Identification of sinensetin metabolites in rat urine by an isotope-labeling method and ultrahigh-performance liquid chromatography-electrospray ionization mass spectrometry

Combination of in silico prediction and convolutional neural network framework for targeted screening of metabolites from LC-HRMS fingerprints: A case study of "Pericarpium Citri Reticulatae - FructusAurantii"

In this study, a novel approach is introduced, merging in silico prediction with a Convolutional Neural Network (CNN) framework for the targeted screening of in vivo metabolites in Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) fingerprints. Initially, three predictive tools, supplemented by literature, identify potential metabolites for target prototypes derived from Traditional Chinese Medicines (TCMs) or functional foods. Subsequently, a CNN is developed to minimize false positives from CWT-based peak detection. The Extracted Ion Chromatogram (EIC) peaks are then annotated using MS-FINDER across three levels of confidence. This methodology focuses on analyzing the metabolic fingerprints of rats administered with "Pericarpium Citri Reticulatae - Fructus Aurantii" (PCR-FA). Consequently, 384 peaks in positive mode and 282 in negative mode were identified as true peaks of probable metabolites. By contrasting these with "blank serum" data, EIC peaks of adequate intensity were chosen for MS/MS fragment analysis. Ultimately, 14 prototypes (including flavonoids and lactones) and 40 metabolites were precisely linked to their corresponding EIC peaks, thereby providing deeper insight into the pharmacological mechanism. This innovative strategy markedly enhances the chemical coverage in the targeted screening of LC-HRMS metabolic fingerprints.

Synthetic Studies toward 5,6,7,3',4'-Monomethoxytetrahydroxyflavones: Synthesis of Pedalitin

During the synthetic studies toward 5,6,7,3',4'-monomethoxytetrahydroxyflavones, a concise pedalitin synthesis procedure was achieved. As previously reported, 6-hydroxy-2,3,4-trimethoxyacetophenone was prepared by Friedel-Crafts acylation of 1,4-dihydroxy-2,6-dimethoxybenzene with boron trifluoride diethyl etherate in acetic acid. When aldol condensation of 6-hydroxy-2,3,4-trimethoxyacetophenone 2b with vanillin was performed in basic conditions, it produced 2'-hydroxychalcone 3b, and, surprisingly, along with 3-hydroxyflavone 4 in a considerable amount. We propose that this oxidative cyclization is presumably due to the contribution of a quinone methide, likely to be subjected to aerobic oxidation. The chalcone was then subjected to oxidative cyclization with iodine in dimethyl sulfoxide to afford flavone 5 in good yield. To our delight, serial demethylation of the three methoxy groups at the 5-, 6-, and 3'-positions of 5 proceeded smoothly to produce pedalitin 1, under hydrogen bromide solution (30% in acetic acid). The crystal structures of 3-hydroxyflavone 4 and pedalitin tetraacetate 6 were unambiguously determined by X-ray crystallography.

Seven-day Oral Intake of Orthosiphon stamineus Leaves Infusion Exerts Antiadhesive Ex Vivo Activity Against Uropathogenic E. coli in Urine Samples

Orthosiphon stamineus leaves (Java tea) extract is traditionally used for the treatment of urinary tract infections. According to recent in vitro data, animal infection studies, and transcriptomic investigations, polymethoxylated flavones from Java tea exert antiadhesive activity against uropathogenic Escherichia coli (UPEC). This antiadhesive activity has been shown to reduce bladder and kidney lesion in a mice infection model. As no data on the antivirulent activity of Java tea intake on humans are available, a biomedical study was performed on 20 healthy volunteers who self-administered Orthosiphon infusion (4 × 3 g per day, orally) for 7 days. The herbal material used for the study conformed to the specification of the European Pharmacopoeia, and ultra high-performance liquid chromatography (UHPLC) of the infusion showed rosmarinic acid, caffeic acid, and cichoric acid to be the main compounds aside from polymethoxylated flavones. Rosmarinic acid was quantified in the tea preparations with 243 ± 22 µg/mL, indicating sufficient reproducibility of the preparation of the infusion. Urine samples were obtained during the biomedical study on day 1 (control urine, prior to Java tea intake), 3, 6 and 8. Antiadhesive activity of the urine samples was quantified by flowcytometric assay using pre-treated UPEC NU14 and human T24 bladder cells. Pooled urine samples indicated significant inhibition of bacterial adhesion on day 3, 6 and 8. The urine samples had no influence on the invasion of UPEC into host cells. Bacterial proliferation was slightly reduced after 24 h incubation with the urine samples. Gene expression analysis (qPCR) revealed strong induction of fitness and motility gene fliC and downregulation of hemin uptake system chuT. These data correlate with previously reported datasets from in vitro transcriptomic analysis. Increased bacterial motility was monitored using a motility assay in soft agar with UPEC UTI89. The intake of Java tea had no effect on the concentration of Tamm-Horsfall Protein in the urine samples. The present study explains the antiadhesive and anti-infective effect of the plant extract by triggering UPEC from a sessile lifestyle into a motile bacterial form, with reduced adhesive capacity.

