Evaluation of Antioxidant Potential, DNA Damage Protection and Anticancer Activities of Three Endophytic Fungi Associated with Selected Medicinal Plants

Author(s): Rashmi Mishra, Jai Shanti Kushveer, Mohd. Imran K. Khan and Vemuri Venkateswara Sarma

Abstract: Background: Endophytic fungi refer to such microbes that colonize inside the plant tissues without causing any disease/symptoms. Endophytic fungi associated with medicinal plants often are reported to be an interesting source of bioactive compounds. In this study, we selected three potential endophytic fungi viz. Daldinia eschscholtzii (TP2-6), Daldinia placentiformis (CP2-11) and Alternaria alternata (CPR-9) to evaluate their antioxidant and anticancer potential. Objective: The aim of this study was to assess the polyphenol contents, antioxidant capacity of selected endophytic fungi isolated from leaves of Carica papaya and Tridax procumbens using different assays. Furthermore, DNA damage protection ability and anticancer potential against human cancer cell lines was also investigated. Method: Secondary metabolites present in the crude extracts, obtained through ethyl acetate extraction of 20 different endophytic fungi were screened for the presence of phyto-constituents, Total phenolic content (TFC), Total flavonoid content (TFC) and antioxidant potential using 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay, 2,2′-azinobis(3-ethylbenzothiazoline- 6-sulfonic acid) di-ammonium salt (ABTS) assay, nitric oxide (NO) radical scavenging activity, hydrogen peroxide (H2O2) free radical scavenging assay, reducing power assay, DNA damage protection and anticancer potential. Results: Phenols, tannins, cardic glycosides, saponins, alkaloids and flavonoids were the main phyto-constituents present in the endophytic fungi. Of the 3 endophytic fungi, Daldinia placentiformis (CP2-11) showed the highest TPC and TFC with a value of 118.64±4.61μg GAE (gallic acid equivalent) /mL of crude and 164.87±6.58 μg QE (quercetin) /mL of crude, respectively, while its antioxidant activity for DPPH free radical scavenging assay was 85.02±0.87%. A high positive linear correlation was found between the IC50 values of antioxidant activities and phenolic and flavonoid contents r = 0.9158; R2 = 0.8388 and r = 0.9886; R2 = 0.9775. Endophytic fungal isolates, Daldinia placentiformis (CP2-11) and Daldinia eschscholtzii (TP2-6) showed significant DNA damage protection and antioxidant activity in different assays. Conclusion: The present study suggests that endophytic fungi associated with medicinal plants could be a potential source of novel natural antioxidant and anticancer compounds.

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