Natural Substances for the Synthesis of Silver Nanoparticles against Escherichia coli

The development of drug-resistant strains is rising and the search for new and novel ways of fighting new or reemerging microbes goes on. A hope of treating such multidrug-resistant infections came from plants mediated nanoparticles since nature is a generous source which provides a variety of chemical compounds that can be used for new drug discovery. Silver nanoparticles are reported to possess antiviral, antibacterial, antifungal, antiparasitic, larvicidal activity and anticancer properties. We reported green synthesis of silver nanoparticles mediated food plants Megaphrynium macrostachyum, Corchorus olitorus, Ricinodendron heudelotii, Gnetum bucholzianum, and Ipomoea batatas and their antibacterial efficacy against the Enterobacteriaceae Escherichia coli. The nature and size of the obtained nanoparticles are discussed as well as their Minimum Inhibitory Concentration (MIC) and the Minimum Bactericide Concentration (MBC) values considering their application in medical industry

Safety Assessment of Glyphaea brevis Spreng. (Tiliaceae): Acute and Subacute Toxicity of the Leaf Aqueous Extract in Mice and Wistar Rats

Background: Despite the various medicinal applications of Glyphaea brevis, no toxicology data are available that could guarantee its safety or describe its possible toxic effects. We studied the acute and subacute toxicity of leaf aqueous extract of G. brevis (GbAE) in animal models. Materials and methods: In acute toxicity study, mice were given a single oral administration of GbAE at doses of 1000, 2000 and 5000 mg/kg body weight (bw). The animals were monitored for behavioral changes and possible mortality over a 48-hour period, thereafter for 14 days. In the subacute toxicity study, rats were administered G. brevis extract at doses of 300, 600 and 1200 mg/kg bw daily, for 28 days. Tissue specimens of the liver and kidneys were subjected to histological examination using standard hematoxylin-eosin staining. An array of hematological (blood cells count and morphology) and biochemical assessments of blood (ALT, AST, urea, uric acid and creatinine) were performed. Results: In acute toxicity study, GbAE at a dose of 5000 mg/kg caused some signs of toxicity and mortality was higher in males than in females. Subacute toxicity study revealed that GbAE at a dose of 1200 mg/kg caused significant increase of lymphocytes rate as well as serum rates of ALT and creatinin. Microscopically, there were slight hepatic and renal tissue inflammation that was reversible. Conclusion: Some caution should be taken when G. brevis leaves are to be administered repetitively for long periods. Additional preclinical toxicological data should be acquired and ascertained over repeated long-term studies. Keywords: Glyphaea brevis, toxicity, histopathology, liver, kidne

Chemical Composition and Synergistic Antimicrobial Effects of a Vegetatively Propagated Cameroonian Lemon, Citrus x limon (L.) Osbeck

Nsangou MF, Happi EN, Fannang SV, et al. Chemical Composition and Synergistic Antimicrobial Effects of a Vegetatively Propagated Cameroonian Lemon, Citrus x limon (L.) Osbeck. ACS Food Science & Technology. 2021.This study analyzed the antimicrobial effects of compounds present in the roots and leaves of Citrus x limon (L.) Osbeck to help understand how this plant (1) ecologically modulates microbial defense in the rhizosphere and (2) protects against food-borne bacterial pathogens. Antimicrobial effects of C. limon collected from a farm in Foumban in Cameroon are reported against Salmonella typhi, Salmonella typhimurium, Salmonella enteritidis, Escherichia coli, Shigella flexineri, and Saccharomyces cerevisiae. The study modeled synergistic antifungal effects of an essential oil from the roots of C. limon or E-caryophyllene when combined with the isolated compounds against S. cerevisiae. Twenty-four compounds were identified from the methanol extracts of the roots and leaves: 10 prenylated coumarins (1–10), six methoxylated flavones (11–16), two limonoids (18 and 19), a phenylalanine derivative (20), lupeol, stigmasterol, sitosterol, and sitosterol-3-O-β-d-glucoside. Major compound 16, atalantoflavone, was esterified using lauric acid to yield the undescribed 5,4′-dilaureate atalantoflavone (16a). The essential oil from the roots contained methyl esters of hexadecanoic acid (39%) and 9-octadecenoic acid (9.3%) and sesquiterpenes β-bisabolene (10.1%) and α-santalene (8.0%). The antimicrobial effects of the root extract, leaf extract, compounds 1, 2, 4, 7–9, 11, 12, 14, 16, 16a, and 18 were evaluated against S. typhi, S. typhimurium, S. enteritidis, E. coli, S. flexineri, and S. cerevisiae. Compounds 11, 16, and 18 from the root extract of C. x limon showed significant antimicrobial effects with a minimum inhibitory concentration (MIC) of 62.5 μg/mL against S. flexineri, whereas compounds 5, 7, 11, and 18 showed significant antimicrobial effects with a MIC of 62.5 μg/mL against S. typhi. The essential oil from the roots synergized compounds 11–14 against S. cerevisiae. A synergistic MIC of 7.8 μg/mL was registered by combining 12 and E-caryophyllene

In vitro antimicrobial activity of the methanol extract and compounds from the wood of Ficus elastica Roxb. ex Hornem. aerial roots

Ficus elastica Roxb. ex Hornem., an edible plant belonging to the family of Moraceae, is traditionally used against skin infections and allergies besides having diuretic properties. This study aimed at investigating the antimicrobial activity of the wood of F. elastica aerial roots against a set of bacteria (Staphylococcus aureus; Escherichia coli, Proteus vulgaris, Providencia stuartii and Pseudomonas aeruginosa) and a yeast (Candida albicans). A mixture of linear aliphatic alkanes with n-hexacosane as major compound, β-sitosterol, biochanin A, sitosteryl 3-O-β-D-glucopyranoside (1), elasticamide (2), elastiquinone (3) and ficusoside B (4) were purified and characterized. Antimicrobial activities, expressed as minimum inhibitory concentration (MIC), indicated that the methanol extract showed MIC of 39.1 μg/mL; the lowest values were obtained for 3 and 4, with MIC as low as 4.9 μg/mL, smaller than the values of reference antibiotics (25 μg/mL). Furthermore, as most of the studied samples exhibited Minimum Microbicidal Concentration/Minimum Inhibitory Concentration (MMC/MIC) ratios lower than 4, a microbicidal effect was clearly exhibited. The overall results provided evidence that the wood of F. elastica aerial roots, as well as some of its isolated components might be potential sources of new antimicrobial drugs