Dietary sinensetin and polymethoxyflavonoids: Bioavailability and potential metabolic syndrome-related bioactivity

Sinensetin is among the most ubiquitous polyphenols in citrus fruit and recently has been extensively studied for its ability to prevent or treat diseases. The current literature on the bioavailability of sinensetin and its derivatives was reviewed and the potential ameliorative effects of metabolic syndrome in humans were evaluated. Sinensetin and its derivatives mainly aggregated in the large intestine and extensively metabolized through gut microbiota (GM) and the liver. So intestinal microorganisms had a significant influence on the absorption and metabolism of sinensetin. Interestingly, not only GM acted on sinensetin to metabolize them, but sinensetin also regulated the composition of GM. Thus, sinensetin was metabolized as methyl, glucuronide and sulfate metabolites in the blood and urine. Furthermore, sinensetin was reported to have the beneficial effect of ameliorating metabolic syndromes, including disorders of lipid metabolism (obesity, NAFLD, atherosclerosis), glucose metabolism disorder (insulin resistant) and inflammation, in terms of improving the composition of intestinal flora and modulating metabolic pathway factors in relevant tissues. The present work strongly elucidated the potential mechanism of sinensetin in improving metabolic disorders and supported the contribution of sinensetin to health benefits, thus offering a better perspective in understanding the role played by sinensetin in human health.

Therapeutic Effectiveness of Sinensetin Against Cancer and Other Human Complications: A Review of Biological Potential and Pharmacological Activities

BACKGROUND

Plant and their active phytoproducts have been used in modern medicine and playing an important role in the health sectors since a very early age. Human beings need a considerable amount of these plant-based phytochemicals for their health. The flavonoidal class phytochemical is an important class of natural products in modern healthcare because of their different pharmacological activities and health benefits. Flavonoidal class phytochemicals have been used to treat diabetes and related secondary complications in humans. Flavonoids have antiapoptotic, anti-hyperlipidemic, anti-inflammatory, and anti-oxidant potential in the health sectors. Sinensetin, also called 3',4',5,6,7-pentametoksiflavon is a colorless compound with a molecular weight 372.37g/mol and is found to be present in the Orthosiphon stamineus.

METHODS

In the present investigation, we aim to collect scientific information on sinensetin and analyze it for its biological potential and therapeutic benefits against various types of disorders and complications. Medicinal importance and pharmacological activities data have been collected and analyzed in the present work for sinensetin through literature data analysis of different research works. Google Science Direct, PubMed, Scopus, and Google Scholar were mainly searched to collect the scientific information in the present work. The present work analyzed sinensetin biological potential, pharmacological activities, and analytical aspects.

RESULTS

Literature data analysis of different scientific research works revealed the biological potential of phytochemicals in medicine, including flavonoids. Sinensetin has anti-tumor, antiinflammatory, anti-oxidant, anti-diabetic, and antibacterial activities through their testing in different in vitro and in vivo models. Sinensetin has physiological functions, including anti-oxidant, antiinflammation, and anti-cancer potential in medicine. Scientific data analysis signified the biological importance of sinensetin against tumors, gastric cancer, colorectal cancer, breast cancer, diabetes, influenza H1N1 infection, obesity, inflammation, colitis, brain disorders, and microbial infections. Further biological potential of sinensetin on enzymes and angiogenesis has been analyzed in the present work. Sinensetin was isolated through different analytical and extraction techniques, including chromatographic techniques.

CONCLUSION

Literature data analysis signified sinensetin's biological potential and pharmacological activities in medicine.

Biotransformation and Quantification of Sinensetin and Its Metabolites in Plasma, Urine, and Feces of Rats

As one of the major polymethoxyflavones in citrus peels, sinensetin (Sin) has been reported to possess numerous bioactivities. However, its detailed in vivo metabolic fate has not been uncovered yet. In the present study, the possible metabolites of Sin were synthesized, and all five mono-demethylated metabolites were successfully identified via ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis in rats fed with 100 mg/(kg·bw) Sin. The excretion and pharmacokinetic studies were then carried out to quantitatively investigate their variation in content with time in urine, feces, and plasma samples. Results showed that 4'-demethylsinensetin, 6-demethylsinensetin, and 3'-demethylsinensetin were the three most abundant metabolites generated in the above-mentioned biological samples. In addition, the total amount of Sin with its metabolites showed a significantly higher content in urine than in feces, indicating that Sin may be easily absorbed in the small intestine.

