Differently substituted flavanones were isolated from Leguminosae and their antibacterial activity was comparatively studied against methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentrations (MICs) of phytochemical flavanones to clinical isolates of MRSA were determined by a serial agar dilution method. The structure-activity relationship has indicated that 2',4'- or 2',6'-dihydroxylation of the B ring and 5,7-dihydroxylation of the A ring in the flavanone structure are important for significant anti-MRSA activity and that substitution with a certain aliphatic group at the 6- or 8-position also enhances the activity. Among the thirteen flavanones tested, tetrahydroxyflavanones with these structural characteristics isolated from Sophora exigua and Echinosophora koreensis showed intensive activity to inhibit the growth of all MRSA strains at 3.13-6.25 micrograms/ml. The present hydroxyflavanones would be useful in the phytotherapeutic strategy against MRSA infections.

Comparative Study on the Antibacterial Activity of Phytochemical Flavanones against Methicillin-resistant Staphylococcus aureus.

A wide range of medicinal and aromatic plants (MAPs) have been explored for their essential oils in the past few decades. Essential oils are complex volatile compounds, synthesized naturally in different plant parts during the process of secondary metabolism. Essential oils have great potential in the field of biomedicine as they effectively destroy several bacterial, fungal, and viral pathogens. The presence of different types of aldehydes, phenolics, terpenes, and other antimicrobial compounds means that the essential oils are effective against a diverse range of pathogens. The reactivity of essential oil depends upon the nature, composition, and orientation of its functional groups. The aim of this article is to review the antimicrobial potential of essential oils secreted from MAPs and their possible mechanisms of action against human pathogens. This comprehensive review will benefit researchers who wish to explore the potential of essential oils in the development of novel broad-spectrum key molecules against a broad range of drug-resistant pathogenic microbes.

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Antimicrobial Properties of Plant Essential Oils against Human Pathogens and Their Mode of Action: An Updated Review.

Green tea and grape seed extracts — Potential applications in food safety and quality

Chemical composition and antibacterial and antioxidant properties of commercial essential oils

Oxidative processes and meat spoilage bacteria are major contributors to decreasing the shelf-life of meat and meat products. Oxidative processes occur during processing, storage, and light exposure, lowering the nutritional and sensory value and acceptability of meat and generating toxic compounds for humans. Polyphenols inhibit oxidative processes in 3 ways: as reactive species scavengers, lipoxygenase inhibitors, and reducing agents for metmyoglobin. Thus, polyphenols are candidate antioxidants for meat and meat products. The cross-contamination of meat with spoilage and pathogenic microorganisms can occur in production lines and result in economic losses. The ability of polyphenols to interact with bacterial cell wall components and the bacterial cell membrane can prevent and control biofilm formation, as well as inhibit microbial enzymes, interfere in protein regulation, and deprive bacterial cell enzymes of substrates and metal ions. Thus, polyphenols are candidate antimicrobial agents for use with meat and meat products. Commercially available polyphenols can decrease primary and secondary lipid peroxidation levels, inhibit lipoxygenase activity, improve meat color stability, minimize the degradation of salt-soluble myofibrillar protein and sulfhydryl groups, and retard bacterial growth. Further studies are now needed to clarify the synergistic/antagonistic action of various polyphenols, and to identify the best polyphenol classes, concentrations, and conditions of use.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/1541-4337.12298

Plant Polyphenols as Antioxidant and Antibacterial Agents for Shelf-Life Extension of Meat and Meat Products: Classification, Structures, Sources, and Action Mechanisms

Chemical composition and antimicrobial activity of the essential oil of Coriandrum sativum.

