A novel source of the cardiac glycoside digoxin from the endophytic fungus Epicoccum nigrum: isolation, characterization, production enhancement by gamma irradiation mutagenesis and anticancer activity evaluation.

AIMS: Different endophytic fungi were isolated and screened for their digoxin-producing ability. Strain improvement and different culture conditions were studied for more effective production of digoxin. METHODS AND RESULTS: Among the isolated fungi, an isolate produced digoxin in a concentration of 2·07 mg l-1 . The digoxin-producing fungal isolate was identified as Epicoccum nigrum Link according to the morphological features and phylogenetic analyses. The potentiality of the fungal strain for production enhancement of digoxin was performed by gamma radiation mutagenesis. Gamma irradiation dose of 1000 Gy intensified the digoxin yield by five-fold. Using this dose, a stable mutant strain with improved digoxin productivity was isolated and the stability for digoxin production was followed up across four successive generations. In the effort to increase digoxin magnitude, selection of the proper cultivation medium, addition of some elicitors to the most proper medium and several physical fermentation conditions were tested. Fermentation process carried out in malt extract autolysate medium (pH 6·5) supplemented by methyl jasmonate and inoculated with 2 ml of 6-day-old culture and incubated at 25°C for 10 days stimulated the highest production of digoxin to attain 50·14 mg l-1 . Moreover, cytotoxicity of digoxin separated from the fungal culture was tested against five different cancer cell lines. Based on the MTT assay, digoxin inhibited the proliferation of the five different cancer cell lines and the recorded 50% inhibitory concentration ranged from 10·76 to 35·14 µg ml-1 . CONCLUSIONS: This is the first report on the production and enhancement of digoxin using fungal fermentation as a new and alternate source with high productivity. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings offer new and alternate sources with excellent biotechnological potential for digoxin production by fungal fermentation. Moreover, digoxin proved to be a promising anticancer agent whose anticancer potential should be assessed in prospective cancer therapy.

Biosynthesis of zinc oxide nanoparticles with antimicrobial, anticancer, antioxidant and photocatalytic activities by the endophytic Alternaria tenuissima.

AIMS: Zinc oxide nanoparticles (ZnONPs) were successfully synthesized using the culture filtrate of the endophytic fungus Alternaria tenuissima as a rapid, eco-friendly and cost-effective method. METHODS AND RESULTS: The rapid synthesis of ZnONPs was completed after 20 min as confirmed by UV-Vis spectroscopy. The synthesized ZnONPs showed a single-phase crystalline structure. Dynamic light scattering analysis showed that the synthesized ZnONPs were monodispersed and the recorded polydispersity index value was 0·311. Zeta potential value of -23·92 mV indicated the high stability of ZnONPs. Transmission electron microscope revealed the spherical shape and the mean particle size was 15.45 nm. Functional groups present in the prepared samples of ZnONPs were confirmed by Fourier transform infrared spectroscopy. Additionally, the biological activities of in vitro antimicrobial, anticancer, antioxidant as well as the photocatalytic activities were evaluated. ZnONPs showed broad spectrum of antimicrobial potential against all the tested plant and human pathogens. Based on the MTT assay, ZnONPs inhibited the proliferation of normal human melanocytes, human breast and liver cancer cell lines with IC50 concentrations of 55·76, 18·02 and 16·87 µg ml-1 . ZnONPs exhibited promising antioxidant potential with 50% inhibitory concentration of 102·13 µg ml-1 . Moreover, ZnONPs showed efficient degradation of methylene blue dye. CONCLUSIONS: The synthesized ZnONPs showed promising activities that can be better explored in the near future for many medical, agricultural and industrial applications. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests a new and alternate approach with the excellent biotechnological potentiality for the production of ZnONPs which could open up the way for the industrial manufacture of nanoparticles using microbial platforms.