| Citrus reticulate “chichi” peel is the mature peel of citrus reticulata. A genuinemedicinal material, the edible Chinese herbal mandarin orange peel is rooted in it.Our group has done several studies on it, including:1. The extraction process of ECRPwas optimized by using response surface methodology with antioxidant activity as the indicator.2.A series of in vitro antioxidant models and D-galactose-induced aging mice modelexperiments have suggested that the extract of Citrus reticulata ‘chachi’ peel(ECRP)possessed excellent antioxidant activity.3. The components of ECRP in plasma were mainlyidentified as PMFs based on the principle of serum medicinal chemistry.4. H2O2-induced PC12cell oxidative stress injury model was applied to evaluate the antioxidative effects of6PMFs.Nobiletin and tangeretin, as the highest content components of PMFs of ECRP,was identified as the antioxidative index ingredients of ECRP in this article. We haveinvestigated their antioxidant activity by a series of in vitro antioxidant experiments.In addition, blood drug concentration determination was utilized to study thepharmacokinetics of nobiletin and tangeretin in rat plasma after oral administration ofECRP. Moreover, we built in situ single pass perfusion model to investigate theabsorption in small intestine of nobiletin and tangeretin of ECRP, and influencefactors of absorption were studied as well.Integrated content and the results of this article, summarized as follows:1. In vitro antioxidant experiments of nobiletin and tangeretinDPPH assay, ABTS assay, FRAP assay and Fenton reaction were all used toinvestigate the antioxidative activities of nobiletin and tangeretin. The result of DPPHassay and ABTS assay suggested that nobiletin and tangeretin have expressed a certain ability of free radical scavenging. But they have weak reducibility and captureof radical according to the FRAP assay and Fenton reaction.2. Acute toxicity test of ECRPAfter oral administration of different dosage of ECRP, death, weight, behavior andexcretion of rats were observed. The results suggested that ECRP was nontoxic andreached toxicity criteria of health care products.3. Pharmacokinetic study of nobiletin and tangeretin in ECRPBio-sample pretreatment and HPLC method were built to determine rat plasmaconcentration of nobiletin and tangeretin after oral administration of ECRP.Pharmacokinetic parameters were assessed with noncompartment model by DAS2.0.Nobiletin:Tmax=3.10±2.70h，Cmax=4.62±0.84mg L-1，AUC0-t=46.67±20.26mg L-1·h，AUC0-∞=66.09±30.01mg L-1·h，t1/2=12.19±1.87h，CL/F=5.315±3.967L h-1kg-1；Tangeretin:Tmax=1.20±0.60h，Cmax=1.43±0.42mg L-1，AUC0-t=8.81±4.24mg L-1·h，AUC0-∞=9.73±4.67mg L-1·h，t1/2=7.66±0.81h，CL/F=26.37±12.54.4. Intestinal absorption study of nobiletin and tangeretin in ECRPIn situ single pass perfusion model and HPLC method were used to investigatenobiletin and tangeretin content in the solution before and after ECRP’s perfusion ofduodenum, jejunum, ileum and colon. Ingredients’ concentrations affected bymoisture loss and absorption, were revised by gravimetric method. The absorptionrate constant (Ka) and apparent absorption coefficient (Kapp), were calculated and usedto evaluate the absorption of nobiletin and tangeretin in small intestine. The resultsuggested that there are remarkable differences in absorption between nobiletin andtangeretin. Although these ingredients have the best absorption in the jejunum, thesame component in different intestine segments has no significant difference.5. Influence factors of absorption in duodenum of ECRPThe absorption rate constant (Ka) and apparent absorption coefficient (Kapp) ofnobiletin and tangeretin, were calculated after perfusion in duodenum by ECRPperfusates which were in different concentration and pH. These parameters were used to evaluate the influences of drug concentration and pH of absorption. The resultsuggested that, in test range, ECRP perfusates in different concentration and pHwould perform no significant differences in absorption in duodenum. |
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