The use of and search for drugs and dietary supplements derived from plants have accelerated in recent years. Ethnopharmacologists, botanists, microbiologists, and natural-products chemists are combing the Earth for phytochemicals and “leads” which could be developed for treatment of infectious diseases. While 25 to 50% of current pharmaceuticals are derived from plants, none are used as antimicrobials. Traditional healers have long used plants to prevent or cure infectious conditions; Western medicine is trying to duplicate their successes. Plants are rich in a wide variety of secondary metabolites, such as tannins, terpenoids, alkaloids, and flavonoids, which have been found in vitro to have antimicrobial properties. This review attempts to summarize the current status of botanical screening efforts, as well as in vivo studies of their effectiveness and toxicity. The structure and antimicrobial properties of phytochemicals are also addressed. Since many of these compounds are currently available as unregulated botanical preparations and their use by the public is increasing rapidly, clinicians need to consider the consequences of patients self-medicating with these preparations.

Plant Products as Antimicrobial Agents

There has been increasing interest in the research on flavonoids from plant sources because of their versatile health benefits reported in various epidemiological studies. Since flavonoids are directly associated with human dietary ingredients and health, there is need to evaluate structure and function relationship. The bioavailability, metabolism, and biological activity of flavonoids depend upon the configuration, total number of hydroxyl groups, and substitution of functional groups about their nuclear structure. Fruits and vegetables are the main dietary sources of flavonoids for humans, along with tea and wine. Most recent researches have focused on the health aspects of flavonoids for humans. Many flavonoids are shown to have antioxidative activity, free radical scavenging capacity, coronary heart disease prevention, hepatoprotective, anti-inflammatory, and anticancer activities, while some flavonoids exhibit potential antiviral activities. In plant systems, flavonoids help in combating oxidative stress and act as growth regulators. For pharmaceutical purposes cost-effective bulk production of different types of flavonoids has been made possible with the help of microbial biotechnology. This review highlights the structural features of flavonoids, their beneficial roles in human health, and significance in plants as well as their microbial production.

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Chemistry and Biological Activities of Flavonoids: An Overview

https://www.cell.com/cell/pdf/0092-8674(94)90544-4.pdf

H2O2 from the oxidative burst orchestrates the plant hypersensitive disease resistance response

Nanomaterials, such as metal or semiconductor nanoparticles and nanorods, exhibit similar dimensions to those of biomolecules, such as proteins (enzymes, antigens, antibodies) or DNA. The integration of nanoparticles, which exhibit unique electronic, photonic, and catalytic properties, with biomaterials, which display unique recognition, catalytic, and inhibition properties, yields novel hybrid nanobiomaterials of synergetic properties and functions. This review describes recent advances in the synthesis of biomolecule-nanoparticle/nanorod hybrid systems and the application of such assemblies in the generation of 2D and 3D ordered structures in solutions and on surfaces. Particular emphasis is directed to the use of biomolecule-nanoparticle (metallic or semiconductive) assemblies for bioanalytical applications and for the fabrication of bioelectronic devices.

Integrated Nanoparticle–Biomolecule Hybrid Systems: Synthesis, Properties, and Applications

Studies of the molecular genetics, mechanisms of activation and functional connections between general phenylpropanoid metabolism and certain branch pathways in parsley, bean, potato plants and cell cultures

Physiology and Molecular Biology of Phenylpropanoid Metabolism

Phytoalexins: enzymology and molecular biology.

Biochemistry of Storage Carbohydrates in Green Plants

Publisher Summary Plant galactomannans are reserve polysaccharides composed of linear chains of (1→4)-linked β-D-mannopyranosyl residues having single stubs of α-D-galactopyranosyl groups joined by (1→6)-linkages along the chain These polysaccharides are widely used in industry especially in food, pharmaceuticals, cosmetics, paper products, paints and plasters, well-drilling and mining, and explosives and fire-fighting The distribution of galactomannans in the plant kingdom is limited The rich sources are the members of the family Leguminoseae In context to the biosynthesis of plant galactomannans, it is concluded that D-galactose is stored in the seeds in the form of galactomannan, by random attachment of D-galactosyl groups to a main-chain of D-mannan Seed galactomannans exhibits double physiological function Firstly, they retain water by solvation and thereby prevent complete drying of the seeds, which can cause protein denaturation— in particular—the denaturation of those enzymes essential for seed germination Secondly, the galactomannans serve as food reserves for the germinating seeds

Biochemistry of Plant Galactomannans

Publisher Summary This chapter provides an overview of plant cell-walls. The cell wall is an envelope that encases the plant cell. The wall must be rigid enough to give the plant strength and form, and yet, if necessary, it must yield freely to facilitate growth. The network of cell walls, where adjoining cells have a wall in common, provides in a plant the structural framework analogous to both the skin and the bones of an animal. In some plants, especially those having woody tissues, the strength of this cell-wall network is prodigious. However, despite their apparently tough sheathing, the cells of the growing regions of a plant are able to extend to many times their initial length. The cell wall lies outside the plasma membrane, which defines the boundaries of the cell itself. The wall is freely permeable to most molecules, but the membrane exhibits selective permeability tending to concentrate certain dissolved molecules and ions inside the cell. The presence of such charged components as acidic polysaccharides within the wall imparts ion-exchange properties to the wall. The chapter discusses the concepts related to the types of cell-wall polysaccharides and elaborates the methods used in the elucidation of primary-wall structure. It also presents an overview of cell-wall glycoproteins.

Plant Cell-Walls

Fruit ripening is associated with cell wall modifications. The present review focuses on cell wall components and the nature of noncovalent and covalent interactions in the primary cell wall. The role of structural protein cross-links are evaluated within the context of cell wall-mediated changes in texture during fruit ripening. The article discusses molecular approaches in fruit cell wall interactions to regulate processes in fruit ripening in order to improve post-harvest textural characteristics.

Prakash M. Dey

Papers

Phytoalexins: enzymology and molecular biology.

Biochemistry of Storage Carbohydrates in Green Plants

Biochemistry of Plant Galactomannans

Plant Cell-Walls

Molecular aspects of cell wall modifications during fruit ripening.