Biocidal effects of stem bark extract of Chrysophyllum albidium G. Don on vancomycin-resistant Staphylococcus aureus.

BACKGROUND: Staphylococcus aureus causes variety of infections in humans and animals worldwide and predominates in surgical wound infections. This study assessed the antimicrobial potential of the stem bark extract of Chrysophyllum albidum against an array of vancomycin resistant Staphylococcus aureus (VRSA) isolated from clinical samples. METHODS: The methanolic crude extract of the plant was preliminary screened for the presence of phytochemicals; after then, the extract was partitioned into n-hexane, chloroform, ethyl acetate and butanol fractions. A range of concentrations of the plant extract fractions was prepared to assess its antimicrobial potency; the minimum inhibitory concentrations (MICs); the minimum bactericidal concentrations (MBCs); the rate of killing; the potassium ion leakage potential and nucleotides leakage ability against the VRSAs. RESULTS: The phytochemical screening revealed the presence of tannins, alkaloids, flavonoids, saponins, steroids, reducing sugars and terpenoids as major phytoconstituents resident in the crude plant extract. The two active fractions (n-hexane and butanol) at a concentration of 10 mg/ml exhibited antibacterial activities with the MIC and MBC values for the fractions ranged between 0.63-10 mg/ml and 1.25-10 mg/ml respectively. The time kill assay revealed that the antibacterial action of the two fractions are time and concentration dependent; the n-hexane and butanol fractions achieved 100 % kill on the test isolates at a concentration of 3 × MIC and 2 × MIC respectively after 120 min of reaction time. Varying amount of potassium ions as well as nucleotides were leaked from the test cells by n-hexane and butanol fractions. CONCLUSIONS: This study has established the possibility of developing antimicrobial agents of natural origin to manage possible infection from vancomycin resistant Staphylococcus aureus that are now developing multi-resistance against many antibiotics.

Probable mechanisms of biocidal action of Cocos nucifera Husk extract and fractions on bacteria isolates.

BACKGROUND: The incidence of resistance to the existing antibiotics by microorganisms demand increased effort in the development of new antibiotics for the treatment of microbial infections and diseases. Infections due to multidrug resistant pathogens are difficult to manage due to relatively limited choices of antimicrobial agents. This study investigated antimicrobial activities of the husk extract of Cocos nucifera on some bacteria that are associated with human diseases. METHODS: Powdered husk of Cocos nucifera was cold extracted using mixture of methanol and distilled water in ration 3:2 (v/v). Extract was partitioned into n-hexane. Chloroform, ethylacetate and n-butanol fractions and thereafter, the minimum inhibitory concentrations (MICs) of the extract and those of the fractions were determined. The ethylacetate fraction was found to be more active and was partially purified by a combination of thin-layer and column chromatography. Finally, the rate of killing, leakages of proteins, potassium ions and nucleotides from the tests bacterial cells were determined. RESULTS: The minimum Inhibitory concentrations (MICs) of the extract ranged between 0.39 and 12.50 mg/ml and those of the fractions ranged between 0.16 and 5.00 mg/ml. The time-kill assay revealed a minimum of 27.8% killed at 1 × MIC after 15 min contact time with the fractions and a minimum of 95% killed after 120 min. Varying amount of proteins, potassium ions as well as nucleotides were leaked from selected bacterial isolates by the four active fractions. The amount of proteins leaked from the cells after 15 min contact time ranged between 3.56 and 19.08 µg/ml at 1 × MIC and between 10.97 and 19.54 µg/ml at 2 × MIC. The amount of potassium ions leaked from the cells after 15 min contact time ranged between 0.182 and 0.379 mg/ml at 1 × MIC and between 0.227 and 0.561 mg/ml at 2 × MIC. The nucleotides leaked from the cells after 15 min contact time ranged between 0.609 and 2.446 µg/ml at 1 × MIC and between 0.897 and 2.841 µg/ml at 2 × MIC. CONCLUSIONS: This study established the possibility of developing antimicrobial agents of natural origin to combat resistance to antimicrobial compounds by some pathogens currently being experienced in agricultural and health care environments.

Evaluation of Antibacterial and Antifungal Properties of Alchornea laxiflora (Benth.) Pax. & Hoffman.

