Limonin: A Review of Its Pharmacology, Toxicity, and Pharmacokinetics

Mechanism of Zhishi Xiebai Guizhi decoction to treat atherosclerosis: Insights into experiments, network pharmacology and molecular docking

ETHNOPHARMACOLOGICAL RELEVANCE

Zhishi Xiebai Guizhi Decoction (ZSXBGZD) is a traditional herbal manuscript used to treat cardiovascular disease, including atherosclerosis and coronary heart disease. The decoction has demonstrated its capability to protect arteries and resist atherosclerosis. Its mechanisms for anti-atherosclerosis effect, nevertheless, remain unknown.

AIMS OF THE STUDY

The goal of the present study is to explore the effectiveness of ZSXBGZD acting on atherosclerosis and its key components based on experimental verification and network pharmacology analysis.

MATERIALS AND METHODS

The ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and databases were used to identify chemical components in ZSXBGZD. Network pharmacological analysis and molecular docking were implemented in order to reveal the possible therapeutic targets of ZSXBGZD. To form the model of atherosclerosis, we gave Apolipoprotein E knocked out mice a high-fat diet. H&E staining was performed to observe the effects of ZSXBGZD on atherosclerosis. Immunofluorescence and Western blot were used to investigate whether ZSXBGZD could affect autophagy, apoptosis, AGE-RAGE signaling pathway and other related mechanisms.

RESULTS

In total, 30 core compounds were screened through intersecting UPLC-Q-TOF-MS and the databases. The anti-atherosclerotic effect of ZSXBGZD might relate to the AGE-RAGE signaling pathway via network pharmacology analysis. ZSXBGZD could inhibit apoptosis, activate autophagy and ease inflammation by modifying AGE-RAGE signaling pathway to reduce the area of atherosclerotic plaque.

CONCLUSION

ZSXBGZD could treat atherosclerosis by regulating autophagy and apoptosis via adjusting the AGE-RAGE signaling pathway.

Phellodendron chinense C.K.Schneid: An in vitro study on its anti-Helicobacter pylori effect

ETHNOPHARMACOLOGICAL RELEVANCE

Phellodendron chinense C.K.Schneid(P. chinense Schneid) is known in TCM as Huang Bo, is traditionally used to support gastrointestinal function and alleviate stomach-related ailments, including gastric ulcer bleeding and symptoms of gastroesophageal reflux disease. Helicobacter pylori (H. pylori) is classified by the WHO as a Group 1 carcinogen. However, the specific activity and mechanism of action of P. chinense Schneid against H. pylori infection remain unclear. It has been noted that Huangjiu processing may alter the bitter and cold properties of P. chinense Schneid, but its effect on antimicrobial activity requires further investigation. Additionally, it remains uncertain whether berberine is the sole antimicrobial active component of P. chinense Schneid.

AIM OF STUDY

This study aims to elucidate the anti-H. pylori infection activity of P. chinense Schneid, along with its mechanism of action and key antimicrobial active components.

MATERIALS AND METHODS

Phytochemical analysis was carried out by UPLC-MS/MS. HPLC was employed to quantify the berberine content of the extracts. Antimicrobial activity was assessed using the micro broth dilution method. Morphology was observed using SEM. The impact on urease activity was analyzed through in vitro urease enzyme kinetics. RT-qPCR was employed to detect the expression of virulence genes, including adhesin, flagellum, urease, and cytotoxin-related genes. The adhesion effect was evaluated by immunofluorescence staining and agar culture.

RESULTS

P. chinense Schneid exhibited strong antimicrobial activity against both antibiotic-sensitive and resistant H. pylori strains, with MIC ranging from 40 to 160 μg/mL. Combination with amoxicillin, metronidazole, levofloxacin, and clarithromycin did not result in antagonistic effects. P. chinense Schneid induced alterations in bacterial morphology and structure, downregulated the expression of various virulence genes, and inhibited urease enzyme activity. In co-infection systems, P. chinense Schneid significantly attenuated H. pylori adhesion and urease relative content, thereby mitigating cellular damage caused by infection. Huangjiu processing enhanced the anti-H. pylori activity of P. chinense Schneid. Besides berberine, P. chinense Schneid contained seven other components with anti-H. pylori activity, with palmatine exhibiting the strongest activity, followed by jatrorrhizine.

