Absorption characteristics of the total alkaloids from Mahonia bealei in an in situ single-pass intestinal perfusion assay

Recent Analytical Approaches for the Study of Bioavailability and Metabolism of Bioactive Phenolic Compounds

The study of the bioavailability of bioactive compounds is a fundamental step for the development of applications based on them, such as nutraceuticals, functional foods or cosmeceuticals. It is well-known that these compounds can undergo metabolic reactions before reaching therapeutic targets, which may also affect their bioactivity and possible applications. All recent studies that have focused on bioavailability and metabolism of phenolic and terpenoid compounds have been developed because of the advances in analytical chemistry and metabolomics approaches. The purpose of this review is to show the role of analytical chemistry and metabolomics in this field of knowledge. In this context, the different steps of the analytical chemistry workflow (design study, sample treatment, analytical techniques and data processing) applied in bioavailability and metabolism in vivo studies are detailed, as well as the most relevant results obtained from them.

Paeonol-loaded PLGA nanoparticles as an oral drug delivery system: Design, optimization and evaluation

Herein, we report a novel type of NPs by loading paeonol (Pae) into PLGA NPs, to enhance drug stability and oral bioavailability. The paeonol (Pae)-loaded polylactic-co-Gly-colic acid (PLGA) nanoparticles (Pae-PLGA-NPs) were prepared by nanoprecipitation method. The resultant NPs were in spherical shape with an average particle size around 237.7 ± 4.92 nm, and the PDI and zeta potential were 0.110 ± 0.01 and -25.33 ± 1.37 mV, respectively. The encapsulation efficiency (EE) and drug loading (DL) of the Pae-PLGA-NPs were 86.26 ± 1.12 and 12.74 ± 0.37% respectively. The in vitro drug release, in vivo pharmacokinetics and in situ single-pass intestinal perfusion (SPIPs) of Pae-PLGA-NPs was investigated. In vivo, the AUC_(0-t), C _max, MRT_(0-t), and T_1/2z of the Pae-PLGA-NPs group were 3.79-, 1.89-, 1.40- and 1.49-fold greater than those of the Pae suspension group, respectively. The in situ single-pass intestinal perfusion of NPs results showed the Ka values in the duodenum, jejunum, ileum and colon were 1.12-, 1.40-, 1.52- and 2.21-fold higher than those of Pae solution, respectively. Moreover, the Papp values of the ileum and colon were 1.27- and 1.31-fold higher than those of the solution group. Such findings suggested the Pae-PLGA-NPs can significantly improve the intestinal absorption characteristics, and have a beneficial effect on oral administration as a nanometer-sized carrier.

Exploring the compatibility mechanism of ShengDiHuang Decoction based on the in situ single-pass intestinal perfusion model

Affecting the absorption of active ingredients in the intestine serves as one of the important compatibility mechanisms of traditional Chinese medicine. The aim of this study was to investigate the compatibility mechanism of ShengDiHuang Decoction (SDHD) by using the single-pass intestinal perfusion in situ model. The major effective ingredients, catalpol, aucubin, acteoside, rehmannioside D, rehmannioside A, rhein, aloe emodin, emodin, chrysophanol, and physcion, were determined by HPLC. By analysing the effects of different concentrations, different pH, intestinal segments, protein inhibitors, and tight junction regulators on SDHD absorption, it was found that catalpol, aucubin, rehmannioside D, rehmannioside A, acteoside, rhein, and chrysophanol may undergo active transport, while aloe-emodin and emodin may undergo passive transport. Catalpol, aucubin, and rehmannioside D may be substrates of BCRP and MRP2, while rehmannioside A and rhein may be substrates of BCRP, and acteoside and chrysophanol may be substrates of P-gp, BCRP and MRP2. By comparing the P_app values of the major effective ingredients between single herb and herb-pairs, the compatibility of rehmannia and rheum could significantly promote the absorption of components in rehmannia. It is verified that rheum has a synergistic effect on the absorption of rehmannia in SDHD.

Different structures of berberine and five other protoberberine alkaloids that affect P-glycoprotein-mediated efflux capacity

Berberine, berberrubine, thalifendine, demethyleneberberine, jatrorrhizine, and columbamine are six natural protoberberine alkaloid (PA) compounds that display extensive pharmacological properties and share the same protoberberine molecular skeleton with only slight substitution differences. The oral delivery of most PAs is hindered by their poor bioavailability, which is largely caused by P-glycoprotein (P-gp)-mediated drug efflux. Meanwhile, P-gp undergoes large-scale conformational changes (from an inward-facing to an outward-facing state) when transporting substrates, and these changes might strongly affect the P-gp-binding specificity. To confirm whether these six compounds are substrates of P-gp, to investigate the differences in efflux capacity caused by their trivial structural differences and to reveal the key to increasing their binding affinity to P-gp, we conducted a series of in vivo, in vitro, and in silico assays. Here, we first confirmed that all six compounds were substrates of P-gp by comparing the drug concentrations in wild-type and P-gp-knockout mice in vivo. The efflux capacity (net efflux) ranked as berberrubine > berberine > columbamine ~ jatrorrhizine > thalifendine > demethyleneberberine based on in vitro transport studies in Caco-2 monolayers. Using molecular dynamics simulation and molecular docking techniques, we determined the transport pathways of the six compounds and their binding affinities to P-gp. The results suggested that at the early binding stage, different hydrophobic and electrostatic interactions collectively differentiate the binding affinities of the compounds to P-gp, whereas electrostatic interactions are the main determinant at the late release stage. In addition to hydrophobic interactions, hydrogen bonds play an important role in discriminating the binding affinities.

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).

San-Huang-Xie-Xin-Tang Constituents Exert Drug-Drug Interaction of Mutual Reinforcement at Both Pharmacodynamics and Pharmacokinetic Level: A Review

Inflammatory disorders underlie varieties of human diseases. San-Huang-Xie-xin-Tang (SHXXT), composed with Rhizoma Rhei (Rheum palmatum L.), Rhizoma Coptidis (Coptis chinensis Franch), and Radix Scutellaria (Scutellaria baicalensis Georgi), is a famous formula which has been widely used in the fight against inflammatory abnormalities. Mutual reinforcement is one of the basic theories of traditional Chinese medicine. Here this article reviewed and analyzed the recent research on (1) How the main constituents of SHXXT impact on inflammation-associated signaling pathway molecules. (2) The interaction between the main constituents and efflux pumps or intestinal transporters. The goal of this work was to, (1) Provide evidence to support the theory of mutual reinforcement. (2) Clarify the key targets of SHXXT and suggest which targets need further investigation. (3) Give advice for the clinical use of SHXXT to elevated the absorption of main constituents and eventually promote oral bioavailability. We search literatures in scientific databases with key words of “each main SHXXT constituent,” in combination with “each main inflammatory pathway target molecule” or each main intestinal transporter, respectively. We report the effect of five main constituents on target molecules which lies in three main inflammatory signaling pathways, we as well investigate the interaction between constituents and intestinal transporter. We conclude, (1) The synergistic effect of constituents at both levels confirm the mutual reinforcement theory of TCM as it is proven in this work. (2) The effect of main constituents on downstream targets in nuclear need more further investigation. (3) Drug elevating the absorption of rhein, berberine and baicalein can be employed to promote oral bioavailability of SHXXT.