Isolation and structural characterization of dihydrobenzofuran congeners of licochalcone A

Mechanism of pruritus ani lotion combined with Huajiao-Gancao-Bingpian oil for pruritus ani treatment based on network pharmacology and molecular dynamics

Introduction

Pruritus ani lotion combined with a Chinese medicine formula named Huajiao (Pericarpium Zanthoxyli Bungeani)-Gancao (Radix Glycyrrhizae)-Bingpian (Borneol) is effective in treating pruritus ani.

Aim

To investigate the mechanism of traditional Chinese medicine (TCM) in pruritus ani via network pharmacology and molecular dynamics (MD).

Material and methods

The Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) was utilised to screen active ingredients and their corresponding targets. Genes associated with pruritus ani were collected through GeneCards. Protein-protein interaction (PPI) network between target genes of the active ingredients of this formula and genes associated with pruritus ani was established through the STRING database. A drug-active ingredient-gene interaction network was constructed using Cytoscape with the top 50 genes in affinity coefficients. Molecular docking and MD simulation analysis were performed.

Results

Epidermal growth factor receptor (EGFR) and Signal Transducer and Activator of Transcription 3 (STAT3) were core genes. Direct targeting of EGFR by the active ingredients (quercetin and luteolin) and direct targeting of STAT3 by the active ingredient (licochalcone A) may be key molecular mechanisms for the treatment of pruritus ani. Simulated trajectories of structural nuclear motion by MD also revealed that the binding of two pairs of molecules was relatively stable.

Conclusions

This study unravels potential targets, active ingredients, and mechanisms of pruritus ani lotion combined with Huajiao-Gancao-Bingpian oil in the treatment of pruritus ani, providing a reference for future treatment.

Advances in Aβ imaging probes: a comprehensive study of radiolabelled 1,3-diaryl-2-propen-1-ones for Alzheimer's disease: a review

Alzheimer's disease (AD) is a formidable neurodegenerative disorder characterized by cognitive decline, memory impairment and inability to perform everyday tasks. In the pursuit of innovative diagnostic and therapeutic strategies, the synthesis and application of radiolabelled compounds have garnered significant attention. This review delves into the synthesis and biological significance of radiolabelled 1,3-diaryl-2-propen-1-ones, commonly known as chalcones, as Aβ imaging probes for AD. These versatile chalcone derivatives have demonstrated noteworthy potential as radiotracers for visualizing Aβ imaging probes, which are hallmark pathologies of AD. This review encompasses an exploration of chalcone synthesis via diverse methodologies and their biological implications, both as standalone entities and as precursors for intricate natural products. In addition, the pivotal role of advanced imaging techniques, such as single-photon emission computed tomography (SPECT) and positron emission tomography (PET), using various radioisotopes is highlighted. The use of radiopharmaceutical agents, including [18F]FDG, [18F]FMAPO, [11C]6-Me-BTA-1, [124/125I]IBETA, and [64Cu]YW-7 as potent tools for early diagnosis and therapeutic advancement is explored. This review underscores the critical nexus between radiolabelled chalcones and their pivotal role in advancing diagnostic and therapeutic paradigms in AD research. Furthermore, this study encapsulated the role of radiolabelled chalcone emphasizing their prospective implications for drug development and therapeutic interventions. A focal point of paramount significance is the elucidation of Aβ imaging probes and its important role in the combat against AD, with a particular emphasis on their role in facilitating early diagnosis and fostering advancements in therapeutic strategies.

A combined experimental and computational chiroptical approach to establish the biosynthesis and absolute configuration of licochalcone L

Often, chiral natural products exist as single stereoisomers; however, simultaneous occurrences of both enantiomers can exist in nature, resulting in scalemic or racemic mixtures. Ascertaining natural products' absolute configuration (AC) is pivotal for attributing their specific biological signature. Specific rotation data commonly characterize chiral non-racemic natural products; however, measurement conditions, viz., solvent and concentration, can influence the sign of specific rotation values, especially when characterizing natural products possessing small specific rotation values. For example, licochalcone L, a minor constituent of Glycyrrhiza inflata, was reported with a specific rotation of [α]_D²²= +13 (c 0.1, CHCl₃); however, not establishing the AC and the reported zero specific rotation for an identical compound, licochalcone AF1, resulted in debatable chirality and its biogenesis. In this study, a combined experimental and computational chiroptical approach involving specific rotation and electronic circular dichroism (ECD) data, supported by time-dependent density functional theory (TDDFT), were effectively utilized to establish the AC of licochalcone L as the (E, 2″S)-isomer. Establishing the 2″S absolute configuration permitted the conception of a reasonable biosynthetic pathway involving intramolecular '5-exo-tet' ring opening of a chiral oxirane to form chiral licochalcone L in G. inflata.

