Hops’ interaction with Haemin
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J Antimicrob Chemother. 2005 Jun;55(6):883-7. Epub 2005 Apr 11.
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In vitro antiplasmodial activity of prenylated chalcone derivatives of hops (Humulus lupulus) and their interaction with haemin.
Institut für Pharmazie (Pharmazeutische Biologie), Freie Universität Berlin, Königin-Luise-Str. 2-4, D-14195 Berlin, Germany.
OBJECTIVES: There is an urgent need to discover new antimalarials, due to the spread of chloroquine resistance and the limited number of available drugs. Chalcones are one of the classes of natural products that are known to possess antiplasmodial properties. Therefore, the in vitro antiplasmodial activity of the main hop chalcone xanthohumol and seven derivatives was evaluated. In addition, the influence of the compounds on glutathione (GSH)-dependent haemin degradation was analysed to determine its contribution to the antimalarial effect of chalcones. METHODS: In vitro antiplasmodial activity was evaluated against the chloroquine-sensitive strain poW and the multiresistant clone Dd2 using a [(3)H]hypoxanthine-incorporation assay. Inhibition of GSH-dependent haemin degradation was analysed by a multiwell plate assay at 11 microM. RESULTS: Of the eight compounds tested, four possessed activity with IC(50) values<25 microM against at least one of the two strains of Plasmodium falciparum. The main hop chalcone, xanthohumol, was most active with IC(50) values of 8.2+/-0.3 (poW) and 24.0 +/- 0.8 microM (Dd2). Three of these compounds were additionally active in the haemin-degradation assay. CONCLUSIONS: The results demonstrate for the first time the ability of chalcone derivatives to interfere with the haemin-degradation process of P. falciparum. This effect might contribute to their antiplasmodial activity. Nevertheless, as one compound showed inhibition of P. falciparum without being able to interact with GSH-dependent haemin degradation, other modes of action must add to the observed antiparasitic activity of hop chalcones.
PMID: 15824094 [PubMed – indexed for MEDLINE]
XN and Rat Intestinal Microbiota
Mol Nutr Food Res. 2005 Sep;49(9):868-73.
Xanthohumol does not affect the composition of rat intestinal microbiota.
Department of Gastrointestinal Microbiology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany.
Xanthohumol (XN), a prenylated chalcone, has been proposed to have beneficial effects on human health, including antimicrobial activity. To clarify whether the exposure to XN has an impact on the composition of the intestinal microbiota, 100 mg XN/kg body weight was given daily to rats for 4 wk. Diversity of the fecal microbial community was analyzed using PCR-DGGE. Although intact XN was detected in the feces of the rats at a concentration of up to 2.3 mg/g fecal dry weight, major shifts in the PCR-DGGE patterns in response to this flavonoid were not observed. The similarity index decreased slightly from 70 to 62% for the XN-treated rats and from 71 to 63% for the untreated animals. Thus, changes in the rat fecal microbiota observed in the course of the XN application are most likely due to intraindividual variability. However, the water content of the feces increased significantly during the XN treatment period.
PMID: 16092067 [PubMed – indexed for MEDLINE]
One Molecule (XN) is About to Change Your World (English & Korean) 