CONCLUSIONS

This study sheds light on the potential therapeutic mechanisms of P. chinense Schneid against H. pylori infection, demonstrating its capacity to disrupt bacterial structure, inhibit urease activity, suppress virulence gene transcription, inhibit adhesion, and protect host cells. The anti-H. pylori activity of P. chinense Schneid was potentiated by Huangjiu processing, and additional components beyond berberine were identified as possessing strong anti-H. pylori activity. Notably, jatrorrhizine, a core component of P. chinense Schneid, exhibited significant anti-H. pylori activity, marking a groundbreaking discovery.

Preparation of limonin monoclonal antibody and establishment of a sensitive icELISA for analyzing limonin in citrus and herbal samples

Limonin is an intensely bitter and highly oxidized tetracyclic triterpenoid secondary metabolite, which is abundant in the Rutaceae and Meliaceae, especially in Citrus. In order to detect limonin content in complex substrates such as citrus and traditional Chinese medicine, monoclonal antibodies specifically recognizing limonin were prepared and an indirect competitive enzyme-linked immunosorbent assay (icELISA) was established. The median inhibition concentration (IC50) was 5.40 ng/mL and the linear range was 1.25-23.84 ng/mL. The average recoveries from citrus peel and pulp samples were 95.9%-118.8% and 77.5%-113.1%, respectively. Moreover, the contents of limonin in 6 citrus samples and 4 herbal samples were analyzed by icELISA and UPLC-MS, and the results of the two methods were consistent. This validation is sufficient to demonstrate that the developed immunoassay is applicable for the detection of limonin in citrus and herbal samples and has the advantage of high efficiency, sensitivity, and convenience.

Chemical constituents from the twigs with leaves of Tetradium trichotomum

Twelve compounds, comprising of four new ones, 6β,7α-limondiol (1) and ethyl 19-hydroxyisoobacunoate diosphenol (2), N-benzoyl 3-prenyltyramine (9) and 9-O-methyl integrifoliodiol (12), were isolated from the twigs with leaves of Tetradium trichotomum. The structures were elucidated by analysis of MS, NMR, and single-crystal X-ray diffraction. Compounds 1, 6, 8, 9 and 12 exhibited immunosuppressive activities in vitro against the proliferation of ConA-induced T lymphocytes and LPS-induced B cells.

Enhancement of hepatoprotective activity of limonin from citrus seeds against acetaminophen-induced liver injury by HSCCC purification and liposomal encapsulation

Limonin is a natural tetracyclic triterpenoid compound in citrus seeds that presents hepatoprotective effects but is often discarded as agricultural waste because of its low content and low solubility. Herein, limonin with high purity (98.11%) from citrus seeds was obtained via purification by high-speed counter-current chromatography (HSCCC) and recrystallization. Limonin-loaded liposomes (Lip-LM) prepared by thin film hydration and high pressure homogenization method to enhance its solubility and hepatoprotective effect on APAP-induced liver injury (AILI). Lip-LM appeared as lipid nanoparticles under a transmission electron microscope, and showed well dispersed nano-scale size (69.04 ± 0.42 nm), high encapsulation efficiency (93.67% ± 2.51%), sustained release, fine stability. Lip-LM also exhibited significantly better hepatoprotective activity on AILI than free limonin in vivo. In summary, Lip-LM might be used as a potential hepatoprotective agent in the form of dietary supplement and provide an effective strategy to improve the potential value of citrus seeds.

Integrated bacterial transcriptome and host metabolome analysis reveals insights into "Candidatus Liberibacter asiaticus" population dynamics in the fruit pith of three citrus cultivars with different tolerance

