Flavonoids are present in almost all terrestrial plants, where they provide UVprotection and colour. Flavonoids have a fused ring system consisting of an aromatic ring and a benzopyran ring with a phenyl substituent. The flavonoids can be divided into several classes depending on their structure. Flavonoids are present in food and medicinal plants and are thus consumed by humans. They are found in plants as glycosides. Before oral absorption, flavonoids undergo deglycosylation either by lactase phloridzin hydrolase or cytosolic β-glucocidase. The absorbed aglycone is then conjugated by methylation, sulphatation or glucuronidation. Both the aglycones and the conjugates can pass the bloodbrain barrier. In the CNS several flavones bind to the benzodiazepine site on the GABA Areceptor resulting in sedation, anxiolytic or anti-convulsive effects. Flavonoids of several classes are inhibitors of monoamine oxidase A or B, thereby working as anti-depressants or to improve the conditions of Parkinson's patients. Flavanols, flavanones and anthocyanidins have protective effects preventing inflammatory processes leading to nerve injury. Flavonoids seem capable of influencing health and mood.

Cell culture systems are widely used for the investigation of in vitro immunomodulatory effects of medicines and natural products. Since many pharmacological relevant compounds are water-insoluble, solvents are frequently used in cell based assays. Although many reports describe the cellular effects of solvents at high concentrations, only a few relate the effects of solvents used at low concentrations. In this report we investigate the interference of three commonly used solvents: Dimethyl sulfoxide (DMSO), ethanol and β-cyclodextrin with five different cell culture systems. The effects of the solvents are investigated in relation to the cellular production of interleukin (IL)-6 or reactive oxygen species (ROS) after lipopolysaccharide (LPS) stimulation. We show that DMSO above 1 % reduces readout parameters in all cell types but more interestingly the 0.25 and 0.5 % solutions induce inhibitory effects in some cell types and stimulatory effects in others. We also found that LPS induced ROS production was more affected than the IL-6 production in the presence of ethanol. Finally we showed that β-cyclodextrin at the investigated concentrations did not have any effect on the LPS induced IL-6 production and only minor effects on the ROS production. We conclude that the effects induced by solvents even at low concentrations are highly relevant for the interpretation of immunomodulatory effects evaluated in cell assays. Furthermore, these results show the importance of keeping solvent concentrations constant in serial dilution of any compound investigated in cell based assays.

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A previously published systematic review and a metaanalysis have concluded that the consumption of standardized rose hip powder (Rosa canina L.) can reduce pain in osteoarthritis patients. Synovial inflammation has been suggested to play an important role in the pathogenesis of osteoarthritis and mainly to involve infiltration of the synovial membrane by macrophages. Therefore, the immunomodulatory effect of standardized rose hip powder of Rosa canina L. was investigated and active principles isolated using the Mono Mac 6 cell line as a model for human macrophages. Treatment of Mono Mac 6 cells with the residue of a crude dichloromethane extract of rose hip powder significantly and concentration dependently inhibited the lipopolysaccharide induced interleukin‐6 release. Through bioassay‐guided fractionation the immunomodulatory effect of the dichloromethane extract was correlated to a mixture of three triterpene acids; oleanolic acid, betulinic acid and ursolic acid (IC50 21 ± 6 µm). Further studies revealed that only oleanolic acid and ursolic acid, but not betulinic acid, could inhibit the lipopolysaccharide induced interleukin‐6 release from Mono Mac 6 cells when tested separately. Combination of either oleanolic acid or ursolic acid with betulinic acid enhanced the immunomodulatory effect of the two triterpene acids. Copyright © 2010 John Wiley & Sons, Ltd.

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