Pharmacokinetics and Metabolites of 12 Bioactive Polymethoxyflavones in Rat Plasma

Polymethoxyflavones (PMFs) are a subgroup of flavonoids possessing various health benefits. 3,5,7,4'-Tetramethoxyflavone (1), 5,6,7,4'-tetramethylflavone (2), 3,7,3',4'-tetramethoxyflavone (3), 5,7,3',4'-tetramethoxyflavone (4), 5-hydroxy-3,7,2',4'-tetramethoxyflavone (5), 3,5,7,2',4'-pentamethoxyflavone (6), 5-hydroxy-3,7,3',4'-tetramethoxyflavone (7), 3-hydroxy-5,7,3',4'-tetramethylflavone (8), 3,5,7,3',4'-pentamethoxyflavone (9), 5-hydroxy-3,7,3',4',5'-pentamethoxyflavone (10), 3-hydroxy-5,7,3',4',5'-pentamethoxyflavone (11), and 3,5,7,3',4',5'-hexamethoxylflavone (12) were 12 bioactive and available PMFs. The aim of this study was to investigate the pharmacokinetic, metabolite, and antitumor activities as well as the structure-pharmacokinetic-antitumor activity relationships of these 12 PMFs to facilitate further studies of their medicinal potentials. The cytotoxicity of PMFs with a hydroxy group toward HeLa, A549, HepG2, and HCT116 cancer cell lines was generally significantly more potent than that of PMFs without a hydroxy group. Compounds 5, 7, 8, 10, and 11 were all undetectable in rat plasma, while compounds 1-4, 6, 9, and 12 were detectable. Both the number and position of hydroxy and methoxy groups played an important role in modulating PMF pharmacokinetics and metabolites.

Citrus flavonoids and the intestinal barrier: Interactions and effects

The intestinal barrier plays a central role in sustaining gut homeostasis and, when dysfunctional, may contribute to diseases. Dietary flavonoids derived from Citrus genus represent one of the main naturally occurring phytochemicals with multiple potential benefits for the intestinal barrier function. In the intestine, citrus flavonoids (CFs) undergo ingestion from the lumen, biotransformation in the epithelial cells and/or crosstalk with luminal microbiota to afford various metabolites that may in turn exert protective actions on gut barrier along with their parental compounds. Specifically, the health-promoting properties of CFs and their metabolic bioactives for the intestinal barrier include their capacity to (a) modulate barrier permeability; (b) protect mucus layer; (c) regulate intestinal immune system; (d) fight against oxidative stress; and (e) positively shape microbiome and metabolome. Notably, local effects of CFs can also generate systemic benefits, for instance, improvement of gut microbial dysbiosis helpful to orchestrate gut homeostasis and leading to alleviation of systemic dysmetabolism. Given the important role of the intestinal barrier in overall health, further understanding of underlying action mechanisms and ultimate health effects of CFs as well as their metabolites on the intestine is of great significance to future application of citrus plants and their bioactives as dietary supplements and/or functional ingredients in medical foods.

Metabolite Profiling of Naringin in Rat Urine and Feces Using Stable Isotope-Labeling-Based Liquid Chromatography-Mass Spectrometry

Naringin has been documented to possess various bioactivities. Due to thorny endogenous interferences, the metabolism pathways of naringin and exact amounts of derived phenolic catabolites have not been definitely assigned. In this work, stable isotope-labeling-based liquid chromatography-mass spectrometry methods were developed to eliminate the endogenous interferences. [2',3',5',6'-D₄]-naringin was orally administrated to rats. Urine and feces samples were collected and then analyzed with ultrahigh-performance liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (UHPLC-Q-TOF-MS/MS). A total of 21 flavonoid metabolites and 11 phenolic catabolites were screened. The metabolism and catabolism pathways were proposed. Furthermore, deuterated naringin and its main metabolites were determined with rapid resolution liquid chromatography tandem triple quadrupole mass spectrometry (RRLC-QqQ-MS/MS). The overall recovery of ingested deuterated naringin was calculated as 56.9% without endogenous interferences. The obtained results provide essential information for further pharmacological studies of naringin.