"Candidatus Liberibacter asiaticus" (CLas), the causal agent of citrus Huanglongbing (HLB), is able to multiply to a high abundance in citrus fruit pith. However, little is known about the biological processes and phytochemical substances that are vital for CLas colonization and growth in fruit pith. In this study, CLas-infected fruit pith of three citrus cultivars ("Shatangju" mandarin, "Guanxi" pomelo, and "Shatian" pomelo) exhibiting different tolerance to CLas were collected and used for dual RNA-Seq and untargeted metabolome analysis. Comparative transcriptome analysis found that the activation of the CLas noncyclic TCA pathway and pathogenic-related effectors could contribute to the colonization and growth of CLas in fruit pith. The pre-established Type 2 prophage in the CLas genome and the induction of its CRISPR/cas system could enhance the phage resistance of CLas and, in turn, facilitate CLas population growth in fruit pith. CLas infection caused the accumulation of amino acids that were correlated with tolerance to CLas. The accumulation of most sugars and organic acids in CLas-infected fruit pith, which could be due to the phloem blockage caused by CLas infection, was thought to be beneficial for CLas growth in localized phloem tissue. The higher levels of flavonoids and terpenoids in the fruit pith of CLas-tolerant cultivars, particularly those known for their antimicrobial properties, could hinder the growth of CLas. This study advances our understanding of CLas multiplication in fruit pith and offers novel insight into metabolites that could be responsible for tolerance to CLas or essential to CLas population growth.IMPORTANCECitrus Huanglongbing (HLB, also called citrus greening disease) is a highly destructive disease currently threatening citrus production worldwide. HLB is caused by an unculturable bacterial pathogen, "Candidatus Liberibacter asiaticus" (CLas). However, the mechanism of CLas colonization and growth in citrus hosts is poorly understood. In this study, we utilized the fruit pith tissue, which was able to maintain the CLas at a high abundance, as the materials for dual RNA-Seq and untargeted metabolome analysis, aiming to reveal the biological processes and phytochemical substances that are vital for CLas colonization and growth. We provided a genome-wide CLas transcriptome landscape in the fruit pith of three citrus cultivars with different tolerance and identified the important genes/pathways that contribute to CLas colonization and growth in the fruit pith. Metabolome profiling identified the key metabolites, which were mainly affected by CLas infection and influenced the population dynamic of CLas in fruit pith.

Insights into the Mechanism of Action of the Degraded Limonoid Prieurianin

Limonoids are extremely diversified in plants, with many categories of products bearing an intact, rearranged or fragmented oxygenated scaffold. A specific subgroup of fragmented or degraded limonoids derives from the tetranortriterpenoid prieurianin, initially isolated from the tree Trichilia prieuriana but also found in other plants of the Meliaceae family, including the more abundant species Aphanamixis polystachya. Prieurianin-type limonoids include about seventy compounds, among which are dregeanin and rohitukin. Prieurianin and analogs exhibit insecticidal, antimicrobial, antiadipogenic and/or antiparasitic properties but their mechanism of action remains ill-defined at present. Previous studies have shown that prieurianin, initially known as endosidin 1, stabilizes the actin cytoskeleton in plant and mammalian cells via the modulation of the architecture and dynamic of the actin network, most likely via interference with actin-binding proteins. A new mechanistic hypothesis is advanced here based on the recent discovery of the targeting of the chaperone protein Hsp47 by the fragmented limonoid fraxinellone. Molecular modeling suggested that prieurianin and, to a lesser extent dregeanin, can form very stable complexes with Hsp47 at the protein-collagen interface. Hsp-binding may account for the insecticidal action of the product. The present review draws up a new mechanistic portrait of prieurianin and provides an overview of the pharmacological properties of this atypical limonoid and its chemical family.

Breaking CHIPS-Mediated immune evasion with tripterin to promote neutrophil chemotaxis against MRSA infection

Neutrophils are the most important innate immune cells in host defense against methicillin-resistant Staphylococcus aureus (MRSA). However, MRSA orchestrates precise and timely expression of a series of virulence factors, especially the chemotaxis inhibitory protein of Staphylococcus aureus (CHIPS), to evade neutrophil-mediated host defenses. Here, we demonstrated that tripterin, a plant-derived bioactive pentacyclic triterpenoid, had a low minimum inhibitory concentration (MIC) of 1.28 µg/mL and displayed excellent anti-MRSA activity in vitro and in vivo. RNA-seq and further knockdown experiments revealed that tripterin could dramatically downregulate the expression of CHIPS by regulating the SaeRS two-component regulatory system, thereby enhancing the chemotactic response of neutrophils. Furthermore, tripterin also displayed a potential inhibitory effect on biofilm components to enhance neutrophil infiltration into the interior of the biofilm. In a mouse bacteremia model, tripterin could still maintain an excellent therapeutic effect that was significantly better than that of the traditional antibiotic vancomycin. Overall, these results suggest that tripterin possesses a superior antibacterial activity via breaking CHIPS-mediated immune evasion to promote neutrophil chemotaxis, thus providing a novel strategy for combating serious pathogenic infections.

