Antistaphylococcal and biofilm inhibitory activities of acetyl-11-keto-β-boswellic acid from Boswellia serrata

Abstract

BackgroundBoswellic acids are pentacyclic triterpenes, which are produced in plants belonging to the genus Boswellia. Boswellic acids appear in the resin exudates of the plant and it makes up 25-35% of the resin. β-boswellic acid, 11-keto-β-boswellic acid and acetyl-11-keto-β-boswellic acid have been implicated in apoptosis of cancer cells, particularly that of brain tumors and cells affected by leukemia or colon cancer. These molecules are also associated with potent antimicrobial activities. The present study describes the antimicrobial activities of boswellic acid molecules against 112 pathogenic bacterial isolates including ATCC strains. Acetyl-11-keto-β-boswellic acid (AKBA), which exhibited the most potent antibacterial activity, was further evaluated in time kill studies, postantibiotic effect (PAE) and biofilm susceptibility assay. The mechanism of action of AKBA was investigated by propidium iodide uptake, leakage of 260 and 280 nm absorbing material assays.ResultsAKBA was found to be the most active compound showing an MIC range of 2-8 μg/ml against the entire gram positive bacterial pathogens tested. It exhibited concentration dependent killing of Staphylococcus aureus ATCC 29213 up to 8 × MIC and also demonstrated postantibiotic effect (PAE) of 4.8 h at 2 × MIC. Furthermore, AKBA inhibited the formation of biofilms generated by S. aureus and Staphylococcus epidermidis and also reduced the preformed biofilms by these bacteria. Increased uptake of propidium iodide and leakage of 260 and 280 nm absorbing material by AKBA treated cells of S aureus indicating that the antibacterial mode of action of AKBA probably occurred via disruption of microbial membrane structure.ConclusionsThis study supported the potential use of AKBA in treating S. aureus infections. AKBA can be further exploited to evolve potential lead compounds in the discovery of new anti-Gram-positive and anti-biofilm agents.

Antibacterial effect of Thymus sp. and Boswellia sp. extracts on Streptococcus pneumoniae and Klebsiella pneumoniae isolates

“…The resistance of some of the Gram-negative bacteria could be due to the more hydrophilic outer membrane containing lipopolysaccharide (LPS), and the outer membrane acting as a penetration barrier for macromolecules and hydrophobic compounds (Nikaido, 1996). Raja et al (2011) reported that the lack of antibacterial activity of active compounds of Boswellia sp. against Gramnegative bacteria might be attributed due to the presence of lipophilic outer membrane in Gram-negative, which composed primarily of lipopolysaccharide molecules and forms hydrophilic permeability barrier providing protection against the effects of highly hydrophobic compounds.…”

Antibacterial and antibiofilm activity of Ammi majus seed against Gram-positive bacteria

“…Staphylococci have the ability to form biofilms on an implanted medical device or damaged tissues and these biofilms are difficult to eradicate. 21 The highest antibiofilm activity documented for ethanol 80% extract 95.2% and ethyl acetate extract 93.9% against Staphylococcus aureus, while the lowest documented for ethanol 80 % extract 55.4 % and ethyl acetate extract 59.3% against Streptococcus mitis (Table 3 and 4). However, none of the extracts was able to inhibit biofilm formation completely this may be due to solubility and diffusion of phytochemical constituents in agar media.…”

“…21 Twofold serial dilutions of plant extract were made in sterile 96 flat wells microtiter plates containing 100 μl of Nutrient broth per well. The tested concentration ranged from (0.4883-62.5) mg/ml for ethanol 80 % and ethyl acetate fraction.…”

First report on rapid screening of nanomaterial-based antimicrobial agents against β-lactamase resistance using pGLO plasmid transformed Escherichia coli HB 101 K-12

“…This is due to the presence of lipophilic outer membrane in Gram-negative bacteria, which acts as a hydrophilic permeability barrier for the entry of hydrophobic compounds such as AKBA (Raja et al 2011;Hancock 1997;Helander et al 1998). Similar observations were made in studies dealing with antibacterial activity of other hydrophobic compounds against Gram-negative bacteria (Trombetta et al 2005;Gallucci et al 2009).…”