ABSTRACT
Sea cucumber saponins (SCSs) exhibit a wide spectrum of bioactivities, but their metabolic characteristics are not well elucidated. In this study, the metabolism of holothurin A (HA) and echinoside A (EA), 2 major saponins in sea cucumber, by gut microflora were investigated. First, we conducted an in vitro study, where in the SCSs were incubated with intestinal microflora and the metabolites were detected by high pressure liquid chromatography-high resolution mass spectrometry. We also conducted an in vivo study on rats, where in the intestinal contents, serum, urine, and feces were collected and evaluated after oral administration of SCSs. In the in vitro study, we identified 6 deglycosylated metabolites of HA and EA, assigned M1-M6. In the in vivo study, we found all the deglycosylated metabolites in the intestinal contents after oral administration, and both the metabolites and their prototype components could be absorbed. Four metabolites were identified in the serum, 6 in the urine, and 4 in the feces. The saponins with different structures showed different absorption characteristics in rats. According to our results, deglycosylation is the main intestinal microflora-mediated metabolic pathway for SCSs, and both the SCSs and deglycosylated metabolites can be absorbed by intestine. This study improves the understanding of the metabolism of HA and EA by gut flora, which will be useful for further analysis of the bioactivity mechanism of SCSs.
Subject(s)
Holothurin/analogs & derivatives , Sea Cucumbers/metabolism , Animals , Chromatography, High Pressure Liquid/methods , Feces/chemistry , Gastrointestinal Microbiome , Holothurin/chemistry , Holothurin/metabolism , Intestinal Mucosa/metabolism , Intestines/microbiology , Male , Mass Spectrometry/methods , Metabolic Networks and Pathways , Rats , Saponins/analysis , Sea Cucumbers/chemistryABSTRACT
The present study is focused on the intestinal absorption of sea cucumber saponins. We determined the pharmacokinetic characteristics and bioavailability of Echinoside A and Holotoxin A1; the findings indicated that the bioavailability of Holotoxin A1 was lower than Echinoside A. We inferred that the differences in chemical structure between compounds was a factor that explained their different characteristics of transport across the intestine. In order to confirm the absorption characteristics of Echinoside A and Holotoxin A1, we examined their transport across Caco-2 cell monolayer and effective permeability by single-pass intestinal perfusion. The results of Caco-2 cell model indicate that Echinoside A is transported by passive diffusion, and not influenced by the exocytosis of P-glycoprotein (P-gp, expressed in the apical side of Caco-2 monolayers as the classic inhibitor). The intestinal perfusion also demonstrated well the absorption of Echinoside A and poor absorption of Holotoxin A1, which matched up with the result of the Caco-2 cell model. The results demonstrated our conjecture and provides fundamental information on the relationship between the chemical structure of these sea cucumber saponins and their absorption characteristics, and we believe that our findings build a foundation for the further metabolism study of sea cucumber saponins and contribute to the further clinical research of saponins.
Subject(s)
Intestinal Absorption/physiology , Saponins/metabolism , Sea Cucumbers/metabolism , Stichopus/metabolism , Animals , Biological Availability , Biological Transport/physiology , Caco-2 Cells , Cell Line, Tumor , Glycosides/metabolism , Holothurin/analogs & derivatives , Holothurin/metabolism , Humans , Intestinal Mucosa/metabolism , Male , Rats , Rats, Wistar , Saponins/pharmacokinetics , Triterpenes/metabolismABSTRACT
Two similarly sulfated triterpene saponins from Pearsonothuria graeffei were prepared to investigate the anti-obesity effects of echinoside A (EA) and holothurin A (HA). The in vitro inhibitory activities of EA and HA toward pancreatic lipase were investigated, and two in vivo studies were performed: (i) Male Wistar rats were orally administered the lipid emulsion with or without a saponin (HA or EA). The serum's total triglyceride concentration was measured at various times. (ii) C57BL/6 mice were assigned to four groups, high fat (HF), EA (0.03%), HA (0.04%), and orlistat (0.01%), and the weight of adipose tissue and level of fatty acids excreted in the feces were determined. Both EA and HA repressed the pancreatic lipase activity and increased fatty acid excretion in the feces. Treatment with EA and HA significantly decreased the adipose tissue accumulation in mice. EA and HA manifested different inhibitory activities in vitro, but each of them dramatically inhibited lipid absorption in vivo and showed strong anti-obesity activity.
Subject(s)
Absorption, Physicochemical/drug effects , Dietary Fats/metabolism , Holothurin/analogs & derivatives , Obesity/drug therapy , Animals , Body Weight/drug effects , Eating/drug effects , Holothurin/chemistry , Holothurin/metabolism , Holothurin/pharmacology , Holothurin/therapeutic use , Lipase/antagonists & inhibitors , Lipase/chemistry , Lipase/metabolism , Liver/drug effects , Liver/pathology , Male , Mice , Molecular Docking Simulation , Obesity/metabolism , Obesity/pathology , Organ Size/drug effects , Pancreas/enzymology , Protein Conformation , RatsABSTRACT
Interaction between holothurin A triterpene glycoside and lipid-cholesterol liposomes was studied by differential scanning microcalorimetry. Partial restoration of the peak of basic phase transition of dipalmitoyl phosphatidyl choline was shown to be related to the formation of holothurin A (in the membrane)-cholesterol complex. The data obtained are in favor of "sterol" hypothesis of the mechanism of membrane-tropic action of holothurin A.