Limonin alleviates high-fat diet-induced dyslipidemia by regulating the intestinal barrier via the microbiota-related ILC3-IL22-IL22R pathway

High-fat diet (HFD)-induced dyslipidemia is frequently accompanied by gut microbiota dysbiosis and a compromised gut barrier. Enhancing the intestinal barrier function emerges as a potential therapeutic approach for dyslipidemia. The ILC3-IL22-IL22R pathway, which responds to dietary and microbial signals, has not only attracted attention for its crucial role in maintaining the intestinal barrier, but recent reports have also suggested its potential in regulating lipid metabolism. Limonin is derived from the Chinese herb Evodiae fructus, which has shown potential in ameliorating dysbiosis of serum lipids. However, its underlying mechanisms remain elusive. Consequently, targeting the ILC3-IL22-IL22R pathway to enhance intestinal barrier function holds promise as a therapeutic approach for dyslipidemia. In this study, male C57BL/6 mice were subjected to a 16-week HFD to induce dyslipidemia and concurrently administered oral limonin. We discovered that limonin supplementation dramatically reduced serum lipid profiles in HFD-fed mice, significantly curbing HFD-induced weight gain and epididymal fat accumulation. Ileal histopathological evaluation indicated limonin's ameliorative effects on HFD-induced intestinal barrier impairment. Limonin also moderated the intestinal microbiota dysbiosis, which is characterized by the elevation of Firmicutes in HFD mice, and notably amplified the abundance of probiotic Lactobacillus. In addition, supported by flow cytometry and other analyses, we observed that limonin upregulated the ILC3-IL22-IL22R pathway, enhancing phosphorylated STAT3 (pSTAT3) in intestinal epithelial cells (IECs), thereby reducing lipid transporter expression. In conclusion, our study revealed that limonin exerted a promising preventive effect against HFD-induced dyslipidemia by the mitigation of the intestinal barrier function and intestinal microbiota, and its mechanism was related to the upregulation of the ILC3-IL22-IL22R pathway.

Limonin inhibits the stemness of cancer stem-like cells derived from colorectal carcinoma cells potentially via blocking STAT3 signaling

BACKGROUND

Limonin is one of the most abundant active ingredients of Tetradium ruticarpum. It exerts antitumor effects on several kinds of cancer cells. However, whether limonin exerts antitumor effects on colorectal cancer (CRC) cells and cancer stem-like cells (CSCs), a subpopulation responsible for a poor prognosis, is unclear.

AIM

To evaluate the effects of limonin on CSCs derived from CRC cells.

METHODS

CSCs were collected by culturing CRC cells in serum-free medium. The cytotoxicity of limonin against CSCs and parental cells (PCs) was determined by cholecystokinin octapeptide-8 assay. The effects of limonin on stemness were detected by measuring stemness hallmarks and sphere formation ability.

RESULTS

As expected, limonin exerted inhibitory effects on CRC cell behaviors, including cell proliferation, migration, invasion, colony formation and tumor formation in soft agar. A relatively low concentration of limonin decreased the expression stemness hallmarks, including Nanog and β-catenin, the proportion of aldehyde dehydrogenase 1-positive CSCs, and the sphere formation rate, indicating that limonin inhibits stemness without presenting cytotoxicity. Additionally, limonin treatment inhibited invasion and tumor formation in soft agar and in nude mice. Moreover, limonin treatment significantly inhibited the phosphorylation of STAT3 at Y705 but not S727 and did not affect total STAT3 expression. Inhibition of Nanog and β-catenin expression and sphere formation by limonin was obviously reversed by pretreatment with 2 μmol/L colievlin.

CONCLUSION

Taken together, these results indicate that limonin is a promising compound that targets CSCs and could be used to combat CRC recurrence and metastasis.