Alchornea laxiflora leaf extract was tested against a range of microorganisms using standard microbiological methods for antimicrobial activities. The extract inhibited the growth of all the bacterial and 15 fungal isolates tested. The zones of inhibition exhibited against the test bacteria ranged between 12 mm and 24 mm and between 11 mm and 24 mm for the extract and the antibiotic streptomycin, respectively. The zones of inhibition observed against the fungal isolates by the extract ranged between 12 mm and 23 mm. The minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) exhibited by the extract against test bacteria ranged between 0.78 mg/mL-25 mg/mL and 1.56 mg/mL-25 mg/mL, respectively, while the MICs and minimum fungicidal concentrations (MFCs) values for the test fungi ranged between 8.75 mg/mL-35.00 mg/mL and 8.75 mg/mL-35.00 mg/L, respectively. The preliminary phytochemical screening of the extract revealed the presence of alkaloids, tannins, flavonoids, saponins, and reducing sugars as major phytoconstituents in the extract. A. laxiflora leaf extract is a potent source of antibacterial and antifungal compounds; further studies on the extract are ongoing in our laboratories to elucidate the probable mechanism(s) of action on bacteria and fungi found to be susceptible to the extract.

Stem bark extract and fraction of Persea americana (Mill.) exhibits bactericidal activities against strains of bacillus cereus associated with food poisoning.

The study investigates the in vitro antibacterial potentials of stem bark extracts of Persea americana on strains of Bacillus cereus implicated in food poisoning. The crude stem bark extracts and butanolic fraction at a concentration of 25 mg/mL and 10 mg/mL, respectively, exhibited antibacterial activities against test isolates. The zones of inhibition exhibited by the crude extract and the fraction ranged between 10 mm and 26 mm, while the minimum inhibitory concentration values ranged between 0.78 and 5.00 mg/mL. The minimum bactericidal concentrations ranged between 3.12 mg/mL-12.5 mg/mL and 1.25-10 mg/mL for the extract and the fraction, respectively. The butanolic fraction killed 91.49% of the test isolates at a concentration of 2× MIC after 60 min of contact time, while a 100% killing was achieved after the test bacterial cells were exposed to the butanolic fraction at a concentration of 3× MIC after 90 min contact time. Intracellular protein and potassium ion leaked out of the test bacterial cells when exposed to certain concentrations of the fraction; this is an indication of bacterial cell wall disruptions by the extract's butanolic fraction and, thus, caused a biocidal effect on the cells, as evident in the killing rate test results.

Preliminary phytochemical screening and antibacterial properties of crude stem bark extracts and fractions of Parkia biglobosa (Jacq.).

A methanolic crude extract of Parkia biglobosa was prepared and later partitioned in succession with different solvents of increasing polarity ranging from n-hexane, chloroform and ethyl acetate to butanol. Phytochemical screening of the extract revealed the presence of alkaloids, tannins, saponins, flavonoids, steroids, glycoside and sugars. The inhibition zones exhibited by the extract against the tested bacteria ranged between 14 ± 0.00 mm (against Escherichia coli) and 28 ± 0.71 mm (against Pseudomonas aeruginosa). The MIC of the methanolic extract of P. biglobosa against isolates ranged between 0.63 mg/mL and 5 mg/mL, while the MIC values exhibited by the n-hexane and aqueous fractions ranged between 0.63 mg/mL and 10 mg/mL. Overall the extract and fractions of P. biglobosa used in this work were found to possess antimicrobial properties which compared favourably with those of streptomycin. These observations make this plant a potential source of bioactive compounds that can be used in management of bacterial infections. The use of this plant as herbal medicaments in African countries and the reports on the toxicity of the plant further show that the plant is non-toxic to humans.

Antibiotic producing potentials of three freshwater actinomycetes isolated from the Eastern Cape Province of South Africa.

