Assessment of Intestinal Absorption of Vitexin-2″-O-Rhamnoside in Hawthorn Leaves Flavonoids in Rat Using In Situ and In Vitro Absorption Models

Gastrointestinal absorption and its regulation of hawthorn leaves flavonoids

Hawthorn leave flavonoids (HLF) are widely used as an herb or dietary supplements for cardio-cerebrovascular diseases. However, its gastrointestinal absorption behavior and mechanism have not been disclosed. In this study, gastrointestinal absorption and its regulation of 4''-O-glucosylvitexin (GLV), 2''-O-rhamnosylvitexin (RHV), vitexin (VIT), rutin (RUT) and hyperoside (HP) in HLF were investigated using in vitro, in situ and in vivo models. Apparent permeability coefficient (Papp) of five flavonoids were (2.18 ± 0.15) ×10-7~(3.83 ± 0.22) ×10-7 cm·sec-1 across the Caco-2 cells. GLV, RHV, VIT and RUT demonstrated similar and poor absorption in rat stomach (absorption percentage per hour (A), (1.78 ± 0.14 ~ 5.69 ± 0.51)%·h-1) and small intestine (absorption rate ([Formula: see text], (0.012 ± 0.006 ~ 0.055 ± 0.003) h-1), extent (A, (1.28 ± 0.14 ~ 2.82 ± 0.19)% ·h-1) and potential (Papp, (0.31 ± 0.05 ~ 1.41 ± 0.08)×10-7 cm·sec-1)), while HP showed relatively better absorption (Papp, (2.55 ± 0.15 ~ 4.27 ± 0.36)×10-7 cm·sec-1) in rat small intestine. Absorption of five flavonoids exhibited dose-dependence, pH-dependence and region-selectivity. Meanwhile, these flavonoids were excreted via intestine, secreted via bile and metabolized by intestinal microflora. Their absorption was significantly increased by absorption enhancers (cow bile salt and sodium dodecyl sulphate), transporter regulators (verapamil hydrochloride, digoxin and rifampicin). GLV and RHV exhibited enterohepatic circulation after oral administration of HLF. In conclusion, flavonoids in HLF were absorbed via passive diffusion accompanied with active transport, intestinal microflora metabolism, bile secretion and intestinal efflux. They belong to BCS class III ("like" drugs with high solubility and low permeability) and displayed poor oral bioavailability.

Preclinical models for colonic absorption, application to controlled release formulation development

Oral controlled release (CR) formulations have many benefits and have become a valuable resource for the local and systemic administration of drugs. The most important characteristic of these pharmaceutical products is that drug absorption occurs mainly in the colon. Therefore, this review analyses the physiological and physicochemical features that may affect an orally administered CR product, as well as the different strategies to develop a CR dosage form and the methods used to evaluate the formulation efficacy. The models available to study the intestinal permeability and their applicability to colonic permeability determinations are also discussed.

Study of Absorption Characteristics of the Total Saponins from Radix Ilicis Pubescentis in an In Situ Single-Pass Intestinal Perfusion (SPIP) Rat Model by Using Ultra Performance Liquid Chromatography (UPLC)