Mechanism underlying the effect of Pulsatilla decoction in hepatocellular carcinoma treatment: a network pharmacology and in vitro analysis

BACKGROUND

Currently, hepatocellular carcinoma (HCC) is associated with a poor prognosis. Moreover, there exist limited strategies for treating HCC. Pulsatilla decoction (PD), a traditional Chinese medicine formula, has been used to treat inflammatory bowel disease and several cancer types. Accordingly, we explored the mechanism of PD in HCC treatment via network pharmacology and in vitro experiments.

METHODS

Online databases were searched for gene data, active components, and potential target genes associated with HCC development. Subsequently, bioinformatics analysis was performed using protein-protein interaction and Network Construction and Kyoto Encyclopedia of Genes and Genomes (KEGG) to screen for potential anticancer components and therapeutic targets of PD. Finally, the effect of PD on HCC was further verified by in vitro experiments.

RESULTS

Network pharmacological analysis revealed that 65 compounds and 180 possible target genes were associated with the effect of PD on HCC. These included PI3K, AKT, NF-κB, FOS, and NFKBIA. KEGG analysis demonstrated that PD exerted its effect on HCC mainly via the PI3K-AKT, IL-17, and TNF signaling pathways. Cell viability and cell cycle experiments revealed that PD could significantly inhibit cancer cell proliferation and kill HCC cells by inducing apoptosis. Furthermore, western blotting confirmed that apoptosis was mediated primarily via the PI3K-AKT, IL-17, and TNF signaling pathways.

CONCLUSION

To the best of our knowledge, this is the first study to elucidate the molecular mechanism and potential targets of PD in the treatment of HCC using network pharmacology.

An overview of limonoid synthetic derivatives as promising bioactive molecules

Limonoids, a class of abundant natural tetracyclic triterpenoids, present diverse biological activity and provide a versatile platform amenable by chemical modifications for clinical use. Among all of the limonoids isolated from natural sources, obacunone, nomilin, and limonin are the primary hub of limonoid-based chemical modification research. To date, more than 800 limonoids analogs have been synthesized, some of which possess promising biological activities. This review not only discusses the synthesis of limonoid derivatives as promising therapeutic candidates and details the pharmacological studies of their underlying mechanisms from 2002 to 2022, but also proposes a preliminary limonoid synthetic structure-activity relationship (SAR) and provides future direction of limonoid derivatization research.

Limonin mitigates cisplatin-induced acute kidney injury through metabolic reprogramming

BACKGROUND

Acute kidney injury (AKI) is a known complication of cisplatin administration; currently, there are no effective ways to prevent it. Therefore, it largely limited the use of cisplatin in chemotherapy in the clinic. In this study, we reported that Limonin, a triterpenoid compound extracted from citrus, alleviated cisplatin-induced AKI through metabolic reprogramming in the diseased kidneys.

METHODS

Cisplatin was employed to induce AKI in mice. Three groups were set up: Sham, cisplatin + vehicle, and cisplatin + Limonin. Using UHPLC-TOF/MS, we conducted metabolomics to profile the kidneys' endogenous metabolites and metabolic pathways. A network pharmacological method was performed to identify the targets of Limonin on AKI. The human proximal tubular epithelial cell line (HK-2) was applied for in vitro studies.

RESULTS

Limonin preserved serum creatinine and blood urea nitrogen levels after cisplatin-induced AKI. Employing metabolomics, we identified 33 endogenous differentially expressed metabolites and 7 significantly disturbed metabolic pathways in the diseased kidneys within three groups. After AKI, Limonin significantly reduced linoleic acid and its downstream product, arachidonic acid, thus exerting a protective effect on the kidney. The network pharmacological method identified CYP3A4 as a key target of Limonin in treating AKI, while CYP3A4 also serve as a mediator of arachidonic acid metabolism. In vitro, Limonin markedly reduced the level of arachidonic acid and HK-2 cell apoptosis triggered by cisplatin, mainly related to the targeted inhibition of CYP3A4-mediated arachidonic acid metabolism.

CONCLUSION

Limonin ameliorates cisplatin-induced AKI by inhibiting CYP3A4 activity to regulate arachidonic acid metabolism, ultimately preserving kidney function.

