Cytotoxic and antibacterial naphthoquinones from an endophytic fungus, Cladosporium sp

Md Imdadul Huque Khan; Md Hossain Sohrab; Satyajit Roy Rony; Fakir Shahidullah Tareq; Choudhury Mahmood Hasan; Md Abdul Mazid

doi:10.1016/j.toxrep.2016.10.005

Cytotoxic and antibacterial naphthoquinones from an endophytic fungus, Cladosporium sp

Toxicol Rep. 2016 Oct 19:3:861-865. doi: 10.1016/j.toxrep.2016.10.005. eCollection 2016.

Authors

Md Imdadul Huque Khan¹, Md Hossain Sohrab², Satyajit Roy Rony², Fakir Shahidullah Tareq³, Choudhury Mahmood Hasan¹, Md Abdul Mazid¹

Affiliations

¹ Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Dhaka, Dhaka 1000, Bangladesh.
² BCSIR Laboratories Dhaka, Dr. Qudrat-I-Khuda Road, Dhanmondi, Dhaka 1205, Bangladesh.
³ Korea Ocean Research & Development Institute (KORDI), Ansan, Geonggi-Do, South Korea.

Abstract

Objective: Endophytes have the potential to synthesize various bioactive secondary metabolites. The aim of the study was to find new cytotoxic and antibacterial metabolites from endophytic fungus, Cladosporium sp. isolated from the leaves of Rauwolfia serpentina (L.) Benth. ex Kurz. (Fam: Apocyanaceae).

Materials and methods: The endophytic fungus was grown on potato dextrose agar medium and extracted using ethyl acetate. Secondary metabolites were isolated by chromatographic separation and re-crystallization, and structures were confirmed by ¹H NMR, ¹³C NMR and mass spectroscopic data. The cytotoxicity was determined by WST-1 assay and brine shrimp lethality bioassay, while antibacterial activity was assessed by disc diffusion method.

Results: Two naphthoquinones, namely anhydrofusarubin (1) and methyl ether of fusarubin (2), were isolated from Cladosporium sp. The isolated compounds 1 and 2, by WST-1 assay against human leukemia cells (K-562) showed potential cytotoxicity with IC₅₀ values of 3.97 μg/mL and 3.58 μg/mL, respectively. Initial screening of crude ethyl acetate extract and column fractions F-8 and F-10 exhibited noticeable cytotoxicity to brine shimp nauplii with LC₅₀ values of 42.8, 1.2 and 2.1 μg/mL, respectively. Moreover, the isolated compound 2 (40 μg/disc) showed prominent activities against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Bacillus megaterium with an average zone of inhibition of 27 mm, 25 mm, 24 mm and 22 mm, respectively and the activities were compared with kanamycin (30 μg/disc).

Conclusion: Our findings indicate that anhydrofusarubin (1) and methyl ether of fusarubin (2) might be useful lead compounds to develop potential cytotoxic and antimicrobial drugs.

Keywords: Anhydrofusarubin (PubChem CID: 157509); Antibacterial activity; Cladosporium species; Cytoxicity; Endophytic fungi; Fusarubin; Hydrogen Peroxide (PubChem CID: 784); Methyl ether of fusarubin (PubChem CID: 14050831); Triton X-100 (PubChem CID: 5590).