In contrast to the extensively reported therapeutic activities, far less attention has been paid to the intestinal absorption of the total saponins from Radix Ilicis Pubescentis (in Chinese Mao-Dong-Qing, MDQ). This study aimed to investigate the intestinal absorption characteristics of ilexgenin A (C1), ilexsaponin A1 (C2), ilexsaponin B1 (C3), ilexsaponin B2 (C4), ilexsaponin B3 (DC1), and ilexoside O (DC2) when administrated with the total saponins from MDQ (MDQ-TS). An UPLC method for simultaneous determination of C1, C2, C3, C4, DC1, and DC2 in intestinal outflow perfusate was developed and validated. The absorption characteristics of MDQ-TS were investigated by evaluating the effects of intestinal segments, drug concentration, P-glycoprotein (P-gp) inhibitor (verapomil), endocytosis inhibitor (amantadine) and ethylene diamine tetraacetic acid (EDTA, tight junction modulator) on the intestinal transportation of MDQ-TS by using a single-pass intestinal perfusion (SPIP) rat model, and the influence of co-existing components on the intestinal transport of the six saponins was discussed. The results showed that effective apparent permeability (P_app) of C1, C2, C3, C4, and DC2 administrated in MDQ-TS form had no segment-dependent changes at low and middle dosage levels. C1, C2, C3, D4, DC1, and DC2 administrated in MDQ-TS form all exhibited excellent transmembrane permeability with P_app > 0.12 × 10⁻² cm·min⁻¹. Meanwhile, P_app and effective absorption rate constant (K_a) values for the most saponins showed concentration dependence and saturation characteristics. After combining with P-gp inhibitor of verapamil, P_app of C2, C3, and DC1 in MDQ-TS group was significantly increased up to about 2.3-fold, 1.4-fold, and 3.4-fold, respectively in comparison to that of non-verapamil added group. Verapamil was found to improve the absorption of C2, C3, and DC1, indicating the involvement of an active transport mechanism in the absorption process. Compared with the non-amantadine added group, the absorption of C1, C2, C4, DC1, and DC2 were decreased by 40%, 71%, 31%, 53%, and 100%, respectively. P_app for the six target compounds increased up to about 1.2–2.1-fold in comparison with the non-EDTA added, respectively. The gastrointestinal transport of MDQ-TS could be greatly promoted by EDTA, and inhibited by amantadine, implying that the intestinal absorption of MDQ-TS was by passive diffusion and endocytosis process. Compared with monomer administration group, the intestinal absorption of C3, C4, DC1, and DC2 was significantly improved by co-existing components in MDQ-TS, and the non-absorbable saponins of C4, DC1, and DC2 unexpectedly showed sufficient intestinal permeability with P_app > 0.12 × 10⁻² cm·min⁻¹. This suggested that compounds orally administrated in TCM extract forms displayed unique intestinal absorption characteristics different from those of monomers, and the enhancing intestinal absorption of MDQ-TS reflected a holistic and specific view of traditional Chinese medicines (TCMs).

WITHDRAWN: The paradox of natural flavonoid C-glycosides and health benefits: When more occurrence is less research

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Intestinal permeability of Lamivudine using single pass intestinal perfusion

The intestinal transport of lamivudine, a nucleotide reverse transcriptase inhibitor, was investigated using the single pass intestinal perfusion technique in male Wistar rats. Single pass intestinal perfusion was performed in small intestine at a flow rate of 0.20 ml/min. Lamivudine exhibits a high intestinal permeability over the length of the small intestine indicative of compounds that are well absorbed. The P_eff of lamivudine is in the range of drugs with high intestinal permeability and high fraction of dose absorbed indicating that lamivudine readily crosses the intestine. This also suggests that lamivudine belongs to biopharmaceutics classification system class I and is a good candidate for biopharmaceutics classification system based biowaiver. The permeability values obtained from this study may be useful in models of exposure assessment.

Everted gut sac model as a tool in pharmaceutical research: limitations and applications

OBJECTIVES

This review discusses the limitations and applications of the everted gut sac model in studying drug absorption, metabolism, and interaction.

KEY FINDINGS

The mechanism of drug absorption, interaction and the effect of factors such as age, sex, species, chronic therapy, and disease state on drug absorption have been summarized. The experimental conditions and their effects on the outcomes of trials have been discussed also.

SUMMARY

The everted sac model is an efficient tool for studying in-vitro drug absorption mechanisms, intestinal metabolism of drugs, role of transporter in drug absorption, and for investigating the role of intestinal enzymes during drug transport through the intestine.

The pharmacokinetics of C-glycosyl flavones of Hawthorn leaf flavonoids in rat after single dose oral administration

Hawthorn leaf flavonoids (HLF) are used in the treatment of cardiovascular diseases. Various potential pharmacodynamic effects have been observed for vitexin-4''-O-glucoside (VOG) and vitexin-2''-O-rhamnoside (VOR) which are the main constituents of HLF. The aim of this study was to investigate the pharmacokinetics of VOG and VOR when a single dose of HLF was administrated orally. The levels of VOG and VOR in plasma, tissues (heart, liver, spleen, lung, kidney and brain), bile, urine and feces were measured by HPLC-UV. The results showed that VOG and VOR have the similar pharmacokinetics. Both of them were absorbed quickly into plasma with maximal plasma concentrations of VOG and VOR being reached within 0.75 h. The mean elimination half-life (t(1/2)) of VOG and VOR were 2.53 h and 2.32 h, respectively. High levels of tissue distribution of VOG and VOR were observed in liver and kidney. No VOG and VOR were detected in brain tissue. There was no long-term accumulation of VOG and VOR in rat tissues examined. The total recovery of the dose in 24 hours was 64.91% (0.70% in urine; 64.21% in feces) for VOG and 89.01% (0.72% in urine; 88.29% in feces) for VOR. The cumulative VOG and VOR excreted in bile represented 0.58% and 13.38% of the doses, respectively. VOG and VOR in HLF were not efficiently absorbed in the rodent gastrointestinal tract.