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

Antimicrobial activity of flavonoids

Antimicrobial effects of Finnish plant extracts containing flavonoids and other phenolic compounds

Phytochemicals, as plant components with discrete bio-activities towards animal biochemistry and metabolism are being widely examined for their ability to provide health benefits. It is important to establish the scientific rationale to defend their use in foods, as potential nutritionally active ingredients. Phytochemicals could provide health benefits as: (1) substrates for biochemical reactions; (2) cofactors of enzymatic reactions; (3) inhibitors of enzymatic reactions; (4) absorbents/sequestrants that bind to and eliminate undesirable constituents in the intestine; (5) ligands that agonize or antagonize cell surface or intracellular receptors; (6) scavengers of reactive or toxic chemicals; (7) compounds that enhance the absorption and or stability of essential nutrients; (8) selective growth factors for beneficial gastrointestinal bacteria; (9) fermentation substrates for beneficial oral, gastric or intestinal bacteria; and (10) selective inhibitors of deleterious intestinal bacteria. Such phytochemicals include terpenoids, phenolics, alkaloids and fiber. Research supporting beneficial roles for phytochemicals against cancers, coronary heart disease, diabetes, high blood pressure, inflammation, microbial, viral and parasitic infections, psychotic diseases, spasmodic conditions, ulcers, etc is based on chemical mechanisms using in vitro and cell culture systems, various disease states in animals and epidemiology of humans. However, it must be emphasized that a distinction needs to be drawn between the types of information that can be obtained from studies in vitro, in animals and in humans. Mechanisms of action must certainly be established in vitro; however, the efficacy of these same ingredients with their mechanisms of action, must also be demonstrated in vivo. The rapid growth in the use of phytochemicals in nutraceutical and functional foods requires that the food and pharmaceutical industries face new challenges: in addressing worldwide public concern over the efficacy and safety of supplements and foods claimed to be health-promoting; in government regulations related to safety, labeling and health claims for products that contain phytochemicals; in the manufacturing of foods with different qualities and stabilities; and in marketing issues, particularly as they relate to consumers' recognizing added value.

© 2000 Society of Chemical Industry

Phytochemicals: nutraceuticals and human health.

https://zenodo.org/record/1003263/files/Cushnie%20et%20al%20%282011%29%20post-peer%20reviewed%20version.pdf

Recent advances in understanding the antibacterial properties of flavonoids

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.

Abstract Five novel oligostilbenes, named leachianols C-G, were isolated from the roots of Sophora leachiana . Their structures were established by means of 2D NMR spectroscopic analysis, including HMBC, COLOC and PSNOESY, to be a resveratrol tetramer with a 2-cyclohexen-4-one ring (leachianol C), a resveratrol trimer with a dihydrobenzofuran ring (leachianol D), a regioisomer of leachianol D (leachianol E), a resveratrol dimer (leachianol F) and a stereoisomer of leachianol F (leachianol G), respectively. These oligostilbenes in S. leachiana derived from pallidol are different from those in S. moorcroftiana , which are derived from e-viniferin.

Five Resveratrol Oligomers from Roots of Sophora leachiana.

Abstract Six novel flavonostilbenes, alopecurones A-F, were isolated from the roots of Sophora alopecuroides , in addition to a new 5-deoxyflavanone with a lavandulyl group, alopecurone G. The structures of alopecurones A-F, which are flavonostilbenes composed of a flavanone [5,7,2′,4′-tetrahydroxy-8-lavandulylfavanone (sophoraflavanone G) or its 2′-methyl ether (leachianone A)] condensed with a stilbene [3,5,4′-trihydroxystilbene (resveratrol)] through the A ring of the flavanone skeleton, were established by spectroscopic analysis. Chemical relationships between S. alopecuroides, S. leachiana and S. moorcroftiana are discussed on the basis of their phenolic components.

Tanaka

Papers

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

Five Resveratrol Oligomers from Roots of Sophora leachiana.

Six Flavonostilbenes and a Flavanone in Roots of Sophora alopecuroids.

Flavonoids in the Roots of Sophora prostrata.

A Prenylated Flavanone from Roots of Amorpha fruticosa.