Bark extract of Cassia sieberiana DC. (Caesalpiniaceae) displayed good antibacterial activity against MDR gram-negative phenotypes in the presence of phenylalanine-arginine β-naphthylamide

Abstract

Background Multidrug-resistant (MDR) bacteria remain a major cause of morbidity and mortality globally. The present study was designed to investigate the in vitro antibacterial activities of crude methanol extract and constituents isolated by Column Chromatography (CC) from Cassia sieberiana bark (CSB) against ten MDR Gram-negative bacteria, as well as the mechanisms of action of the most active sample. Methods The antibacterial activity of the tested samples (extract, the fractions and their compounds isolated by CC and the structures obtained by exploiting 1H and 13C Nuclear magnetic resonance (NMR) spectra) in the presence and absence of an efflux pumps inhibitor, phenylalanine-arginine β-naphthylamide (PAβN), was evaluated using the micro-dilution method. The effects of the most active sample were evaluated on the cell growth kinetic and on the bacterial H+-ATPase proton pumps. Results Phytochemical composition of the crude extract showed a rather selective distribution of secondary metabolites (presence of polyphenols, tannins, steroids, triterpenes, flavonoids, alkaloids, saponins and absence of anthocyanins, anthraquinones). The tested samples displayed different antibacterial activities with minimal inhibitory concentrations (MICs) ranging from 64 to 512 μg/mL. Crude extract (CS) and fraction CSc showed the highest inhibitory spectra, both inhibiting all of the studied bacteria except Enterobacter aerogenes EA27 strain. Fraction CSc exerted bactericidal effects on most bacteria meanwhile, crude extract (CS) and sub-fraction CSc2 exerted bacteriostatic effects. Compounds 1 (spectaline) and 2 (iso-6-cassine) inhibited the growth of 70% (Escherichia coli ATCC8739 and AG102, Klebsiella pneumoniae ATCC11296, Enterobacter aerogenes ATCC13048 and EA27, Providencia stuartii ATCC29916, Pseudomonas aeruginosa PA01) and 60% (Escherichia coli ATCC8739, Klebsiella pneumoniae ATCC11296 and KP55, Providencia stuartii ATCC29916, Pseudomonas aeruginosa PA01 and PA124) of bacteria respectively with MICs ranging from 128 to 512 μg/mL. In the presence of PAβN, the activities of crude extract CS, fraction CAc and sub-fraction CSc2 strongly increased on most bacteria strains as their MICs significantly decreased. Sub-fraction CSc2 inhibited the H+-ATPase proton pumps and altered growth kinetic of Escherichia coli ATCC8739. Conclusion The overall results justify the traditional use of C. sieberiana for the treatment of bacterial infections.

In vivo assessment of antibacterial activity of Cassia sieberiana stem bark extracts on enterohaemorrhagic Escherichia coli infection in Wister rats

“…However, in all the infected rats, treatment with either aqueous or ethanolic extract reduced EHEC counts to zero level after 7 days of extract administration. Our findings agree with reports of previous studies on similar plant extracts (27,33).…”

“…Apart from the documented antimicrobial activity of alkaloids, a major phytochemical constituent of C. sieberiana stem bark (27), against bacterial infections, flavonoids, tannins and saponins present in the stem are also known to possess antimicrobial potential by either altering the bacterial cell membrane or inhibiting the synthesis of nuclei acid and proteins (33). Cassia sieberiana has been shown to possess both bacteriostatic and bactericidal effects against E. coli, Staphylococcus aureus, Pseudomonas spp.…”

“…They have marked physiological effects on animals and show considerable pharmacological activity (8). Alkaloids are stimulants that act by prolonging actions of several hormones which require phosphodiesterase (7,8), though are poisonous to cattle (9). Tannins are useful in medicine because of their astringent properties.…”

“…Tannins are useful in medicine because of their astringent properties. Tannins and alkaloids are also known to have anti-herbivore defense functions in plants (5,9). Thus, the presence of tannins and alkaloids in this medicinal plant could be serving as a deterrent to grazers (8).…”

Antibiotic resistance of Aeromonas spp. isolated from diseased walking catfish (Clarias sp.)

“…Bacteria that grew in wells with the highest concentration of antibiotics (10 µg/mL) were considered resistant to these antibiotics. Ambadiang et al (2020) revealed that MIC ≤ 10 µg/mL indicates strong activity. Thus, no inhibitory test with antibiotic concentrations above 10 µg/mL was conducted because it is no longer effective.…”