Antimicrobial natural products: an update on future antibiotic drug candidates

Plant cell and tissue cultures can be established routinely under sterile conditions from explants, such as plant leaves, stems, roots, meristems etc for both the ways for multiplication and extraction of secondary metabolites. Strain improvement, methods for the selection of high-producing cell lines, and medium optimizations can lead to an enhancement in secondary metabolite production. However, most often trials with plant cell cultures fail to produce the desired products. In such cases, strategies to improve the production of secondary metabolites must be considered. One of the main problems encountered is the lack of basic knowledge of the biosynthetic routes, and mechanisms responsible for the production of plant metabolites. Where the productivity of the desired metabolites is limited by the lack of particular precursors, biotransformation using an exogenous supply of biosynthetic precursors, genetic manipulation and metabolic engineering may improve the accumulation of compounds. Feedback inhibition of metabolic enzymes as well as inhibition of membrane transport can be eliminated by the accumulation of synthesized products in a second phase introduced into the aqueous medium. Organ cultures and in vitro biomass production often have sites of synthesis and storage of secondary metabolites in separate compartments. Elicitors, compounds triggering the formation of secondary metabolites, can be abiotic or biotic. Natural elicitors include polysaccharides such as pectin and chitosan, which are also used in the immobilization and permeabilization of plant cells. Immobilization with suitable bioreactor system provides several advantages, such as continuous process operation, but for the development of an immobilized plant cell culture process, natural or artifically induced secretion of the accumulated product into the surrounding medium is necessary. The present review highlights the nature, applications, perspective and scale up methods for the production of valuable secondary metabolites in vitro.

	 

	Key words: Plant cell cultures, secondary metabolites, biotransformation, biosynthetic pathways, elicitation, immobilization, bioreactors.

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A review on trends in production of secondary metabolites from higher plants by in vitro tissue, organ and cell cultures.

The growing demand for natural food preservatives in the last decade has promoted investigations on their application for preserving perishable foods. In this context, the present review is focused on discussing the prospective application of plant extracts containing phenolics or isolated plant phenolics as natural antimicrobials in foods. Plant essential oils are outside the scope of this review since utilization of their antimicrobial activity for food preservation has been extensively reviewed.; Results: Although the exact antimicrobial mechanisms of action of phenolic compounds are not yet fully understood, it is commonly acknowledged that they have diverse sites of action at the cellular level. Antimicrobial phenolics can be added directly to the formulation of perishable food products or incorporated into food-contact materials to release them in the immediate zone of perishable foods. Edible coatings or active food packaging materials can thus be used as carriers of plant bioactive compounds.; Conclusion: These materials could be an interesting delivery system to improve the stability of phenolics in foods and to improve the shelf life of perishable foods. This review will thus provide an overview of current knowledge of the antimicrobial activity of phenolic-rich plant extracts and of the promises and limits of their exploitation for the preservation of perishable foods. © 2018 Society of Chemical Industry.; © 2018 Society of Chemical Industry.

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Plant antimicrobial polyphenols as potential natural food preservatives

The large surface area and ability to retain moisture of textile structures enable microorganisms' growth, which causes a range of undesirable effects, not only on the textile itself, but also on the user. Due to the public health awareness of the pathogenic effects on personal hygiene and associated health risks, over the last few years, intensive research has been promoted in order to minimize microbes' growth on textiles. Therefore, to impart an antimicrobial ability to textiles, different approaches have been studied, being mainly divided into the inclusion of antimicrobial agents in the textile polymeric fibers or their grafting onto the polymer surface. Regarding the antimicrobial agents, different types have been used, such as quaternary ammonium compounds, triclosan, metal salts, polybiguanides or even natural polymers. Any antimicrobial treatment performed on a textile, besides being efficient against microorganisms, must be non-toxic to the consumer and to the environment. This review mainly intends to provide an overview of antimicrobial agents and treatments that can be performed to produce antimicrobial textiles, using chemical or physical approaches, which are under development or already commercially available in the form of isolated agents or textile fibers or fabrics.

https://www.mdpi.com/1996-1944/9/6/498/pdf

Antimicrobial Approaches for Textiles: From Research to Market

The emergence of antibiotic resistance in pathogenic bacteria has led to renewed interest in exploring the potential of plant-derived antimicrobials (PDAs) as an alternative therapeutic strategy to combat microbial infections. Historically, plant extracts have been used as a safe, effective, and natural remedy for ailments and diseases in traditional medicine. Extensive research in the last two decades has identified a plethora of PDAs with a wide spectrum of activity against a variety of fungal and bacterial pathogens causing infections in humans and animals. Active components of many plant extracts have been characterized and are commercially available; however, research delineating the mechanistic basis of their antimicrobial action is scanty. This review highlights the potential of various plant-derived compounds to control pathogenic bacteria, especially the diverse effects exerted by plant compounds on various virulence factors that are critical for pathogenicity inside the host. In addition, the potential effect of PDAs on gut microbiota is discussed.

/pdf/combating-pathogenic-microorganisms-using-plant-derived-45t5vrwkzh.pdf

Combating pathogenic microorganisms using plant-derived antimicrobials: a minireview of the mechanistic basis.

Antifungal anthraquinones from Saprosma fragrans.

Antifungal activity of Agapanthus africanus extractives

A new 3,4-dihydroxy-1-methoxy anthraquinone-2-corboxaldehyde (1) together with a known anthraquinone, damnacanthal (2), were isolated from the chloroform fraction of the aerial part (whole plant without root) of Saprosma fragrans. The isolated anthraquinones (1) and (2) were found to exhibit antifungal activity against Trichophyton mentagrophytes and Sporitrichum schenckii. Their structures were established by chemical and spectral analysis.

D.N. Singh

Papers

Antifungal anthraquinones from Saprosma fragrans.

Antifungal activity of Agapanthus africanus extractives

Antifungal Anthraquinones from Saprosma fragrans.

Sesquiterpene lactones of Saussurea lappa (Decne.) Sch.Bip, and comparative antimicrobial activity of its root oil and extracts