Antimicrobial activity of flavonoids

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

Advances in flavonoid research since 1992.

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

Flavonoids, a group of natural substances with variable phenolic structures, are found in fruits, vegetables, grains, bark, roots, stems, flowers, tea and wine. These natural products are well known for their beneficial effects on health and efforts are being made to isolate the ingredients so called flavonoids. Flavonoids are now considered as an indispensable component in a variety of nutraceutical, pharmaceutical, medicinal and cosmetic applications. This is attributed to their anti-oxidative, anti-inflammatory, anti-mutagenic and anti-carcinogenic properties coupled with their capacity to modulate key cellular enzyme function. Research on flavonoids received an added impulse with the discovery of the low cardiovascular mortality rate and also prevention of CHD. Information on the working mechanisms of flavonoids is still not understood properly. However, it has widely been known for centuries that derivatives of plant origin possess a broad spectrum of biological activity. Current trends of research and development activities on flavonoids relate to isolation, identification, characterisation and functions of flavonoids and finally their applications on health benefits. Molecular docking and knowledge of bioinformatics are also being used to predict potential applications and manufacturing by industry. In the present review, attempts have been made to discuss the current trends of research and development on flavonoids, working mechanisms of flavonoids, flavonoid functions and applications, prediction of flavonoids as potential drugs in preventing chronic diseases and future research directions.

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Flavonoids: an overview

Antioxidative and superoxide scavenging activities of retrochalcones in Glycyrrhiza inflata.

Antioxidant components in Aloe vera were examined for lipid peroxidation using rat liver microsomal and mitochondrial enzymes. Among the aloesin derivatives examined, isorabaichromone showed a potent antioxidative activity. The DPPH radical and superoxide anion scavenging activities were determined. As one of the most potent components, isorabaichromone together with feruloylaloesin and p-coumaroylaloesin showed potent DPPH radical and superoxide anion scavenging activities. Electron spin resonance (ESR) using the spin trapping method suggested that the potent superoxide anion scavenging activity of isorabaichromone may have been due to its caffeoyl group. As A. vera has long been used to promote wound healing, the inhibitory effects of aloesin derivatives for cyclooxygenase (Cox)-2 and thromboxane (Tx) A 2 synthase were examined and the participation of p-coumaroyl and feruloyl ester groups in the aloesin skeleton was demonstrated. These findings may explain, at least in part, the wound healing effects of A.vera. Abbreviations. ADP:adenosine diphosphate ASA:ascorbic acid BHT:butylated hydroxytoluene BSA:bovine serum albumin DMPO:5,5-dimethyl-1-pyrroline N-oxide DPPH:1,1-diphenyl-2-picrylhydrazyl EDTA:edetic acid HEPES: N-(2-hydroxyethyl)-piperazine- N-2'-ethane-sulfonic acid NADH:reduced nicotinamide adenine dinucleotide NADPH:reduced nicotinamide adenine dinucleotide phosphate NBT:nitroblue tetrazolium Pg:prostaglandin SOD:superoxide dismutase TBA:thiobarbituric acid TCA:trichloroacetic acid XOD:xanthine oxidase

Antioxidant, free radical scavenging and anti-inflammatory effects of aloesin derivatives in Aloe vera.

Mode of antibacterial action of retrochalcones from Glycyrrhiza inflata

Four diterpenoids, carnosic acid (1), carnosol (2), rosmanol (3), and epirosmanol (4), were isolated as antioxidative agents from the leaves of Rosmarinus officinalis by bioassay-directed fractionation. These diterpenoids inhibited superoxide anion production in the xanthine/xanthine oxidase system. Mitochondrial and microsomal lipid peroxidation induced by NADH or NADPH oxidation were also completely inhibited by these diterpenes at the concentration of 3-30 microM. Furthermore, carnosic acid protected red cells against oxidative hemolysis. These phenolic diterpenes were shown to be effective to protect biological systems against oxidative stresses.

Inhibition of lipid peroxidation and superoxide generation by diterpenoids from Rosmarinus officinalis.

Four sesquiterpenoids, beta-caryophyllene, beta-caryophyllene 4,5 alpha-oxide, 7-hydroxy-3,4-dihydrocadalin, and 7-hydroxycadalin, isolated from the dried flower of Heterotheca inuloides Cass. (Asteraceae), have been found to exhibit cytotoxic activity against several solid tumor cell lines. Among them, 7-hydroxy-3,4-dihydrocadalin and 7-hydroxycadalin have also been found to inhibit autoxidative and microsomal lipid peroxidation.

Hiroyuki Haraguchi

Papers

Antioxidative and superoxide scavenging activities of retrochalcones in Glycyrrhiza inflata.

Antioxidant, free radical scavenging and anti-inflammatory effects of aloesin derivatives in Aloe vera.

Mode of antibacterial action of retrochalcones from Glycyrrhiza inflata

Inhibition of lipid peroxidation and superoxide generation by diterpenoids from Rosmarinus officinalis.

Cytotoxic and antioxidative sesquiterpenoids from Heterotheca inuloides