Crude extracts of three actinomycetes species belonging to Saccharopolyspora (TR 046 and TR 039) and Actinosynnema (TR 024) genera were screened for antibacterial activities against a panel of several bacterial strains. The extracts showed antibacterial activities against both gram-negative and gram-positive test bacteria with inhibition zones ranging from 8 to 28 mm (TR 046); 8 to15 mm (TR 039); and 10 to 13 mm (TR 024). The minimum inhibitory concentrations ranged from 0.078 to 10 mg/mL (TR 046); 5 to >10 mg/mL (TR 039); and 1.25 to 5 mg/mL (TR 024). Time-kill studies revealed that crude extract of TR 046 showed strong bactericidal activity against Bacillus pumilus (ATCC14884), reducing the bacterial load by 10(4) cfu/mL and 10(2) cfu/mL at 4x MIC and 2x MIC, respectively, after 6 h of exposure. Similarly, against Proteus vulgaris (CSIR 0030), crude extract of TR 046 achieved a 0.9log(10) and 0.13log(10) cfu/mL reduction at 5 mg/mL (4x MIC) and 1.25 mg/mL (2x MIC) after 12 h of exposure. The extract was however weakly bactericidal against two environmental bacterial strains (Klebsiella pneumoniae and Staphylococcus epidermidis); and against Pseudomonas aeruginosa (ATCC 19582): the extract showed bacteriostatic activities at all concentrations tested. These freshwater actinomycetes appear to have immense potential as a source of new antibacterial compound(s).

Microwave assisted synthesis and antimicrobial activity of 2-quinoxalinone-3-hydrazone derivatives.

A simple and efficient method has been developed for the synthesis of various 2-quinoxalinone-3-hydrazone derivatives using microwave irradiation technique. The series of 2-quinoxalinone-3-hydrazone derivatives synthesized, were structurally confirmed by analytical and spectral data and evaluated for their antimicrobial activities. The results showed that this skeletal framework exhibited marked potency as antimicrobial agents. The most active antibacterial agent was 3-{2-[1-(6-chloro-2-oxo-2H-chromen-3-yl)ethylidene]hydrazinyl}quinoxalin-2(1H)-one, 7 while 3-[2-(propan-2-ylidene)hydrazinyl]quinoxalin-2(1H)-one, 2 appeared to be the most active antifungal agent.

Studies on the biocidal and cell membrane disruption potentials of stem bark extracts of Afzelia africana (Smith).

We had recently reported antibacterial activity in the crude extract of the stem bark of Afzelia africana (Akinpelu et al., 2008). In this study, we assessed the biocidal and cell membrane disruption potentials of fractions obtained from the crude extract of the plant. The aqueous (AQ) and butanol (BL) fractions exhibited appreciable antibacterial activities against the test bacteria. The minimum inhibitory concentrations of the AQ and BL fractions ranged between 0.313 and 2.5 mg/ml, while their minimum bactericidal concentrations varied between 0.625 and 5.0 mg/ml. Also, the AQ fraction killed about 95.8% of E. coli cells within 105 min at a concentration of 5 mg/ml, while about 99.1% of Bacillus pumilus cells were killed by this fraction at the same concentration and exposure time. A similar trend was observed for the BL fraction. At a concentration of 5 mg/ml, the butanol fraction leaked 9.8 microg/ml of proteins from E. coli cells within 3 h, while the aqueous fraction leaked 6.5 microg/ml of proteins from the same organisms at the same concentration and exposure time. We propose that the stem bark of Afzelia africana is a potential source of bioactive compounds of importance to the pharmaceutical industry.

Studies on the biocidal and cell membrane disruption potentials of stem bark extracts of Afzelia africana (Smith)

We had recently reported antibacterial activity in the crude extract of the stem bark of Afzelia africana (Akinpelu et al., 2008). In this study, we assessed the biocidal and cell membrane disruption potentials of fractions obtained from the crude extract of the plant. The aqueous (AQ) and butanol (BL) fractions exhibited appreciable antibacterial activities against the test bacteria. The minimum inhibitory concentrations of the AQ and BL fractions ranged between 0.313 and 2.5 mg/ml, while their minimum bactericidal concentrations varied between 0.625 and 5.0 mg/ml. Also, the AQ fraction killed about 95.8 percent of E. coli cells within 105 min at a concentration of 5 mg/ml, while about 99.1 percent of Bacillus pumilus cells were killed by this fraction at the same concentration and exposure time. A similar trend was observed for the BL fraction. At a concentration of 5 mg/ml, the butanol fraction leaked 9.8 μg/ml of proteins from E. coli cells within 3 h, while the aqueous fraction leaked 6.5 μg/ml of proteins from the same organisms at the same concentration and exposure time. We propose that the stem bark of Afzelia africana is a potential source of bioactive compounds of importance to the pharmaceutical industry.