Academic Editor: Jen-Tsung Chen
The search for new antimicrobials is essential to address
the worldwide issue of antibiotic resistance. The present work aimed at assessing
the antimicrobial activity of Aesculus hippocastanum L. (horse chestnut)
bark against bacteria involved in urinary tract infections (UTIs).
Bioactive compounds were extracted from A.
hippocastanum bark using water and ethanol as solvents. The extracts were tested
against 10 clinical uropathogenic strains including five Gram-positive and five
Gram-negative bacteria. Staphylococcus aureus ATCC 6538 and
Escherichia coli ATCC 25922 were used as reference bacteria. The susceptibility
to antibiotics was assessed using the Kirby Bauer disc diffusion method and the
antibacterial activity of the extracts was evaluated using the well diffusion
method. The Minimum inhibitory concentration (MIC) and the minimum bactericidal
concentrations (MBC) were asseded by the microdilution method.
A. hippocastanum bark possessed a dry matter content of 65.73%. The
aqueous extract (AE) and ethanolic extract (EE) showed a volume yield of 77.77%
and 74.07% (v/v), and a mass yields of 13.4% and 24.3% (w/w) respectively. All
the bacteria were susceptible to amoxiclav, imipenem and ceftriaxone but the
clinical strains were resistant to at least one antibiotic. Kocuria
rizophilia 1542 and Corynebacterium spp 1638 were the most resistant
bacteria both with multidrug resistance index of 0.45. Except AE on
Proteus Mirabilis 1543 and Enterococcus faecalis 5960 (0 mm),
both AE and EE were active against all the microorganisms tested with inhibition
diameters (mm) which ranged from 5.5–10.0 for AE and 8.0–14.5 for EE. The MICs
of EEs varied from 1–4 mg/mL while those of AEs varied from 4–16 mg/mL. The
ethanolic extracts (EE) were overall more active than the aqueous
ones. The A. hippocastanum bark extracts had
overall weak antibacterial activity (MIC