Determinants of Antibacterial Activity in Humulus lupulus Hop Extracts: Phytochemical Profiling of Prenylated Acylphloroglucinols and Efficacy Against Methicillin-Resistant Staphylococcus aureus and Multidrug-Resistant Uropathogenic Escherichia coli
- 1Department of Fermentation and Cereals Technology, Faculty of Biotechnology and Food Science, Wroclaw University of Environmental and Life Sciences, Chełmońskiego 37 Street, 51-630 Wroclaw, Poland
- 2Department of Biology and Medical Parasitology, Faculty of Medicine, Wroclaw Medical University, Mikulicza-Radeckiego 9, 50-345 Wroclaw, Poland
- 3Department of Pharmacognosy and Herbal Medicines, Wroclaw Medical University, Borowska 211a, 50-556 Wroclaw, Poland
Abstract
Optimizing hop (Humulus lupulus L.) extraction protocols for maximum antibacterial efficacy remains an open methodological challenge in developing plant-based natural antimicrobials. We compared five extraction protocols—hot ethanol, cold ethanol, espresso/steam, hot water, and cold water—applied to four hop varieties (Citra, Lubelski, Magnat and Marynka), with a commercial supercritical CO2 extract as a reference preparation. We characterized extracts by HPLC (α-acids, β-acids, iso-α-acids) and GC-MS (volatile profile of cold ethanol extracts) and determined antibacterial activity as minimum inhibitory concentration (MIC) against reference and clinically relevant multidrug-resistant (MDR) strains of Escherichia coli and Staphylococcus aureus. Friedman tests confirmed a statistically significant effect of extraction method on MIC values (p ≤ 0.004 for E. coli ATCC 25922, S. aureus ATCC 29213, and clinical MRSA). Ethanol-based protocols consistently produced the highest hop acid concentrations and the lowest MICs against S. aureus ATCC 29213 (0.125–0.250 mg/mL) and against clinical MRSA (as low as 0.016 mg/mL), compared with 1.0–15.0 mg/mL for aqueous and steam-based extracts. Clinical MRSA demonstrated increased susceptibility to selected ethanol extracts and to the CO2 reference. MDR uropathogenic E. coli (UPEC) maintained high-level resistance (MIC 15 mg/mL) to all preparations except the CO2 reference (MIC 6 mg/mL). Spearman correlation identified α-acid content as the dominant predictor of antibacterial activity (ρ = −0.927, p < 0.001 for S. aureus ATCC 29213). These results suggest ethanol-based and supercritical CO2 extraction as optimal protocols for producing hop extracts with antibacterial properties targeting Gram-positive pathogens, including MRSA, and provide a rationale for their use as natural antimicrobials.
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BibTeX
@article{leszczynski2026determinants,
title = {{Determinants of Antibacterial Activity in Humulus lupulus Hop Extracts: Phytochemical Profiling of Prenylated Acylphloroglucinols and Efficacy Against Methicillin-Resistant Staphylococcus aureus and Multidrug-Resistant Uropathogenic Escherichia coli}},
author = {Przemysław Leszczyński and Dorota Wojnicz and Dorota Tichaczek-Goska and Michał Gleńsk and Alan Gasiński and Joanna Kawa-Rygielska},
journal = {International Journal of Molecular Sciences},
year = {2026},
month = sep,
doi = {10.3390/ijms27188364},
url = {https://www.mdpi.com/1422-0067/27/18/8364},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Determinants of Antibacterial Activity in Humulus lupulus Hop Extracts: Phytochemical Profiling of Prenylated Acylphloroglucinols and Efficacy Against Methicillin-Resistant Staphylococcus aureus and Multidrug-Resistant Uropathogenic Escherichia coli
AU - Przemysław Leszczyński
AU - Dorota Wojnicz
AU - Dorota Tichaczek-Goska
AU - Michał Gleńsk
AU - Alan Gasiński
AU - Joanna Kawa-Rygielska
PY - 2026
DA - 2026/09/19
JO - International Journal of Molecular Sciences
DO - 10.3390/ijms27188364
UR - https://www.mdpi.com/1422-0067/27/18/8364
AB - Optimizing hop (Humulus lupulus L.) extraction protocols for maximum antibacterial efficacy remains an open methodological challenge in developing plant-based natural antimicrobials. We compared five extraction protocols—hot ethanol, cold ethanol, espresso/steam, hot water, and cold water—applied to four hop varieties (Citra, Lubelski, Magnat and Marynka), with a commercial supercritical CO2 extract as a reference preparation. We characterized extracts by HPLC (α-acids, β-acids, iso-α-acids) and GC-MS (volatile profile of cold ethanol extracts) and determined antibacterial activity as minimum inhibitory concentration (MIC) against reference and clinically relevant multidrug-resistant (MDR) strains of Escherichia coli and Staphylococcus aureus. Friedman tests confirmed a statistically significant effect of extraction method on MIC values (p ≤ 0.004 for E. coli ATCC 25922, S. aureus ATCC 29213, and clinical MRSA). Ethanol-based protocols consistently produced the highest hop acid concentrations and the lowest MICs against S. aureus ATCC 29213 (0.125–0.250 mg/mL) and against clinical MRSA (as low as 0.016 mg/mL), compared with 1.0–15.0 mg/mL for aqueous and steam-based extracts. Clinical MRSA demonstrated increased susceptibility to selected ethanol extracts and to the CO2 reference. MDR uropathogenic E. coli (UPEC) maintained high-level resistance (MIC 15 mg/mL) to all preparations except the CO2 reference (MIC 6 mg/mL). Spearman correlation identified α-acid content as the dominant predictor of antibacterial activity (ρ = −0.927, p < 0.001 for S. aureus ATCC 29213). These results suggest ethanol-based and supercritical CO2 extraction as optimal protocols for producing hop extracts with antibacterial properties targeting Gram-positive pathogens, including MRSA, and provide a rationale for their use as natural antimicrobials.
SN - 1422-0067
ER -