Azacoccones F-H, new flavipin-derived alkaloids from an endophytic fungus Epicoccum nigrum MK214079

Harwoko, Harwoko and Lee, Jungho and Hartmann, Rudolf and Mándi, Attila and Kurtán, Tibor and Müller, Werner E. G. and Feldbrügge, Michael and Kalscheuer, Rainer and Ancheeva, Elena and Daletos, Georgios and Frank, Marian and Liu, Zhen and Proksch, Peter (2020) Azacoccones F-H, new flavipin-derived alkaloids from an endophytic fungus Epicoccum nigrum MK214079. FITOTERAPIA, 146. p. 104698. ISSN 0367-326X

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Abstract

Three new flavipin-derived alkaloids, azacoccones F-H (1–3), along with six known compounds (4–9) were isolated from the endophytic fungus Epicoccum nigrum MK214079 associated with leaves of Salix sp. The structures of the new compounds were established by analysis of their 1D/2D nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectroscopy (HRESIMS) data. The absolute configuration of azacoccones F-H (1–3) was determined by comparison of experimental electronic circular dichroism (ECD) data with reported ones and biogenetic considerations. Epicocconigrone A (4), epipyrone A (5), and epicoccolide B (6) exhibited moderate antibacterial activity against Staphylococcus aureus ATCC 29213 with minimal inhibitory concentration (MIC) values ranging from 25 to 50 μM. Furthermore, epipyrone A (5) and epicoccamide A (7) displayed mild antifungal activity against Ustilago maydis AB33 with MIC values of 1.6 and 1.8 mM, respectively. Epicorazine A (8) showed pronounced cytotoxicity against the L5178Y mouse lymphoma cell line with an IC50 value of 1.3 μM.

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