Computational Tools to Expedite the Identification of Potential PXR Modulators in Complex Natural Product Mixtures: A Case Study with Five Closely Related Licorice Species

The genus Glycyrrhiza, comprising approximately 36 spp., possesses complex structural diversity and is documented to possess a wide spectrum of biological activities. Understanding and finding the mechanisms of efficacy or safety for a plant-based therapy is very challenging, yet it is crucial and necessary to understand the polypharmacology of traditional medicines. Licorice extract was shown to modulate the xenobiotic receptors, which might manifest as a potential route for natural product-induced drug interactions. However, different mechanisms could be involved in this phenomenon. Since the induced herb-drug interaction of licorice supplements via Pregnane X receptor (PXR) is understudied, we ventured out to analyze the potential modulators of PXR in complex mixtures such as whole extracts by applying computational mining tools. A total of 518 structures from five species of Glycyrrhiza: 183 (G. glabra), 180 (G. uralensis), 100 (G. inflata), 33 (G. echinata), and 22 (G. lepidota) were collected and post-processed to yield 387 unique compounds. Visual inspection of top candidates with favorable ligand-PXR interactions and the highest docking scores were identified. The in vitro testing revealed that glabridin (GG-14) is the most potent PXR activator among the tested compounds, followed by licoisoflavone A, licoisoflavanone, and glycycoumarin. A 200 ns molecular dynamics study with glabridin confirmed the stability of the glabridin-PXR complex, highlighting the importance of computational methods for rapid dereplication of potential xenobiotic modulators in a complex mixture instead of undertaking time-consuming classical biological testing of all compounds in a given botanical.

Role of Licochalcone A in Potential Pharmacological Therapy: A Review

Licochalcone A (LA), a useful and valuable flavonoid, is isolated from Glycyrrhiza uralensis Fisch. ex DC. and widely used clinically in traditional Chinese medicine. We systematically updated the latest information on the pharmacology of LA over the past decade from several authoritative internet databases, including Web of Science, Elsevier, Europe PMC, Wiley Online Library, and PubMed. A combination of keywords containing “Licochalcone A,” “Flavonoid,” and “Pharmacological Therapy” was used to help ensure a comprehensive review. Collected information demonstrates a wide range of pharmacological properties for LA, including anticancer, anti-inflammatory, antioxidant, antibacterial, anti-parasitic, bone protection, blood glucose and lipid regulation, neuroprotection, and skin protection. LA activity is mediated through several signaling pathways, such as PI3K/Akt/mTOR, P53, NF-κB, and P38. Caspase-3 apoptosis, MAPK inflammatory, and Nrf2 oxidative stress signaling pathways are also involved with multiple therapeutic targets, such as TNF-α, VEGF, Fas, FasL, PI3K, AKT, and caspases. Recent studies mainly focus on the anticancer properties of LA, which suggests that the pharmacology of other aspects of LA will need additional study. At the end of this review, current challenges and future research directions on LA are discussed. This review is divided into three parts based on the pharmacological effects of LA for the convenience of readers. We anticipate that this review will inspire further research.

Discovery and Photoisomerization of New Pyrrolosesquiterpenoids Glaciapyrroles D and E, from Deep-Sea Sediment Streptomyces sp

Two new pyrrolosesquiterpenes, glaciapyrroles D (1) and E (2) were discovered along with the previously reported glaciapyrrole A (3) from Streptomyces sp. GGS53 strain isolated from deep-sea sediment. This study elucidated the planar structures of 1 and 2 using nuclear magnetic resonance (NMR), mass spectrometry (MS), ultraviolet (UV), and infrared (IR) spectroscopic data. The absolute configurations of the glaciapyrroles were determined by Mosher’s method, circular dichroism spectroscopy, and X-ray crystallography. Under 366 nm UV irradiation, the glaciapyrroles were systematically converted to the corresponding photoglaciapyrroles (4–6) via photoisomerization, resulting in the diversification of the glaciapyrrole family compounds. The transformation of the glaciapyrrole Z to E isomers occurred in a 1:1 ratio, based on virtual validation of the photoisomerization of these olefinic compounds by ¹H-NMR spectroscopy and liquid chromatography/mass spectrometry (LC/MS) analysis. Finally, when encapsulated in poly(lactic-co-glycolic acid) nanoparticles, glaciapyrrole E and photoglaciapyrrole E displayed significant inhibitory activity against influenza A virus. This is the first report of antiviral effects from glaciapyrrole family compounds, whose biological functions have only been subjected to limited studies so far.

