Abstract
Ursolic acid, an important bioactive compound, was isolated from ethanol extract of aerial parts of Sambucus australis. In order to develop bioactive ursolic acid derivatives, two semi-synthetic compounds were obtained through modification at C-3. The antibacterial activity of the ursolic acid and its derivatives was investigated. The microdilution method was used for determination of the minimal inhibitory concentration (MIC), against twelve bacterial strains. The influence of ursolic acid and its derivatives on the susceptibility of some bacterial pathogens to the aminoglycosides antibiotics neomycin, amikacin, kanamycin and gentamicin was evaluated. The most representative synergistic effect was observed by 3β-formyloxy-urs-12-en-28-oic acid at the concentration of 64 μg/mL in combination with kanamycin against Escherichia coli (27), a multidrug-resistant clinical isolate from sputum, with reduction of MIC value from 128 μg/mL to 8 μg/mL. Ursolic acid and its derivatives were examined for their radical scavenger activity using the DPPH assay, and showed significant activity.
Highlights
Ursolic acid (1), an ursane-type pentacyclic triterpene, is a constituent of certain medicinal herbs and is found in fruits [1]
In order to develop bioactive ursolic acid derivatives, two semi-synthetic compounds were obtained through modification at C-3
The antibacterial activity of ursolic acid (1) against several bacterial strains has been reported in the literature [8,10,11,12], in our case compound 1 showed activity against six bacterial strains, and the best result was found against S. aureus (ATCC 6538), with a minimal inhibitory concentration (MIC) value of 32 μg/mL
Summary
Ursolic acid (1), an ursane-type pentacyclic triterpene, is a constituent of certain medicinal herbs and is found in fruits [1]. This triterpenoid is the major secondary metabolite isolated from the ethanol extract of aerial parts of Sambucus australis Cham. The antibacterial properties of pentacyclic triterpenes and their derivatives have been extensively studied [10,11,12,13], and the activity of these compounds resides in their potential to enhance bacterial susceptibility to other compounds, including antibiotics [14]. The influence of the compounds 1, 1a and 1b on the susceptibility of several Gram-positive and Gram-negative bacteria towards the aminoglycoside antibiotics neomycin, amikacin, kanamycin and gentamicin was evaluated
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