On the Efficiency of the Density Functional Theory (DFT)-Based Computational Protocol for 1H and 13C Nuclear Magnetic Resonance (NMR) Chemical Shifts of Natural Products: Studying the Accuracy of the pecS-n (n = 1, 2) Basis Sets

The basis set issue has always been one of the most important factors of accuracy in the quantum chemical calculations of NMR chemical shifts. In a previous paper, we developed new pecS-n (n = 1, 2) basis sets purposed for the calculations of the NMR chemical shifts of the nuclei of the most popular NMR-active isotopes of 1-2 row elements and successfully approbated these on the DFT calculations of chemical shifts in a limited series of small molecules. In this paper, we demonstrate the performance of the pecS-n (n = 1, 2) basis sets on the calculations of as much as 713 1H and 767 13C chemical shifts of 23 biologically active natural products with complicated stereochemical structures, carried out using the GIAO-DFT(PBE0) approach. We also proposed new alternative contraction schemes for our basis sets characterized by less contraction depth of the p-shell. New contraction coefficients have been optimized with the property-energy consistent (PEC) method. The accuracies of the pecS-n (n = 1, 2) basis sets of both the original and newly contracted forms were assessed on massive benchmark calculations of proton and carbon chemical shifts of a vast variety of natural products. It was found that less contracted pecS-n (n = 1, 2) basis sets provide no noticeable improvement in accuracy. These calculations represent the most austere test of our basis sets as applied to routine calculations of the NMR chemical shifts of real-life compounds.

Limonin, a novel AMPK activator, protects against LPS-induced acute lung injury

AMP-activated protein kinase (AMPK) activation plays crucial roles in the treatment of many oxidative stress- and inflammation-induced diseases, including acute lung injury (ALI). Limonin is a naturally occurring tetracyclic triterpenoid extracted from the plants of Rutaceae and Meliaceae. Limonin also serves as an AMPK activator with anti-inflammatory and anti-oxidation effects. However, the potential beneficial effects of limonin on ALI and the possible mechanisms have never been disclosed till now. Here, the effects of limonin on lipopolysaccharide (LPS)-induced ALI in C57 BL/6 mice, plus bone marrow-derived macrophages (BMDM) stimulated with LPS to induce in vitro ALI model were investigated. Limonin significantly improved pulmonary function and alleviated lung pathological injury in LPS-induced mice. Meanwhile, limonin also markedly decreased inflammation and oxidative stress in lung tissues from LPS-treated mice. In vitro experiments also unveiled that limonin could decrease inflammation and oxidative stress in LPS-induced BMDM in a concentration-dependent manner. Mechanically, limonin could promote the activation of AMPKα and upregulate the expression of nuclear factor erythroid 2-related factor 2 (NRF2) in lung tissues and BMDM. Pharmacological inhibition of AMPKα by Compound C or AMPKα knockout could abolish the pulmonary protection from limonin during ALI. In conclusion, limonin mediates the activation of AMPKα/NRF2 pathway, providing an attractive therapeutic target for ALI in the future.

Limonin ameliorates cardiovascular dysfunction and remodeling in hypertensive rats

AIMS

Limonin is a tetracyclic triterpenoid isolated from citrus fruits. Here, the effects of limonin on cardiovascular abnormalities in nitric oxide-deficient rats induced by N^ω-Nitrol-arginine methyl ester (L-NAME) were explored.

MAIN METHODS

Male Sprague Dawley rats were given L-NAME (40 mg/kg, drinking water) for 3 weeks and then treated daily with polyethylene glycol (vehicle), limonin (50 or 100 mg/kg) or telmisartan (10 mg/kg) for two weeks.

KEY FINDINGS

Limonin (100 mg/kg) markedly reduced L-NAME-induced hypertension, cardiovascular dysfunction and remodeling in rats (P < 0.05). Increases in systemic angiotensin-converting enzyme (ACE) activity and angiotensin II (Ang II) and a reduction in circulating ACE2 were restored in hypertensive rats treated with limonin (P < 0.05). Reductions in antioxidant enzymes and nitric oxide metabolites (NOx) and increases in oxidative stress components induced by L-NAME were relieved by limonin treatment (P < 0.05). Limonin suppressed the increased expression of tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 in cardiac tissue and circulating TNF-α in rats that received L-NAME (P < 0.05). Changes in Ang II receptor type I (AT1R), Mas receptor (MasR), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ĸB) and NADPH oxidase subunit 2 (gp91^phox) protein expression in cardiac and aortic tissue were normalized by limonin (P < 0.05).