Simultaneously Quantitative Analysis of Naringin and Its Major Human Gut Microbial Metabolites Naringenin and 3-(4'-Hydroxyphenyl) Propanoic Acid via Stable Isotope Deuterium-Labeling Coupled with RRLC-MS/MS Method

Widespread in citrus fruits, naringin, a natural 2,3-dihydroflavonoid, is of particular interest to scientists and has a broad range of beneficial bioactivities to health. Orally administered naringin remains in the gut tract for a relatively long time because of its low bioavailability. Under the metabolism mediated by human gut microbiota, naringin could be an active precursor for derived metabolites to play important physiological roles. However, naringin and its metabolites are hard to accurately quantify due to severe endogenic interference. In this study, an analytical rapid resolution liquid chromatography tandem mass spectrometry (RRLC-MS/MS) method coupled with stable isotope deuterium-labeling is developed and validated to simultaneously quantify naringin as well as its major human gut microbial metabolites naringenin and 3-(4'-hydroxyphenyl) propanoic acid. By eliminating the matrix interferences, this strategy not only confirms naringenin and 3-(4'-hydroxyphenyl) propanoic acid as the predominant metabolites which contribute to the pharmacological effects of naringin but also provides a suitable choice for other flavonoid pharmacokinetics study.

Polymethoxylated flavones from Orthosiphon stamineus leaves as antiadhesive compounds against uropathogenic E. coli

Aqueous and acetone extracts of O. stamineus leaves reduce the adhesion of uropathogenic E. coli (UPEC, strain UTI89) to T24 bladder cells significantly (IC₂₅ ~ 524 mg/mL, resp. 40 μg/mL). The acteonic extract had no cytotoxic effects against UPEC in concentrations that inhibited the bacterial adhesion. The extract significantly reduced the gene expression of fimH, fimC, fimD, csgA and focG, which are strongly involved in the formation of bacterial adhesins. The antiadhesive effect was due to the presence of polymethoxylated flavones, enriched in the acetonic extract. Five flavones have been isolated by fast centrifugal partition chromatography, followed by preparative HPLC. Eupatorin, ladanein, salvigenin, sinensetin, 5,6,7,4'-tetramethoxyflavone and 5-hydroxy-6,7,3',4'-tetramethoxyflavone were identified as the main polymethoxylated flavones. With the exception of eupatorin, all of these flavones reduced the bacterial adhesion in a concentration depending manner, indicating that B-ring hydroxylation and methoxylation seems to have a major impact on the antiadhesive activity. In addition, this was confirmed by investigation of the flavones chrysoeriol and diosmetin, which had only very weak antiadhesive activity. From these data, Orthosiphon extracts can be assessed to have a pronounced antiadhesive activity against UPEC, based on a variety of polymethoxylated flavones.

Identification of naringin metabolites mediated by human intestinal microbes with stable isotope-labeling method and UFLC-Q-TOF-MS/MS

Widely presented in medicinal plants, naringin is one of the major flavanones with various pharmaceutical bioactivities. After oral administration, naringin predominantly undergoes metabolisms mediated by liver cytochrome P450 and gut microbes, while its human microbes-mediated metabolic profiling is still largely obscure due to the endogenous interferences, which makes it extremely difficult to analyze metabolites precisely. In this study, we aim of systematically investigating the biotransformation of naringin mediated by human intestinal microbes through applying stable isotope-labeling method. [2',3',5',6'-D₄]naringin was synthesized and incubated anaerobically with human gut microbes. A total of 13 microbial metabolites were detected and identified by UFLC-Q-TOF-MS/MS, among which 5 were reported for the first time. Furthermore, the proposed metabolic pathway revealed that naringin went through extensive phase I metabolism in human intestinal microbes. Of note, diverse metabolic profiles of naringin among human participants were obtained, which could be attributed to the distinct gut microbiota compositions of individuals.

