Flavonoids are a family of polyphenolic compounds which are widespread in nature (vegetables) and are consumed as part of the human diet in significant amounts. There are other types of polyphenols, including, for example, tannins and resveratrol. Flavonoids and related polyphenolic compounds have significant antiinflammatory activity, among others. This short review summarizes the current knowledge on the effects of flavonoids and related polyphenolic compounds on inflammation, with a focus on structural requirements, the mechanisms involved, and pharmacokinetic considerations. Different molecular (cyclooxygenase, lipoxygenase) and cellular targets (macrophages, lymphocytes, epithelial cells, endothelium) have been identified. In addition, many flavonoids display significant antioxidant/radical scavenging properties. There is substantial structural variation in these compounds, which is bound to have an impact on their biological profile, and specifically on their effects on inflammatory conditions. However, in general terms there is substantial consistency in the effects of these compounds despite considerable structural variations. The mechanisms have been studied mainly in myeloid cells, where the predominant effect is an inhibition of NF-κB signaling and the downregulation of the expression of proinflammatory markers. At present there is a gap in knowledge of in vitro and in vivo effects, although the pharmacokinetics of flavonoids has advanced considerably in the last decade. Many flavonoids have been studied for their intestinal antiinflammatory activity which is only logical, since the gastrointestinal tract is naturally exposed to them. However, their potential therapeutic application in inflammation is not restricted to this organ and extends to other sites and conditions, including arthritis, asthma, encephalomyelitis, and atherosclerosis, among others.

Effects of Flavonoids and other Polyphenols on Inflammation

Many of the inflammatory diseases are becoming common in aging society throughout the world. The clinically used anti-inflammatory drugs suffer from the disadvantage of side effects and high cost of treatment (in case of biologics). Alternative to these drugs are traditional medicines and natural products, which offer a great hope in the identification of bioactive lead compounds and their development into drugs for treating inflammatory diseases. Since ancient times traditional medicines and phytopharmaceuticals are being used for the treatment of inflammatory and other disorders. The present review article describes anti-inflammatory natural products derived from plants and marine sources reported during last decade. The compounds described belong to different chemical classes such as alkaloids, steroids, terpenoids, polyphenolics, phenylpropanoids, fatty acids and lipids, and various miscellaneous compounds. The attempt is also being made to enumerate the possible leads, e.g. curcumin, resveratrol, baicalein, boswellic acid, betulinic acid, ursolic acid, and oleanolic acid, for further development with the help of structure–activity relationship (SAR) studies and their current status. In addition SAR studies carried out on the anti-inflammatory activity of flavonoid compounds and clinical studies performed on anti-inflammatory natural products are also discussed. © 2009 Wiley Periodicals, Inc. Med Res Rev, 29, No. 5, 767–820, 2009

Recent developments in anti-inflammatory natural products.

The amount of research activity concerning alpha-methylene-gamma-butyrolactones and alpha-alkylidene-gamma-butyrolactones has increased dramatically in recent years. This Review summarizes the structural types, biological activities, and biosynthesis of these compounds, concentrating on publications from the past 10 years. Traditional approaches to alpha-methylene-gamma-butyrolactones and alpha-alkylidene-gamma-butyrolactones are then reviewed together with novel approaches, including those from our own research group, reported more recently.

The Renaissance of α‐Methylene‐γ‐butyrolactones: New Synthetic Approaches

Isolation and analysis of ginseng: advances and challenges

Inflammation has been reported to be intimately linked to the development or worsening of several non-infectious diseases. A number of chronic conditions such as cancer, diabetes, cardiovascular disorders, autoimmune diseases, and neurodegenerative disorders emerge as a result of tissue injury and genomic changes induced by constant low-grade inflammation in and around the affected tissue or organ. The existing therapies for most of these chronic conditions sometimes leave more debilitating effects than the disease itself, warranting the advent of safer, less toxic, and more cost-effective therapeutic alternatives for the patients. For centuries, flavonoids and their preparations have been used to treat various human illnesses, and their continual use has persevered throughout the ages. This review focuses on the anti-inflammatory actions of flavonoids against chronic illnesses such as cancer, diabetes, cardiovascular diseases, and neuroinflammation with a special focus on apigenin, a relatively less toxic and non-mutagenic flavonoid with remarkable pharmacodynamics. Additionally, inflammation in the central nervous system (CNS) due to diseases such as multiple sclerosis (MS) gives ready access to circulating lymphocytes, monocytes/macrophages, and dendritic cells (DCs), causing edema, further inflammation, and demyelination. As the dearth of safe anti-inflammatory therapies is dire in the case of CNS-related disorders, we reviewed the neuroprotective actions of apigenin and other flavonoids. Existing epidemiological and pre-clinical studies present considerable evidence in favor of developing apigenin as a natural alternative therapy against chronic inflammatory conditions.