Synthesis and biological evaluation of halogenated phenoxychalcones and their corresponding pyrazolines as cytotoxic agents in human breast cancer

Novel halogenated phenoxychalcones 2a–f and their corresponding N-acetylpyrazolines 3a–f were synthesised and evaluated for their anticancer activities against breast cancer cell line (MCF-7) and normal breast cell line (MCF-10a), compared with staurosporine. All compounds showed moderate to good cytotoxic activity when compared to control. Compound 2c was the most active, with IC₅₀ = 1.52 µM and selectivity index = 15.24. Also, chalcone 2f showed significant cytotoxic activity with IC₅₀ = 1.87 µM and selectivity index = 11.03. Compound 2c decreased both total mitogen activated protein kinase (p38α MAPK) and phosphorylated enzyme in MCF-7 cells, suggesting its ability to decrease cell proliferation and survival. It also showed the ability to induce ROS in MCF-7 treated cells. Compound 2c exhibited apoptotic behaviour in MCF-7 cells due to cell accumulation in G2/M phase and elevation in late apoptosis 57.78-fold more than control. Docking studies showed that compounds 2c and 2f interact with p38alpha MAPK active sites.

Microbial Conjugation Studies of Licochalcones and Xanthohumol

Microbial conjugation studies of licochalcones (1-4) and xanthohumol (5) were performed by using the fungi Mucor hiemalis and Absidia coerulea. As a result, one new glucosylated metabolite was produced by M. hiemalis whereas four new and three known sulfated metabolites were obtained by transformation with A. coerulea. Chemical structures of all the metabolites were elucidated on the basis of 1D-, 2D-NMR and mass spectroscopic data analyses. These results could contribute to a better understanding of the metabolic fates of licochalcones and xanthohumol in mammalian systems. Although licochalcone A 4'-sulfate (7) showed less cytotoxic activity against human cancer cell lines compared to its substrate licochalcone A, its activity was fairly retained with the IC₅₀ values in the range of 27.35-43.07 μM.

Prenylated Coumaric Acids from Artemisia scoparia Beneficially Modulate Adipogenesis

Two new diprenylated coumaric acid isomers (1a and 1b) and two known congeners, capillartemisin A (2) and B (3), were isolated from Artemisia scoparia as bioactive markers using bioactivity-guided HPLC fractionation. Their structures were determined by spectroscopic means, including 1D and 2D NMR methods and LC-MS, with their purity assessed by 1D ¹H pure shift qNMR spectroscopic analysis. The bioactivity of compounds was evaluated by enhanced accumulation of lipids, as measured using Oil Red O staining, and by increased expression of several adipocyte marker genes, including adiponectin in 3T3-L1 adipocytes relative to untreated negative controls. Compared to the plant's 80% EtOH extract, these purified compounds showed significant but still weaker inhibition of TNFα-induced lipolysis in 3T3-L1 adipocytes. This suggests that additional bioactive substances are responsible for the multiple metabolically favorable effects on adipocytes observed with Artemisia scoparia extract.

Chalcone and its analogs: Therapeutic and diagnostic applications in Alzheimer's disease

Chalcone [(E)-1,3-diphenyl-2-propene-1-one], a small molecule with α, β unsaturated carbonyl group is a precursor or component of many natural flavonoids and isoflavonoids. It is one of the privileged structures in medicinal chemistry. It possesses a wide range of biological activities encouraging many medicinal chemists to study this scaffold for its usefulness to oncology, infectious diseases, virology and neurodegenerative diseases including Alzheimer's disease (AD). Small molecular size, convenient and cost-effective synthesis, and flexibility for modifications to modulate lipophilicity suitable for blood brain barrier (BBB) permeability make chalcones a preferred candidate for their therapeutic and diagnostic potential in AD. This review summarizes and highlights the importance of chalcone and its analogs as single target small therapeutic agents, multi-target directed ligands (MTDLs) as well as molecular imaging agents for AD. The information summarized here will guide many medicinal chemist and researchers involved in drug discovery to consider chalcone as a potential scaffold for the development of anti-AD agents including theranostics.

