Bolanle A. Adeniyi

Antimicrobial activity of the essential oils of five Eucalyptus species growing in Nigeria

At 5 mg/ml concentration, the volatile oils from the leaves of five Eucalyptus spp growing in Nigeria exhibited considerable antibacterial activity against Gram-positive and Gram-negative microorganisms and antifungal activity against C. albicans.

Evaluation of the functional potential of Weissella and Lactobacillus isolates obtained from Nigerian traditional fermented foods and cow's intestine

The characterisation of 24 lactic acid bacteria (LAB) isolates from Nigerian traditional fermented dairy foods, including some cows intestine isolates, was conducted in order to select isolates for potential use as probiotics. LAB isolates were identified by partial sequencing the 16S rRNA gene as belonging to the species Lactobacillus paracasei, Lactobacillus brevis and mainly Weissella confusa. At the end of a characterisation process, 2 L. paracasei and 2 W. confusa isolates were selected, and their resistance to a simulated gastrointestinal digestion and their ability to adhere to eukaryotic cell lines were assessed. The survival to the simulated gastrointestinal passage was higher when bacterial suspensions were made in skimmed milk (2.0±0.8 log units reduction) or at the simulated gastric juice pH 3 (2.7±0.9 log units reduction) than at pH 2.0 (5.5±0.7 log units reduction). Adhesion of LAB to both intestinal and vaginal epithelial models was comparable or higher than that of the reference Lactobacillus rhamnosus GG. However, some of the isolates increased the adhesion of the pathogen Escherichia coli LMG2092 to HT-29 and HeLa monolayers. Overall, isolates L. paracasei UI14 and W. confusa UI7 are good candidates for further studying potential benefits that support their use as probiotics. This is one of the few articles reporting the characterisation and the probiotic potential of Weissella, although more studies are needed in order to establish their safety for potential probiotic applications.

Antimicrobial activity of the essential oil of Hyptis suaveolens leaves

The essential oil of Hyptis suaveolens leaves showed antibacterial activity at 5 mg/ml concentration against two gram-positive and four gram-negative bacteria.

Antibacterial activity of diospyrin, isodiospyrin and bisisodiospyrin from the root of Diospyros piscatoria (Gurke) (Ebenaceae).

Two dimeric naphthoquinones, diospyrin and isodiospyrin, isolated from the root of Diospyros piscatoria (Gurke), a common ingredient in several folk medicines, have been shown to have a broad spectrum of antibacterial activity. The minimum inhibitory concentrations (MICs) of diospyrin against Streptococcus pyogenes ATCC 12344 and Streptococcus pneumoniae ATCC 33400 ranged from 1.56 to 50 µg/mL. While those against Salmonella choleraesuis serotype typhi (S. typhi), ATCC 6539 and Mycobacterium chelonae ATCC 19977 were between 25 and 100 µg/mL. Isodiospyrin was more active than its racemic isomer diospyrin. The MICs against Gram‐positive bacteria ranged from 0.78 to 50 µg/mL. While those against Pseudomonas aeruginosa ATCC 15443 and S. typhi ranged from 50 to 100 µg/mL. The MIC for M. chelonae was between 6.25 and 25 µg/mL. MICs were found to increase with the concentration of cells used for the inoculum. The MICs for Bacillus subtilis ATCC 6633 increased up to the highest concentration of cells tested. The same phenomenon was observed on M. chelonae, but with better effect in the latter. The kinetics of bacteria studies against both B. subtilis and M. chelonae increases with increasing concentration of isodiospyrin tested.

The antimicrobial activity of roots of Jatropha podagrica (Hook).

