Discovery, synthesis and antibacterial evaluation of phenolic compounds from Cylicodiscus gabunensis.

BACKGROUND: Cylicodiscus gabunensis Harms (Family Leguminosae) (CG) is an African medicinal plant used as a treatment of various ailments including malaria, liver diseases, and gastrointestinal disturbances. Its extracts showed potent in vitro antibacterial activity. However, the antibacterial components are unknown. METHODS: In this study, the stem bark of the CG plant was extracted and its antibacterial property against a panel of Gram-negative and Gram-positive bacterial strains assessed using the disk diffusion assay method. Bioassay-guided fractionation of the bioactive extracts was employed to identify bioactive constituents using both gas and liquid chromatography mass spectrometry. Chemical synthesis was used to make the analogues of gallic acid. Microplate dilution assays and scanning electron microscopy (SEM) were used to evaluate the antibacterial properties and mechanism of action of the active fractions and pure compounds. RESULTS: The most bioactive sub-fractions derived from CG comprised of ethyl gallate, gallic acid and polyphenols. Five alkyl/alkenyl gallates were synthesized. A preliminary structure-activity relationship of gallic acid derivatives was obtained using the synthetic analogues and a series of commercially available phenolic compounds. Increasing the length of alkyl chains generally increases the potency of the alkyl gallates. Introducing a double bond with restricted conformations of the C-5 side chain has little effect on the antibacterial property. SEM analysis of the effect of alkyl gallates on Staphylococcus aureus indicates that they appear to interrupt S. aureus bacterial cell wall integrity. CONCLUSIONS: The results of this research rationalise the ethnobotanical use of C. gabunensis and suggest that gallate derivatives may serve as promising antibacterial agents for the treatment of infectious diseases.

General Overview of Phenolics from Plant to Laboratory, Good Antibacterials or Not.

The emergence and rapid development of seriously drug-resistant pathogens have created the greatest danger to public health and made the treatment of infectious diseases ineffective; to control the antibiotic-resistant microbes, the discovery of new effective antibacterials with new mechanisms of action against bacteria remains an urgent task to control the bacterial resistance. The paucity of infections in wild plants supports the role of innate defense system of plants. Many researchers nominate the natural extracts to act against bacterial resistance mechanisms, and the majority of them have now been focused on the combination of plant extracts and antibiotics to define the availability of resistance modification agents. Only very few numbers of natural products are successful to reach experiments circle beyond the in vitro assays. Phenols and phenolic acids could serve as good candidates to the natural antibacterial arsenal. The pyrogallol-based compounds are more potent than others such as catechol or resorcinol, gallic acid, and the hydroxycinnamic acid (ferulic acid) are destructing the bacterial cell wall of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, leading to leakage of cellular contents. These compounds have stronger activity against Gram-positive microorganisms, and some of them showed good synergism with antibiotics, for example, pentagalloylglucopyranose, is shown a synergism with penicillin G against methicillin-resistant S. aureus, another example is the interesting synergism between epicatechin gallate and oxacillin where the minimal inhibitory concentrations of oxacillin reduced around 500 times by the addition of epicatechin gallate to the antibiotic.

Screening of Fruits of Seven Plants Indicated for Medicinal Use in Iraq.

INTRODUCTION: Coumarins exert many biological effects in humans, animals, and plants, which make the evaluation of their biological activities and study of their role in ethnomedicine highly valued. OBJECTIVES: Here, we selected seven plants which have ethnopharmacological use as antimicrobial in Iraq and the aims were to quantify the two structural isomers bergapten and methoxsalen in their seeds, to evaluate the antibacterial activities against several clinical isolates, and to isolate bergapten and methoxsalen from Ammi majus. MATERIALS AND METHODS: Seven plants were extracted by petroleum ether (PE) and ethanol (EtOH). Bergapten and methoxsalen were separated and purified by preparative thin-layer chromatography. Quantification of the furanocoumarins has been conducted by high-performance liquid chromatography, and all the plant extracts and pure compounds were checked for antibacterial activities utilizing alamar blue microplate assay. RESULTS: Cuminum cyminum was deprived of bergapten and methoxsalen and methoxsalen was not detected from Apium graveolens. Bergapten was abundant in PE more than in EtOH; on the other hand, EtOH was rich in methoxsalen. The separation of the two structural isomers was performed using normal phase chromatography and ultraviolet light as an indicator. All extracts showed weak to moderate antibacterial activities against Gram-positive isolates which were more sensitive than the negative ones. C. cyminum extract was least active, uncover the antibacterial role of bergapten and methoxsalen. CONCLUSION: These findings support the medicinal use of seeds of seven plants from Apiaceae family and quantify the two pharmacologically important furanocoumarins (bergapten and methoxsalen). SUMMARY: This study was conducted to evaluate the antibacterial activities of seven plants seeds used in local medicine in Iraq. High-performance liquid chromatography was used to quantify bergapten and xanthotoxin in non-polar and polar extracts of these seeds. This study supports the medicinal use of these plants and clarifies the role of bergapten and xanthotoxin in antibacterial activities of these plants. Abbreviations used: EtOH: Ethanol; MIC: Minimum inhibitory concentration; PE: Petroleum ether; Rf: Retardation factor; Rt: Retention time.

A characterization of the antimalarial activity of the bark of Cylicodiscus gabunensis Harms.

ETHNOPHARMACOLOGICAL RELEVANCE AND AIM: A decoction of the bark of Cylicodiscus gabunensis Harms is used as a traditional medicine in the treatment of malaria in Nigeria. This study aims to validate the antimalarial potency of this decoction in vitro against Plasmodium falciparum and define potential bioactive constituents within the C. gabunensis bark. MATERIALS AND METHODS: A bioassay-guided separation and fractionation protocol was applied to C. gabunensis extracts, exploiting the use of a Malaria Sybr Green I Fluorescence assay method to monitor antiproliferative effects on parasites as well as define 50% inhibition concentrations. Spectroscopic techniques, including GC-MS, TOF LC-MS and 1H NMR were used to identify phytochemicals present in bioactive fractions. Analogues of gallic acid were synthesized de novo to support the demonstration of the antimalarial action of phenolic acids identified in C. gabunensis bark. In vitro cytotoxicity of plant extracts, fractions and gallate analogues was evaluated against the HepG2 cell line. RESULTS: The antimalarial activity of ethanolic extracts of C. gabunensis bark was confirmed in vitro, with evidence for phenolic acids, primarily gallic acid and close analogues such as ethyl gallate, likely providing this effect. Further fractionation produced the most potent fraction with a 50% inhibitory concentration of 4.7µg/ml. Spectroscopic analysis, including 1H NMR, LC-MS and GC-MS analysis of this fraction and its acid hydrolyzed products, indicated the presence of conjugates of gallic acid with oligosaccharides. The extracts/fractions and synthetic alkyl and alkenyl gallates showed moderate selectivity against P. falciparum. CONCLUSIONS: These results support the use of the bark of C. gabunensis as a traditional medicine in the treatment of human malaria, with phenolic acid oligosaccharide complexes evident in the most bioactive fractions.