| The human gut microflora is an enormously complex, diverse, and vast microbial community. In its entirety, the microflora is estimated to contain 10-fold more cells than our own host cells. Gut microbiota has been recently considered as a "hidden organ" of the body and has the potential to have an impact on health nutrition, metabolism, immune system, disease, health and many other physiological functions. Gut microbiota has been recently considered very important in pathogenesis of diseases related to energy metabolism. However, it is also an unexplored field for drug metabolism in gut microflora, especially for those administrated through oral route, as drug metabolism by gut microflora might generate metabolites different from that by host organs.Therefore, to explore drug metabolism by intestinal microorganism and provide explanation forits pharmaceutical research, we focused on the intestinal bacterial metabolism of natural active substance,berberine that wildly used in clinicandPolygonum capitatum, a traditional Miao-nationality herbal medicine, as two objects in this study.1. Studies on pharmacokinetics in vivo of berberine in gut microfloraBerberine (BBR) is anisoquinoline alkaloid isolated from Coptis chinensis and has been orally used in clinic as an over-the-counter drug to treat diarrhea. Recently, the therapeutic effect of BBR on lipid- and glucose-related metabolic disorders has been recently confirmed in a large number of patients by independent clinical groups in and outside China. However, BBR, a kind of quaternary ammonium salt, is poor in water solubility and its oral bioavailability of less than 1%. It is difficult to explain the poor absorption of BBR but with good multi-target therapeutic effect in clinic.To elucidate the mechanism of absorption after oral administration of BBR, we studied on the pharmacokinetic of BBR and effect of gut microbiota on the therapeutic efficacy of BBR in them.Firstly, pseudo germ-free ratswere prepared to study on the pharmacokinetic of BBR. The results demonstrated that, after oral administration of BBR (200 mg/kg),the Cmax and AUC(o-t) value of BBR in pseudo germ-free rats was 9.74±4.92ng/ml and 11.45±4.24ng/ml,respectively, which was lower than these in normal rats, the Cmax (25.85±7.34ng/ml) and AUC(0-t)(75.83±5.60ng/ml) of normal rats were 2.65 and 6.89 folds more than these in pseudo germ-free rats.The results of fecal detection were showed that oral administration of antibiotics decreased the amount of intestine bacteria and thus led to the reduction of dhBBR, which is a BBR metabolite only created in intestine ecosystem, resulting in a higher level of BBR excreted. The results further demonstrate the intestinal bacteria involved in the transformation of BBR to dhBBR.Secondly, pseudo germ-free KK-Ay mice were prepared to study oneffect of gut microbiota on the therapeutic efficacy of BBR in them. After oral administration of BBR for 14 days, the glucose (Glu), triglyceride (TG) and cholesterol (CHO) levels were evaluated in pseudo germ-free KK-Ay mice, and therapeutic results were shown that a low level of BBR in blood reduced therapeutic efficacy. As compared with BBR’s efficacy in normal KK-Ay mice (with no exposure to antibiotics), treating KK-Ay mice orally with antibiotics before and during BBR treatment largely reduced the therapeutic efficacy of BBR on fasting blood glucose by 22%, triglyceride by 53% and cholesterol by 44%, respectively. Therefore, intestinal flora can affect the transformation of BBR to its easier absorption form---dhBBR, since dhBBR was genarated via nitroreductase in gut microflora, this rate-limiting enzyme influenced the generation amount of dhBBR, thus limiting the absorption of BBR in gut. Lower conversion of dhBBR was reducing the BBR’s lipid-and glucose-lowering efficacy. Above all, we studied on pharmacokinetic of BBR in vivo, the dynamics of plasma and excretion of BBR, and also to participate in the regulation of therapeutic efficacy of BBR, and confirmed the intestinal flora can affect theconversion of BBR into dhBBR, which may be an important absorption mechanism of BBR in the gut.2. Studies on metabolismof active ingredients and extracts of Polygonum capitatum in gut microfloraPolygonum capitatum Buch.-Ham.ex D. Don has been widely used in the treatment of various urologic disorders. Recent pharmacological studies demonstrated that a pure compound, FR429, isolated from the ethanol extracts of P. capitatum could selectively inhibit the growth of four hepatocellular carcinoma (HCC) cell lines in a dose-dependent manner. Thus, P. capitatum probably exhibits potential antitumor activity. However, there is very little information on the metabolism of substances present in P. capitatum extracts. In this study, gallic acid, quercetrin, ethanol extracts and ethyl acetate fraction of ethnolic extract (EtOAc fraction) of P. capitatum were cultured anaerobically with rat intestinal bacteria. A highly sensitive and selective liquid chromatography electrospray ionization-ion trap-time of fight mass spectrometry (LC/MS-IT-TOF) technique was employed to identify and characterize the resulting metabolites. A total of 22 metabolites (M1-M22), including tannins, phenolic acids and flavonoids, were detected and characterized. The overall results demonstrated that theintestinal bacteria played an important role in the metabolism of P. capitatum, and the main metabolic pathways were hydrolysis, reduction and oxidation reactions.In summary, the interaction(s) between gut microbiota and chemical drugs giving through oral route might modify structure and function of the medicinal compounds and be important in drug investigation. The present study provided a paradigm for functional connections between gut microbiota and drug pharmacology, meanwhile, the result might enrich our understanding and knowledge for drug metabolism in vivo, mode of action, as well as druggability prediction. |
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