Highly oxygenated dihydrostilbenoids and flavones from the aerial part of Glycyrrhiza uralensis and their antimicrobial activities

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Abstract Background Multidrug-resistant bacteria (MDRB) represent a significant global challenge due to their high mortality rates, substantial economic burden, and rapid spread. Traditional triple or quadruple therapies have demonstrated limited efficacy as a result of increasing drug resistance. Thus, it is urgent to develop novel anti-MDRB drugs with high efficiency and low toxicity. Objectives To isolate and identify the dihydrostilbenoids and flavones from the aerial part of Glycyrrhiza uralensis (Fabaceae) and their antimicrobial activities were screened. Materials and methods The aerial part of G. uralensis was extracted with 75% aqueous EtOH. The crude extract was repeatedly isolated by macroporous resin, silica gel, Sephadex LH-20, C18-MPLC, and MCI-MPLC, which were then purified by semipreparative RP-HPLC to obtain monomer compounds. The structures of the isolates were assigned by a combination of optical rotations, UV spectra, nuclear magnetic resonance, and high-resolution electrospray ionization mass spectrometry, and the absolute configurations of compounds 2, 3, and 7 were further confirmed by electronic circular dichroism calculations. Subsequently, we investigated their antimicrobial activities by the broth microdilution method. Results Seventeen previously undescribed phenolic compounds (1–17) and 26 known analogs (18–43), including dihydrostilbenoids, flavones, and dihydroflavones, were identified from the aerial part of G. uralensis. In vitro, antimicrobial bioassays demonstrated that compound 31 displayed the strongest inhibitory effect against 4 drug-resistant Helicobacter pylori strains (MIC = 2–4 μg/mL), comparable to metronidazole (MIC = 1–32 μg/mL). Additionally, compounds 10, 13, and 15 demonstrated bactericidal activity against Staphylococcus aureus (MIC = 4 μg/mL), while compounds 15 and 22 exhibited inactivation effects against Mycobacterium smegmatis, Enterococcus faecium, and E. faecalis (MIC = 4–8 μg/mL). Conclusions These monomeric compounds with antimicrobial activities were isolated from the aerial parts of G. uralensis, providing valuable insights into the potential anti-MDRB properties of its nonmedicinal parts.