In this work we report the isolation, identification and antibacterial activity of two anthraquinones, 2-hydroxy-1-methoxyanthraquinone (1) and 2,5-dihydroxy-1-methoxy-6-methoxymethylanthraquinone (2), from the stem bark of Morinda lucida. These two natural products were selectively converted into two new glycosylated derivatives, 2-hydroxy-1-methoxyanthraquinone-4′-O-methyl-2-O-β-D-glucopyranoside (3) and 2,5-dihydroxy-1-methoxy-6-methoxymethylanthraquinone-4′-O-methyl-2-O-β-D-glucopyranoside (4) by the filamentous fungus Beauveria bassiana ATCC 7159. Structure elucidation was accomplished based on the 1D and 2D NMR, IR and mass spectra. The glycosylated compounds 3 and 4 showed higher in vitro antibacterial activity against Salmonella enterica subsp. enterica sérovars Typhimurim (MIC of 8 μg/mL each) than the corresponding aglycons 1 and 2 (MIC of 16 μg/mL and 32 μg/mL, respectively). These results indicated that microbial glycosylation is an effective approach to modify natural products for enhanced biological activities.
antibacterial activity, Beauveria bassiana, microbial biotransformation, 4'-O-methylglycosylation, anthraquinones, Morinda lucida
Publication DOI: 10.1016/j.phytol.2020.04.011Journal NLM ID: 101513432Publisher: Amsterdam: Elsevier
Correspondence: Mbah JA
; Zhan J
Institutions: Department of Biological Engineering, Utah State University, Logan, USA, Department of Chemistry, University of Buea, Buea, Cameroon, Department of Biochemistry, University of Dschang, Dschang, Cameroon
Methods: 13C NMR, 1H NMR, NMR-2D, IR, TLC, ESI-MS, HPLC, extraction, CC, cell growth, melting point determination, HR-ESI-MS, antibacterial assay, evaporation, centrifugation
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