Biotransformation of 18β-Glycyrrhetinic Acid by Human Intestinal Fungus Aspergillus niger RG13B1 and the Potential Anti-Inflammatory Mechanism of Its Metabolites

A multistep approach for exploring quality markers of Shengjiang Xiexin decoction by integrating plasma pharmacochemistry-pharmacokinetics-pharmacology

Shengjiang Xiexin decoction (SXD), a well-known traditional Chinese medicine (TCM), was used to alleviate delayed-onset diarrhea induced by the chemotherapeutic agent irinotecan (CPT-11). Our previous study showed that SXD regulated multidrug resistance-associated protein 2 (Mrp-2) to alter the pharmacokinetics of CPT-11 and its metabolites. However, the pharmacodynamic constituents and the related quality markers of SXD are unclear. In this study, ultra-high performance liquid chromatography coupled with quadrupole orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS) was utilized to identify the prototypes and metabolites in rat plasma after oral administration of SXD. The pharmacokinetic markers (PK markers) were screened through quantification and semiquantification of SXD-related xenobiotics in plasma using liquid chromatography-mass spectrometry (LC-MS) combined with statistical analysis. Computational molecular docking was performed to assess the potential binding ability of the PK markers with the target Mrp-2. The results were verified by evaluating the impact on Mrp-2 function using Caco-2 cells. The quality markers were chosen from these PK markers based on the binding affinities with Mrp-2, the specificity and the traceability. As a result, a total of 142 SXD-related exogenous components, including 77 prototypes and 65 metabolites, were detected in rat plasma. Among these, 83 xenobiotics were selected as PK markers due to their satisfactory pharmacokinetic behaviors. Based on the characteristics of quality markers, the prototype-based PK markers were considered the indices of quality control for SXD, including baicalin, baicalein, wogonoside, wogonin, liquiritigenin, isoliquiritigenin, norwogonin, oroxylin A, dihydrobaicalin, chrysin, glycyrrhizic acid, glycyrrhetinic acid, oroxylin A 7-O-glucuronide, liquiritin and isoliquiritin. This study provided an interesting strategy for screening the quality markers involved in the pharmacokinetics of SXD and its action target, which offered important information for the modernization of SXD and other TCM formulae.

Degradation profile of environmental pollutant 17β-estradiol by human intestinal fungus Aspergillus niger RG13B1 and characterization of genes involved in its degradation

Environmental hormones have attracted more attention because of their adverse impact on the health and ecological security of human. Biodegradation is still an efficient tactics to remove environmental hormones, but human intestinal microbes remain to be elucidated in the role of their degradation. In the present work, we intended to perform the in vitro experiment for investigating the degradation of 17β-estradiol, the main environmental estrogen, by human intestinal microflora Aspergillus niger RG13B1. Its degradation led to the production of eighteen metabolites characterized by 1H, 13C, and 2D NMR, and HRMS spectra, including nine new (1-9) and nine known metabolites (10-18). Based on their structures, the degradation pathway of 17β-estradiol mediated by A. niger RG13B1 involved hydroxylation, oxidation, methylation, acetylation, and dehydrogenation, especially infrequent lactylation, and the key degradation enzymes were found in the gene cluster of A. niger. In addition, we found that metabolite 12 interacted with amino acid residues Lys37, Gln39, Lys93, and Asn115 of NF-κB p65 to suppress expressions of inflammatory genes or proteins, exerting its anti-inflammatory effect. This study first illustrated the role of human gut microbe in 17β-estradiol degradation and provided new insights into its degradation mechanism by A. niger RG13B1.

Inhibition effect of 1-acetoxy-6α-(2-methylbutyryl)eriolanolide toward soluble epoxide hydrolase: Multispectral analysis, molecular dynamics simulation, biochemical, and in vitro cell-based studies

Soluble epoxide hydrolase (sEH) serves as a potential target in inflammation-related diseases. Based on the bioactivity-guided separation, a new sesquiterpenoid inulajaponoid A (1) was isolated from Inula japonica with a sEH inhibitory effect, together with five known compounds, such as 1-O-acetyl-6-O-isobutyrylbritannilactone (2), 6β-hydroxytomentosin (3), 1β,8β-dihydroxyeudesma-4(15),11(13)-dien-12,6α-olide (4), (4S,6S,7S,8R)-1-O-acetyl-6-O-(3-methylvaleryloxy)-britannilactone (5), and 1-acetoxy-6α-(2-methylbutyryl)eriolanolide (6). Among them, compounds 1 and 6 were assigned as mixed and uncompetitive inhibitors, respectively. The result of immunoprecipitation (IP)-MS demonstrated the specific binding of compound 6 to sEH in the complex system, which was further confirmed by the fluorescence-based binding assay showing its equilibrium dissociation constant (K_d = 2.43 μM). The detail molecular stimulation revealed the mechanism of action of compound 6 with sEH through the hydrogen bond of amino acid residue Gln384. Furthermore, this natural sEH inhibitor (6) could suppress the MAPK/NF-κB activation to regulate inflammatory mediators, such as NO, TNF-α, and IL-6, which confirmed the anti-inflammatory effect of inhibition of sEH by 6. These findings provided a useful insight to develop sEH inhibitors upon the sesquiterpenoids.