Potential Role of Flavonoids in Treating Chronic Inflammatory Diseases with a Special Focus on the Anti-Inflammatory Activity of Apigenin.

Apigenin inhibits the production of NO and PGE2 in microglia and inhibits neuronal cell death in a middle cerebral artery occlusion-induced focal ischemia mice model

Spirobacillenes A and B, unusual spiro-cyclopentenones from Lysinibacillus fusiformis KMC003.

Aster scaber T. (Asteraceae) has been used to treat bruises, snakebite, headache, and dizziness in traditional Chinese medicine. In the present study, the neuroprotective effect of four quinic acid derivatives from A. scaber on amyloid Abeta-induced PC12 cell toxicity was investigated. When cells were treated with quinic acid derivatives prior to Abeta, cell toxicity was significantly diminished. Among quinic acid derivatives, (-)4,5-dicaffeoyl quinic acid (1) gave the highest protection against Abeta-induced cell toxicity. In addition, the neurotrophic effects of compounds were evaluated by microscopically monitoring their potency to induce neurite outgrowth in PC12 cells. Four quinic acid derivatives from A. scaber promoted neurite outgrowth in PC12 cells. Interestingly, a novel quinic acid, (-)3,5-dicaffeoyl-muco-quinic acid (2) was more effective than the other compounds in promoting neurite outgrowth. Unlike nerve growth factor, the withdrawal of quinic acids did not result in any significant decrease in cell viability. The results suggest that quinic acid derivatives from A. scaber might potentially be used as a therapeutic agent in Alzheimer disease.

Neuroprotective and Neurotrophic Effects of Quinic Acids from Aster scaber in PC12 Cells

Two new polyacetylenes, oploxynes A (1) and B (2), and the known oplopandiol (3) and falcarindiol (4) were isolated from the stem of Oplopanax elatus. The structures of compounds 1 and 2 were determined to be 9,10-epoxyheptadeca-4,6-diyne-3,8-diol and 10-methoxyheptadeca-4,6-diyne-3,8,9-triol, respectively, on the basis of their UV, MS, and NMR data. The absolute configurations of these compounds were determined using the modified Mosher’s method and acetonide formation. Oploxyne A (1), oplopandiol (3), and falcarindiol (4) inhibited the formation of nitric oxide (NO) and prostaglandin E2 (PGE2) in lipopolysaccharide (LPS)-induced murine macrophage RAW 267.7 cells.

Oploxynes A and B, polyacetylenes from the stems of Oplopanax elatus.

A new diketopiperazine, glionitrin B (1), was produced using a microbial coculture of the fungus Aspergillus fumigatus KMC-901 and the bacterium Sphingomonas sp. KMK-001 that were isolated from acidic coal mine drainage. The structure of 1 was determined to be (3S,10aS)-dithiomethylglionitrin A. This structure was determined by the analyses of extensive NMR data and the circular dichroism spectra of the natural product and a semisynthetic compound derived from glionitrin A. In contrast to glionitrin A (2), glionitrin B (1) is not cytotoxic against the human prostate cancer cell line DU145. However, compound 1 caused suppression of DU145 cell invasion, producing 46% inhibition at 60 μM.

Kang Ro Lee

Papers

Apigenin inhibits the production of NO and PGE2 in microglia and inhibits neuronal cell death in a middle cerebral artery occlusion-induced focal ischemia mice model

Spirobacillenes A and B, unusual spiro-cyclopentenones from Lysinibacillus fusiformis KMC003.

Neuroprotective and Neurotrophic Effects of Quinic Acids from Aster scaber in PC12 Cells

Oploxynes A and B, polyacetylenes from the stems of Oplopanax elatus.

Glionitrin B, a cancer invasion inhibitory diketopiperazine produced by microbial coculture.