http://www.dietcan.net/docs/Polifenoles%20en%20alimentos%20y%20biodisponibilidad.pdf

Polyphenols: food sources and bioavailability

Antimicrobial activity of flavonoids

Flavonoids are a class of secondary plant phenolics with significant antioxidant and chelating properties. In the human diet, they are most concentrated in fruits, vegetables, wines, teas and cocoa. Their cardioprotective effects stem from the ability to inhibit lipid peroxidation, chelate redox-active metals, and attenuate other processes involving reactive oxygen species. Flavonoids occur in foods primarily as glycosides and polymers that are degraded to variable extents in the digestive tract. Although metabolism of these compounds remains elusive, enteric absorption occurs sufficiently to reduce plasma indices of oxidant status. The propensity of a flavonoid to inhibit free-radical mediated events is governed by its chemical structure. Since these compounds are based on the flavan nucleus, the number, positions, and types of substitutions influence radical scavenging and chelating activity. The diversity and multiple mechanisms of flavonoid action, together with the numerous methods of initiation, detection and measurement of oxidative processes in vitro and in vivo offer plausible explanations for existing discrepancies in structure-activity relationships. Despite some inconsistent lines of evidence, several structure-activity relationships are well established in vitro. Multiple hydroxyl groups confer upon the molecule substantial antioxidant, chelating and prooxidant activity. Methoxy groups introduce unfavorable steric effects and increase lipophilicity and membrane partitioning. A double bond and carbonyl function in the heterocycle or polymerization of the nuclear structure increases activity by affording a more stable flavonoid radical through conjugation and electron delocalization. Further investigation of the metabolism of these phytochemicals is justified to extend structure-activity relationships (SAR) to preventive and therapeutic nutritional strategies.

Flavonoid antioxidants: chemistry, metabolism and structure-activity relationships.

Publisher Summary This chapter discusses ferric reducing/antioxidant power (FRAP) assay. The ferric reducing/antioxidant power (FRAP) assay is a recently developed, direct test of “total antioxidant power.” The FRAP assay is robust, sensitive, simple, and speedy and facilitates experimental and clinical studies investigating the relationship among antioxidant status, dietary habits, and risk of disease. Measurement of the total antioxidant power of fresh biological fluids—such as blood plasma—can be measured directly; the antioxidant content of various dietary agents can be measured objectively and reproducibly and their potential for improving the antioxidant status of the body investigated and compared. The FRAP assay is also sensitive and analytically precise enough to be used in assessing the bioavailability of antioxidants in dietary agents to help monitor longitudinal changes in antioxidant status associated with an increased intake of dietary antioxidants and to investigate the effects of disease on antioxidant status.

Ferric reducing/antioxidant power assay: direct measure of total antioxidant activity of biological fluids and modified version for simultaneous measurement of total antioxidant power and ascorbic acid concentration

The antioxidant capacities (oxygen radical absorbance capacity, ORAC) and total phenolic contents in extracts of 27 culinary herbs and 12 medicinal herbs were determined. The ORAC values and total phenolic contents for the medicinal herbs ranged from 1.88 to 22.30 μmol of Trolox equivalents (TE)/g of fresh weight and 0.23 to 2.85 mg of gallic acid equivalents (GAE)/g of fresh weight, respectively. Origanum × majoricum, O. vulgare ssp. hirtum, and Poliomintha longiflora have higher ORAC and phenolic contents as compared to other culinary herbs. The ORAC values and total phenolic content for the culinary herbs ranged from 2.35 to 92.18 μmol of TE/g of fresh weight and 0.26 to 17.51 mg of GAE/g of fresh weight, respectively. These also were much higher than values found in the medicinal herbs. The medicinal herbs with the highest ORAC values were Catharanthus roseus, Thymus vulgaris, Hypericum perforatum, and Artemisia annua. A linear relationship existed between ORAC values and total phenolic contents of th...

Antioxidant activity and phenolic compounds in selected herbs

The antioxidative activity of a total of 92 phenolic extracts from edible and nonedible plant materials (berries, fruits, vegetables, herbs, cereals, tree materials, plant sprouts, and seeds) was examined by autoxidation of methyl linoleate. The content of total phenolics in the extracts was determined spectrometrically according to the Folin-Ciocalteu procedure and calculated as gallic acid equivalents (GAE). Among edible plant materials, remarkable high antioxidant activity and high total phenolic content (GAE > 20 mg/g) were found in berries, especially aronia and crowberry. Apple extracts (two varieties) showed also strong antioxidant activity even though the total phenolic contents were low (GAE < 12.1 mg/g). Among nonedible plant materials, high activities were found in tree materials, especially in willow bark, spruce needles, pine bark and cork, and birch phloem, and in some medicinal plants including heather, bog-rosemary, willow herb, and meadowsweet. In addition, potato peel and beetroot peel extracts showed strong antioxidant effects. To utilize these significant sources of natural antioxidants, further characterization of the phenolic composition is needed.

Antioxidant activity of plant extracts containing phenolic compounds

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

https://jeffreydachmd.com/wp-content/uploads/2016/02/What-made-sesquiterpene-lactones-reach-cancer-clinical-trials-Ghantous-Akram-2010.pdf

What made sesquiterpene lactones reach cancer clinical trials

http://www.uniroma2.it/didattica/piante_medicinali/deposito/coumarin.pdf

Antimicrobial activity of some coumarin containing herbal plants growing in Finland.

Natural derived or originated compounds still play a major role as drugs, and as lead structures for the development of synthetic molecules. About 50% of the drugs introduced to the market during the last 20 years are derived directly or indirectly from small biogenic molecules. In the future, natural products will continue to play a major role as active substances, model molecules for the discovery and validation of drug targets. A multidisciplinary approach to drug discovery involving the generation of truly novel molecular diversity from natural product sources, combined with total and combinatorial synthetic methodologies provides the best solution to increase the productivity in drug discovery and development. Screening for new drugs in plants implies the screening of extracts for the presence of novel compounds and an investigation of their biological activities. It is currently estimated that approximately 420,000 plant species exist in nature. For the purpose of lead discovery, or for the scientific validation of a traditional medicinal plant or a phytopharmaceutical, active principals in complex matrices need to be identified. Therefore, the interfacing of biological and chemical assessment becomes the critical issue. Drug discovery from plants can be guided by epidemiologic studies facilitated with computer assisted HPLC microfractionation and microplate technology. Epidemiologic studies have shown that high dietary flavonoid intake may be associated with decreased risk for cardiovascular disease. Chlamydia pneumoniae is a common human pathogen and epidemiological and clinical studies have shown a connection between chronic C. pneumoniae infection, atherosclerosis and the risk of myocardial infarction. We will present here the detection of natural compounds active against C. pneumoniae as an example.

Heikki Vuorela

Papers

Antioxidant activity of plant extracts containing phenolic compounds

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

What made sesquiterpene lactones reach cancer clinical trials

Antimicrobial activity of some coumarin containing herbal plants growing in Finland.

Natural Products in the Process of Finding New Drug Candidates