Microbial Transformation of Licochalcones

Microbial transformation of licochalcones B (1), C (2), D (3), and H (4) using the filamentous fungi Aspergillus niger and Mucor hiemalis was investigated. Fungal transformation of the licochalcones followed by chromatographic separations led to the isolation of ten new compounds 5–14, including one hydrogenated, three dihydroxylated, three expoxidized, and three glucosylated metabolites. Their structures were elucidated by combined analyses of UV, IR, MS, NMR, and CD spectroscopic data. Absolute configurations of the 2″,3″-diols in the three dihydroxylated metabolites were determined by ECD experiments according to the Snatzke’s method. The trans-cis isomerization was observed for the metabolites 7, 11, 13, and 14 as evidenced by the analysis of their ¹H-NMR spectra and HPLC chromatograms. This could be useful in better understanding of the trans-cis isomerization mechanism of retrochalcones. The fungal transformation described herein also provides an effective method to expand the structural diversity of retrochalcones for further biological studies.

Residual Complexity Does Impact Organic Chemistry and Drug Discovery: The Case of Rufomyazine and Rufomycin

Residual complexity (RC) involves the impact of subtle but critical structural and biological features on drug lead validation, including unexplained effects related to unidentified impurities. RC commonly plagues drug discovery efforts due to the inherent imperfections of chromatographic separation methods. The new diketopiperazine, rufomyazine (6), and the previously known antibiotic, rufomycin (7), represent a prototypical case of RC that (almost) resulted in the misassignment of biological activity. The case exemplifies that impurities well below the natural abundance of ¹³C (1.1%) can be highly relevant and calls for advanced analytical characterization of drug leads with extended molar dynamic ranges of >1:1,000 using qNMR and LC-MS. Isolated from an actinomycete strain, 6 was originally found to be active against Mycobacterium tuberculosis with a minimum inhibitory concentration (MIC) of 2 μg/mL and high selectivity. As a part of lead validation, the dipeptide was synthesized and surprisingly found to be inactive. The initially observed activity was eventually attributed to a very minor contamination (0.24% [m/m]) with a highly active cyclic peptide (MIC ∼ 0.02 μM), subsequently identified as an analogue of 7. This study illustrates the serious implications RC can exert on organic chemistry and drug discovery, and what efforts are vital to improve lead validation and efficiency, especially in NP-related drug discovery programs.

Hepatic metabolism of licochalcone A, a potential chemopreventive chalcone from licorice (Glycyrrhiza inflata), determined using liquid chromatography-tandem mass spectrometry

The metabolism of the chemoprevention agent licochalcone A, which is a chemopreventive chalcone found in abundance in the licorice species Glycyrrhiza inflata, was investigated using human liver microsomes and human hepatocytes combined with analysis using high performance liquid chromatography-mass spectrometry (LC-MS). Five oxygenated phase I metabolites of licochalcone A were formed by human liver microsomes, including a catechol on the A-ring, two intramolecular cyclization products following epoxidation of the exocyclic alkene at position 5 of the B-ring, and two dioxygenated products. Nine phase II monoglucuronides of licochalcone A and its oxygenated phase I metabolites were formed during incubation with human hepatocytes. These included (E)-licochalcone A-4-glucuronide, (E)-licochalcone A-4'-glucuronide, (Z)-licochalcone A-4-glucuronide, glucuronic acid conjugates of all of the monooxygenated phase I metabolites, and glucuronides of the licochalcone catechol after methylation by catechol-O-methyl transferase. In addition, human hepatocytes formed one sulfate conjugate and one glutathione conjugate of licochalcone A. The structures of all major metabolites were determined using a combination of accurate mass measurement, LC-tandem mass spectrometry, LC-UV, nuclear magnetic resonance, and comparison with standards. The cytochrome P450 enzymes and UDP-glucuronosyltransferases responsible for the formation of the major metabolites were identified. Based on in vitro hepatic clearance calculations, licochalcone A is predicted to be metabolized primarily by phase II conjugation reactions. Graphical abstract Phase I and II metabolism of licochalcone A from the licorice species Glycyrrhiza inflata by human liver microsomes and hepatocytes determined using LC-MS/MS, LC-UV and NMR.