity was exhibited by ethyl acetate extract of Aspergillus fumigatus in DPPH assay. Furthermore, the phytochemical screening revealed the presence of flavonoids, alkaloids, terpenoids and saponins. Result showed that ethyl acetate extract of Aspergillus fumigatus showed the highest phenolic content (236.81 ± 0.2mg.g-1) and least was shown by Aspergillus flavus (92.12 ± 1.4mg.g-1). Total flavonoids content for Aspergillus fumigatus (39.08 ± 0.2mg.g-1) was found to be highest compared to other isolates. Molecular identification of the endophytic fungus showing highest activity was done based on 18S rRNA. The sequenced was submitted in Genbank with accession number MH540721 showing high similarities with Aspergillus fumigatus strain 3,162,954. A. fumigatus strain is subjected to GC/MS analysis that revealed the chemical constituents 2-isopropyl-5-methyl-1-heptanol, dodecane, 1-fluoro-pentanoic acid, 2-ethylhexyl ester, 1-octanol, 2-butyl-1-dodecanol. Thus, the present work reveals that endophytic fungi colonizing in ethnomedicinal plant Dillenia indica could be a promising source for antioxidant and antibacterial activity. Further work is needed to add value in various therapeutic and pharmaceutical fields.