Resistance to antifungal agents represents a major clinical challenge, leading to high morbidity and mortality rates, especially in immunocompromised patients. In this study, we screened soil bacterial isolates for the capability of producing metabolites with antifungal activities via the cross-streak and agar cup-plate methods. One isolate, coded S6, showed observable antifungal activity against Candida (C.) albicans ATCC 10231 and Aspergillus (A.) niger clinical isolate. This strain was identified using a combined approach of phenotypic and molecular techniques as Lysinibacillus sp. MK212927. The purified metabolite displayed fungicidal activity, reserved its activity in a relatively wide range of temperatures (up to 60 °C) and pH values (6–7.8) and was stable in the presence of various enzymes and detergents. As compared to fluconazole, miconazole and Lamisil, the minimum inhibitory concentration of the metabolite that showed 90% inhibition of the growth (MIC90) was equivalent to that of Lamisil, half of miconazole and one fourth of fluconazole. Using different spectroscopic techniques such as FTIR, UV spectroscopy, 1D NMR and 2D NMR techniques, the purified metabolite was identified as terbinafine, an allylamine antifungal agent. It is deemed necessary to note that this is the first report of terbinafine production by Lysinibacillus sp. MK212927, a fast-growing microbial source, with relatively high yield and that is subject to potential optimization for industrial production capabilities.

Background: This study aimed to produce, purify, structurally elucidate, and explore the biological activities of metabolites produced by Streptomyces (S.) griseus isolate KJ623766, a recovered soil bacterium previously screened in our lab that showed promising cytotoxic activities against various cancer cell lines. Methods: Production of cytotoxic metabolites from S. griseus isolate KJ623766 was carried out in a 14L laboratory fermenter under specified optimum conditions. Using a 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyl tetrazolium-bromide assay, the cytotoxic activity of the ethyl acetate extract against Caco2 and Hela cancer cell lines was determined. Bioassay-guided fractionation of the ethyl acetate extract using different chromatographic techniques was used for cytotoxic metabolite purification. Chemical structures of the purified metabolites were identified using mass, 1D, and 2D NMR spectroscopic analysis. Results: Bioassay-guided fractionation of the ethyl acetate extract led to the purification of two cytotoxic metabolites, R1 and R2, of reproducible amounts of 5 and 1.5 mg/L, respectively. The structures of R1 and R2 metabolites were identified as β- and γ-rhodomycinone with CD50 of 6.3, 9.45, 64.8 and 9.11, 9.35, 67.3 µg/mL against Caco2, Hela and Vero cell lines, respectively. Values were comparable to those of the positive control doxorubicin. Conclusions: This is the first report about the production of β- and γ-rhodomycinone, two important scaffolds for synthesis of anticancer drugs, from S. griseus.

Natural products particularly microbial metabolites have been the mainstay of cancer chemotherapy and are likely to provide many of the lead structures and derivatives with new biological activities. In this research, the production of some potential cytotoxic metabolites from Streptomyces (S.) griseus isolate KJ623766 was carried out in 14 L laboratory fermenter under specified optimum conditions (28°C temperature, 200 RPM rotation speed, uncontrolled PH, 3 vvm aeration and 2 bar airflow pressure). After 72 hrs of incubation, the cell free culture supernatant (CFCS) was collected and extracted using ethyl acetate (1:1, v/v) at pH 7.0. Using 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyl tetrazolium-bromide (MTT) assay, the cytotoxic activity of the ethyl acetate extract against Caco2 and Hela cancer cell lines was determined with CD50 of 14 µg/ml and 20 µg/ml, respectively. Bioassay guided fractionation of the ethyl acetate extract using different chromatographic techniques had led to the purification of the cytotoxic metabolites coded W1, R1 and R2 with reproducible amounts of 20, 5, and 1.5 mg/l, respectively. The structures of respective metabolites were determined based on the mass, 1D and 2D NMR spectroscopic analysis and were identified as genistein, β-rhodomycinone and γ- rhodomycinone, respectively. Accordingly, S. griseus isolate KJ623766 can be used as a potential industrial strain for the commercial production of the isoflavonoid genistein, as well as for the production of β-and γ- rhodomycinone to be used for the construction of new derivatives with more potent cytotoxic activities of the anthracycline family. To the best of our knowledge, this is the first report about the production of the isoflavonoid genistein by S. griseus KJ623766.

Natural products particularly microbial metabolites have been the mainstay of cancer chemotherapy and are likely to provide many of the lead structures and derivatives with new biological activities. In this research, the production of some potential cytotoxic metabolites from Streptomyces (S.) griseus isolate KJ623766 was carried out in 1 4 L laboratory fermenter under specified optimum conditions (28°C temperature, 200 RPM rotation speed, uncontrolled PH, 3 vvm aeration and 2 bar airflow pressure). Using 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyl tetrazolium-bromide (MTT) assay, the cytotoxic activity of the ethyl acetate (1:1, v/v) extract of cell free culture supernatant (CFCS) against Caco2 and Hela cancer cell lines was determined with CD 50 of 14 µg/ml and 20 µg/ml, respectively. Bioassay guided fractionation of the ethyl acetate extract using different chromatographic techniques had led to the purification of the cytotoxic metabolites coded W1, R1 and R2 with reproducible amounts of 20, 5, and 1.5 mg/l, respectively. The structures of respective metabolites were determined using various spectroscopic analysis and identified as genistein, β-rhodomycinone and γ- rhodomycinone, respectively. Accordingly, S. griseus isolate KJ623766 can be used as a potential industrial strain for the large scale production of the isoflavonoid genistein, as well as for the production of β-and γ- rhodomycinone to be used for the construction of new derivatives with more potent cytotoxic activities of the anthracycline family. This is the first report about the production of the isoflavonoid genistein by S. griseus KJ623766.