Hexane, chloroform and methanol extracts of the rootwood and rootbarks of Jatropha podagrica were studied for their antimicrobial activity against 18 organisms. All the extracts exhibited some broad spectrum antibacterial activity, at a concentration of 20 mg/mL. The hexane extracts were generally more active than the chloroform and methanol extracts. The hexane extract of the yellow rootbark was the most active of all the extracts and its activity was comparable to that of gentamycin but better with regard to the control of S. aureus and B. cereus. Three of the extracts, hexane extract of the yellow rootbark and hexane and methanol extracts of the rootwood showed moderate antifungal activity against the yeast fungus, Candida albicans. Copyright

Inhibition of uropathogens by lactic acid bacteria isolated from dairy foods and cow's intestine in western Nigeria

A total of 96 lactic acid bacteria (LAB) were isolated from African indigenous fermented products and cow’s intestines to study their inhibitory capability against multi-drug-resistant uropathogens. Escherichia coli accounted for approximately 45% of isolated uropathogens, followed by Staphylococcus spp. (20%). The Gram negative uropathogens were highly resistant to quinolones, co-trimoxazole, teicoplanin and some β-lactams, while the Staphylococcus spp. showed high resistance to aminoglycosides, β-lactams and macrolides. Twenty-four LAB isolates were selected based on their antimicrobial activity against two uropathogenic Staphylococcus aureus strains and bacteriocin production. LAB strains showing antimicrobial activity were grouped into smaller groups through amplified ribosomal DNA restriction analysis (ARDRA). Representative strains were identified as Weissella spp., Enterococcusfaecium, Lactococcus lactis and Lactobacillus brevis through sequencing of 16S rDNA. The Weissella spp. and L. brevis strains demonstrated remarkable inhibitory activity against seven strains of Gram negative uropathogens. Two strains of L. lactis produced a bacteriocin-like inhibitory substance active against Lactobacillus sakei. In this study, an unusual high rate of co-trimoxazole, quinolones and macrolides resistance among uropathogens from south west Nigeria was discovered. Based on their sensitivity to Weissella spp., there is a potential for using these LAB as a natural approach for the protection against the uropathogens assayed.

Anti-Helicobacter pylori activities of Eucalyptus grandis: Effects on susceptibility, urease activity and cell surface hydrophobicity

Helicobacter pylori is the primary etiologic agent of peptic ulcer, duodenal ulcer, chronic gastritis, gastric adenocarcinoma and related gastroduodenal disorders. Current triple therapy, including antibiotics and proton-pump inhibitors, has been successful; however, adverse events, non-patient compliance and consequent relapse of Helicobacter pylori infections are common. Crude methanol extracts of Eucalyptus grandis Hill ex. Maiden (Myrtaceae) stem bark were screened against a standard strain ATCC 43504 and ten clinical strains of H. pylori using the agar diffusion method on Mueller-Hinton agar supplemented with defibrinated horse blood and grown in a microaerophilic incubator. All the strains except UCH 97002 and UCH 98020 were inhibited by the extract to varying degrees. The minimum inhibitory concentration (MIC) against the susceptible strains tested ranged from 0.39 and 1.56 μg/mL. The urease activity of the three H. pylori strains tested decreased with increasing concentrations of the extract. The greatest inhibition of urease activity was observed in clinical strain UCH 97009. In addition, methanol extracts of the E. grandis enhanced cell aggregation of seven of the H. pylori strains leading to a decrease in the cell surface hydrophobicity. The salt aggregation test titer decreased from >3 to <1.5 for five of the strains and to <3 for two of the strains. Phytochemical screening of the plant revealed the presence of tannins, essential oils and saponins, while alkaloids were not detected. The anti-Helicobacter pylori activity observed in this study correlates well with the traditional use of this plant in Nigeria.

Antibacterial activities of lactic acid bacteria isolated from cow faeces against potential enteric pathogens

