Abstract

Background: Endophytic fungi are microorganisms that colonize inside the plant tissues without causing any disease symptoms. Endophytic fungi isolated from medicinal plants have emerged as an interesting source for the isolation of bioactive compounds. In this study, we selected Calotropis procera, a member of the Asclepiadaceae family commonly called ‘Aak’ to evaluate the antioxidant potential of isolated endophytic fungi.

Objective: The aim of this study was to assess the total phenolic content (TPC), antioxidant capacity by using different assay and phytochemical screening of endophytic fungi isolated from Calotropis procera (leaves, stem and root).

Method: Crude ethyl acetate extracts of 20 different endophytic fungi isolated from Calotropis procera were tested for their preliminary phytoconstituents presence, TPC estimation (by Folin–Ciocalteu colorimetric assay) and antioxidant potential [1, 1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay, hydrogen peroxide (H2O2) free radical scavenging assay, β-carotene-linoleic free radical scavenging assay, metal chelating assay and xanthine oxidase inhibitory assay].

Results: Phenols, carbohydrates, saponins, tannins, alkaloids and flavanoids were the main phytoconstituents present in the endophytic fungi. Among the endophytes, Aspergillus nomius showed the highest TPC [72.71±1.67 µg GAE (gallic acid equivalent) /mg dry weight of fungi] and antioxidant activity for DPPH free radical scavenging assay (68.86±0.19%). A high positive linear correlation was found between TPC and xanthine oxidase inhibitory assay (R2-0.890) and between TPC and DPPH free radical scavenging assay (R2-0.839). Aspergillus and Fusarium genus species showed significant antioxidant activity by the different assay.

Conclusion: The present study revealed some endophytic fungi from Calotropis procera could be a potential source of novel natural antioxidant compounds.

Keywords: Antioxidant activity, Calotropis procera, DPPH assay, Endophytic fungi, Total phenolic content, Xanthine oxidase inhibitory assay.