Polymethoxyflavones: Novel β-Secretase (BACE1) Inhibitors from Citrus Peels

Beta-site amyloid precursor protein (APP) cleaving enzyme1 (BACE1) catalyzes the rate-limiting step of amyloid-β protein (Aβ) generation, and is considered as a prime target for Alzheimer’s disease (AD). In search of a candidate for AD prevention, our efforts exploring the natural BACE1 inhibitor have led to the finding of nobiletin, tangeretin, and sinensetin—representative compounds of polymethoxyflavones (PMFs). Tangeretin exhibited the strongest BACE1 inhibition (IC₅₀, 4.9 × 10⁻⁵ M), followed by nobiletin and sinensetin with IC₅₀ values of 5.9 × 10⁻⁵ M and 6.3 × 10⁻⁵ M, respectively. In addition, all compounds reacted in a non-competitive manner with the substrate. Docking analysis results for complexes with BACE1 indicated that SER10 and THR232 residues of BACE1 hydrogen bonded with two oxygen atoms of tangeretin, while three additional BACE1 residues (ALA157, VAL336 and THR232) interacted with three oxygen atoms of nobiletin. Furthermore, sinensetin formed four hydrogen bonds through nitrogen atoms of TYR71, LYS75, and TRP76, and an oxygen atom of TYR198. Furthermore, the lowest-energy conformations of the most proposed complexes of sinensetin, nobiletin, and tangeretin with BACE1 were −7.2, −7.0, and −6.8 kcal/mol, respectively. Taken together, our results suggest that these polymethoxyflavones (PMFs) might be considered as promising BACE1 inhibitory agents that could lower Aβ production in AD.

Disease chemopreventive effects and molecular mechanisms of hydroxylated polymethoxyflavones

Recent increasing attention in research of polymethoxyflavones (PMFs) from Citrus genus because of their wide range of biological properties has been reported in various studies. Hydroxylated PMFs are unique flavones and recognized as the methoxy group of PMFs that is substituted for hydroxyl one. Hydroxylated PMFs are naturally existed in citrus peel and other plants as well as occurred as metabolites of their PMFs counterparts. Several in vitro and in vivo studies have documented the chemopreventive effects of hydroxylated PMFs including anti-cancer, anti-inflammation, anti-atherosclerosis, and neuroprotection. They function to regulate cell death, proliferation, differentiation, repair, and metabolism through acting on modulation of signaling cascade, gene transcription, and protein function and enzyme activity. The mechanisms of action of hydroxylated PMFs in disease chemoprevention depend on their structure, the number, and position of hydroxyl group. Although the efficacy of hydroxylated PMFs in chemoprevention and the oral bioavailability requires further investigation, they still provide great promise for improving human health. This review highlights the recent published data of hydroxylated PMFs with chemopreventive potential and the underlying mechanism involved.

Exploration of Pharmacophore in Chrysosplenol C as Activator in Ventricular Myocyte Contraction

Chrysosplenol C (4',5,6-trihydroxy-3,3',7-trimethoxyflavone) isolated from Miliusa balansae has unique structural features as a reversible inotropic agent independent of β-adrenergic signaling and with selective activation of cardiac myosin ATPase. Hence, a series of chrysosplenol analogues were synthesized and explored for identification of pharmacophore that is essential for the increasing contractility in rat ventricular myocytes. Analogue 7-chloro-2-(3-hydroxyphenyl)-3-methoxy-4H-chromen-4-one showed highly potent contractility (54.8% at 10 μM) through activating cardiac myosin ATPase (38.7% at 10 μM). Our systematic structure-activity relationship study revealed that flavonoid nucleus of chrososplenol C appears to be an essential basic skeleton and hydrophobic substituent at position 7 of chromenone such as methoxy or chloro enhances the activity. Additionally, our ATPase study suggested that these chrysosplenol analogues have selectivity toward cardiac myosin activation. Thus, the novel flavonone with 3-/7-hydrophobic substituent and 3'-hydrogen bonding donor function is a novel scaffold for discovery of a new positive inotropic agent.

Stable isotope labeling strategy for curcumin metabolite study in human liver microsomes by liquid chromatography-tandem mass spectrometry

The identification of drug metabolites is very important in drug development. Nowadays, the most widely used methods are isotopes and mass spectrometry. However, the commercial isotopic labeled reagents are usually very expensive, and the rapid and convenient identification of metabolites is still difficult. In this paper, an (18)O isotope labeling strategy was developed and the isotopes were used as a tool to identify drug metabolites using mass spectrometry. Curcumin was selected as a model drug to evaluate the established method, and the (18)O labeled curcumin was successfully synthesized. The non-labeled and (18)O labeled curcumin were simultaneously metabolized in human liver microsomes (HLMs) and analyzed by liquid chromatography/mass spectrometry (LC-MS). The two groups of chromatograms obtained from metabolic reaction mixture with and without cofactors were compared and analyzed using Metabolynx software (Waters Corp., Milford, MA, USA). The mass spectra of the newly appearing chromatographic peaks in the experimental sample were further analyzed to find the metabolite candidates. Their chemical structures were confirmed by tandem mass spectrometry. Three metabolites, including two reduction products and a glucuronide conjugate, were successfully detected under their specific HLMs metabolic conditions, which were in accordance with the literature reported results. The results demonstrated that the developed isotope labeling method, together with post-acquisition data processing using Metabolynx software, could be used for fast identification of new drug metabolites.