BACKGROUND The addition of sub therapeutic doses of antibiotics to cattle feed for growth promotion is a contributory factor to antibiotic resistance, thus an alternative to antibiotics is needed in animal feed additives. OBJECTIVE To determine the antimicrobial activity of cows intestinal Lactic acid bacteria (LAB) against enteric commensals. METHOD Escherichia coli, Klebsiella species (spp) and LAB were isolated from thirty different cow faecal samples and the LAB identified by partial sequencing of 16S rRNA. The antimicrobial activity of the LAB was determined against the test Escherichia coli and Klebsiella spp. RESULTS Five species of LAB were isolated from thirty cow faecal samples and identified as Enterococcus hirae (8), Enterococcus durans (6), Enterococcus faecium (1), Enterococcus faecalis (1) and Weissella confusa (1). Viable cells and cell free supernatant (CFS) of the LAB were able to inhibit the growth of the test organisms with the largest zone of inhibition by the viable cells being 26mm against Escherichia coli CB6 produced by Enterococcus hirae CO6A while Weissella confusa CO29M and Enterococcus hirae CO2A produced the largest zones of inhibition (26mm) against Klebsiella CB2. CONCLUSION This study shows that LAB from cow faeces possess considerable antimicrobial activity against resistant Escherichia coli from the same environment.

Combination Studies of Eucalyptus torelliana F. Muell. Leaf Extracts and Clarithromycin on Helicobacter pylori

Helicobacter pylori is a Gram‐negative bacillus that is associated with the development of gastritis and peptic ulcer disease (PUD). In Nigeria, leaf extracts of Eucalyptus torelliana F. Muell. are used in traditional medicine to treat PUD and other gastrointestinal ailments. The additive and synergistic effects of E. torelliana leaf extracts, in combination with clarithromycin, were investigated using two types of H. pylori strains (ATCC 43629, ATCC 43579) and four clinical isolates of H. pylori (Ed, A2, G1‐1, 5514) in the checkerboard assay and the fractional inhibitory concentration (FIC) index. A time–kill study was also performed on the strain ATCC 43579. The results showed that the E. torelliana extract inhibited the growth of all H. pylori strains, and the addition of one of the isolated active compounds, namely compound 2 (a substituted pyrenyl ester) enhanced the activity of clarithromycin. The minimum inhibitory concentration values of clarithromycin and the botanical compound were reduced twofold (from 0.125 to 0.0625 µg/mL and > 100 to 50 µg/mL respectively). A 100% reduction in CFU/mL of H. pylori ATCC 43579 was observed with the combination of 0.25 µg/mL clarithromycin and 100 µg/mL and 200 µg/mL compound 2 after 3 h of exposure. The results of the investigation showed that the combination of botanical compounds and antibiotics may be beneficial in the treatment of H. pylori infections. Copyright

In vitro susceptibility of Mycobacterium tuberculosis to extracts of Eucalyptus camaldulensis and Eucalyptus torelliana and isolated compounds

Context: Eucalyptus camaldulensis Dehnh. (Myrtaceae) and Eucalyptus torelliana F. Muell are used in Nigerian traditional medicine for the treatment of cough associated with tuberculosis (TB) and other respiratory infections. Objective: Hexane, chloroform, methanol extracts, and isolated compounds of E. camaldulensis and E. torelliana were screened for activity against Mycobacterium tuberculosis H37Rv (MtbH37Rv) to authenticate the traditional use of these plants. Materials and methods: The microplate alamar blue assay (MABA) method was used to investigate the anti-M. tuberculosis activities. Bioassay-guided fractionation of the hexane extract of E. torelliana leaf was performed, and isolated compounds were characterized by MS, 1D- and 2D-NMR. Results: The extracts inhibited the growth of MtbH37Rv [minimum inhibitory concentration (MIC) 4–64 µg/mL]. Spectroscopic characterization led to the identification of two compounds, hydroxymyristic acid methylester (1) and a substituted pyrenyl ester, a sterol (2). Compounds 1 and 2 had MIC of 49.45 and 46.99 µg/mL; IC50 >100 and 38.21 µg/mL; selectivity index (SI) >2.02 and 0.81, respectively, and a minimum bactericidal concentration (MBC) of 62.50 µg/mL. Discussion and conclusions: The anti-TB activities of these plants on M. tuberculosis H37Rv support their use in traditional medicine for the treatment of coughs associated with TB and reveals the presence of anti-Mtb active compounds in the plants. These findings not only demonstrate a new potential area of therapeutic value of E. camaldulensis and E. torelliana, but also illustrate the role of esters as anti-Mtb active principles in ethnobotanical preparations and as lead compounds in the development of new and effective anti-Mtb drugs.