In the present study, twelve different types of commercial tea samples were assayed to determine their phenolic composition and antioxidant activity. Reverse phase high performance liquid chromatography using a binary gradient system was used for the identification and quantification of individual catechins. Subsequently, total phenolic content was determined spectrophotometrically according to the Folin-ciocalteus method. Total theaflavins and thearubigins were also determined. The radical scavenging behavior of the polyphenols on 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) was also studied spectrophotometrically. The results showed that total polyphenols, total catechins and antioxidant activity were significantly (P<0.05) different in the commercial tea samples. Green tea had the highest levels of catechins, total polyphenols and total antioxidant activity. White tea (silvery tip) a rare specialty type of tea was not significantly different from green tea. Statistical analysis showed an essential catechin content influence of the tea extracts on antioxidant activity. Epigallocatechin gallate (EGCG) was the most potent catechin and the most potent in antioxidant activity (r = 0.989***). Epigallocatechin (EGC) (r = 0.787, P<0.001), epicatechin (EC) + catechin (+C) and epicatechigallate (ECG) also showed significant (P<0.05) antioxidant activity. Black tea contained high levels of theaflavins and thearubigins, which accounted for most of the antioxidant potential in this type of tea product (r = 0.930*** and r = 0.930*** respectively). These results suggest that conversion of catechins during black tea processing did not affect the free-radical potency of black tea. Gallic acid (GA) also showed significant(r = 0.530*) contribution to the antioxidant activity in black tea. Green, black and white tea products processed from Kenyan tea cultivars originally selected for black tea had significantly (P<0.05) higher antioxidant activity than green tea processed from tea cultivars from Japan and China. These results seem to suggest that the cultivar type is critical in determining the antioxidant potency of tea product and that black teas processed from suitable cultivars could be potent in antioxidant activity when compared to green teas.

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Antioxidant capacity of different types of tea products

This study investigated the phytochemical constituents and antimicrobial activity of hexane, ethyl acetate, dichloromethane and methanol leave extracts of Amaranthus hybridus, Amaranthus spinosus and Amaranthus caudatus. The microorganisms assayed for antimicrobial activity were: the grampositive Staphylococcus aureus and Bacillus spp, the gram-negative Escherichia coli, Salmonella typhi, Pseudomonas aeruginosae, Proteus mirabillis and Klebsiella pneumoniae and a pathogenic fungus Candida albicans. The leave extracts showed a broad spectrum anti-bacterial activity but resistance to the fungus. Commonly encountered phytochemical constituents in the leaf extracts of the three Amaranthus species included flavonoids, steroids, terpenoids and cardiac glycosides. The minimum inhibitory concentration (MIC) exhibited by A. spinosus extracts against the Salm. typhi was 129 mg/ml. The MIC exhibited by A. hybridus extracts against the tested organisms ranged between 200 and 755 mg/ml whereas that of A. caudatus was between 162.2 and 665 mg/ml. The antimicrobial properties of these plants which have been used by mankind for centuries without any signs of toxicity can be used in the traditional herbal medicines which play a very important role in primary care systems in the developing world and are becoming increasingly popular in the developed world.

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Phytochemical constituents and antimicrobial activity of leaf extracts of three Amaranthus plant species

Tsetse flies are notoriously difficult to observe in nature, particularly when populations densities are low. It is therefore difficult to observe them on their hosts in nature; hence their vertebrate species can very often only be determined indirectly by analysis of their gut contents. This knowledge is a critical component of the information on which control tactics can be developed. The objective of this study was to determine the sources of tsetse bloodmeals, hence investigate their feeding preferences. We used mitochondrial cytochrome c oxidase 1 (COI) and cytochrome b (cytb) gene sequences for identification of tsetse fly blood meals, in order to provide a foundation for rational decisions to guide control of trypanosomiasis, and their vectors. Glossina swynnertoni were sampled from Serengeti (Tanzania) and G. pallidipes from Kenya (Nguruman and Busia), and Uganda. Sequences were used to query public databases, and the percentage identities obtained used to identify hosts. An initial assay showed that the feeds were from single sources. Hosts identified from blood fed flies collected in Serengeti ecosystem, included buffaloes (25/40), giraffes (8/40), warthogs (3/40), elephants (3/40) and one spotted hyena. In Nguruman, where G. pallidipes flies were analyzed, the feeds were from elephants (6/13) and warthogs (5/13), while buffaloes and baboons accounted for one bloodmeal each. Only cattle blood was detected in flies caught in Busia and Uganda. Out of four flies tested in Mbita Point, Suba District in western Kenya, one had fed on cattle, the other three on the Nile monitor lizard. These results demonstrate that cattle will form an integral part of a control strategy for trypanosomiasis in Busia and Uganda, while different approaches are required for Serengeti and Nguruman ecosystems, where wildlife abound and are the major component of the tsetse fly food source.

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R. M. Ngure

Papers

Chemical composition and antimicrobial activity of the essential oil of Coriandrum sativum.

Antioxidant capacity of different types of tea products

Phytochemical constituents and antimicrobial activity of leaf extracts of three Amaranthus plant species

Tracking the feeding patterns of tsetse flies (Glossina genus) by analysis of bloodmeals using mitochondrial cytochromes genes.

Different types of tea products attenuate inflammation induced in Trypanosoma brucei infected mice