SIGNIFICANCE

In conclusion, limonin ameliorated L-NAME-induced hypertension, cardiovascular dysfunction and remodeling in rats. These effects were relevant to restorations of the renin-angiotensin system, oxidative stress and inflammation in NO-deficient rats. The molecular mechanisms are associated with the modulation of AT1R, MasR, NF-ĸB and gp91^phox protein expression in cardiac and aortic tissue.

Evolution-guided multiomics provide insights into the strengthening of bioactive flavone biosynthesis in medicinal pummelo

Pummelo (Citrus maxima or Citrus grandis) is a basic species and an important type for breeding in Citrus. Pummelo is used not only for fresh consumption but also for medicinal purposes. However, the molecular basis of medicinal traits is unclear. Here, compared with wild citrus species/Citrus-related genera, the content of 43 bioactive metabolites and their derivatives increased in the pummelo. Furthermore, we assembled the genome sequence of a variety for medicinal purposes with a long history, Citrus maxima 'Huazhouyou-tomentosa' (HZY-T), at the chromosome level with a genome size of 349.07 Mb. Comparative genomics showed that the expanded gene family in the pummelo genome was enriched in flavonoids-, terpenoid-, and phenylpropanoid biosynthesis. Using the metabolome and transcriptome of six developmental stages of HZY-T and Citrus maxima 'Huazhouyou-smooth' (HZY-S) fruit peel, we generated the regulatory networks of bioactive metabolites and their derivatives. We identified a novel MYB transcription factor, CmtMYB108, as an important regulator of flavone pathways. Both mutations and expression of CmtMYB108, which targets the genes PAL (phenylalanine ammonia-lyase) and FNS (flavone synthase), displayed differential expression between Citrus-related genera, wild citrus species and pummelo species. This study provides insights into the evolution-associated changes in bioactive metabolism during the origin process of pummelo.

Systematic analysis on the mechanism of Zhizi-Bopi decoction against hepatitis B via network pharmacology and molecular docking

PURPOSE

Zhizi-Bopi decoction (ZZBPD) is a classic herbal formula with wide clinical applications in treating liver diseases including hepatitis B. However, the mechanism needs to be elucidated.

METHODS

Chemical components of ZZBPD were identified by ultra-high-performance liquid chromatography coupled with time-of-flight mass spectrometry (UHPLC-TOF-MS). Then we used network pharmacology to identify their potential targets. Network construction, coupled with protein-protein interaction and enrichment analysis was used to identify representative components and core targets. Finally, molecular docking simulation was conducted to further refine the drug-target interaction.

RESULTS

One hundred and forty-eight active compounds were identified in ZZBPD, targeting 779 genes/proteins, among which 174 were related to hepatitis B. ZZBPD mainly influences the progression of hepatitis B through the hepatitis B pathway (hsa05161) via core anti-HBV targets (AKT1, PIK3CA, PIK3R1, SRC, TNF, MAPK1, and MAPK3). Enrichment analysis indicated that ZZBPD can also potentially regulate lipid metabolism and enhance cell survival. Molecular docking suggested that the representative active compounds can bind to the core anti-HBV targets with high affinity.

CONCLUSION

The potential molecular mechanisms of ZZBPD in hepatitis B treatment were identified using network pharmacology and molecular docking approaches. The results serve as an important basis for the modernization of ZZBPD.

Metabolomic Analysis of Phytochemical Compounds from Ethanolic Extract of Lime (Citrus aurantifolia) Peel and Its Anti-Cancer Effects against Human Hepatocellular Carcinoma Cells

Lime peels are food waste from lime product manufacturing. We previously developed and optimized a green extraction method for hesperidin-limonin-rich lime peel extract. This study aimed to identify the metabolomics profile of phytochemicals and the anti-cancer effects of ethanolic extract of lime (Citrus aurantifolia) peel against liver cancer cells PLC/PRF/5. The extract’s metabolomics profile was analyzed by using LC-qTOF/MS and GC-HRMS. The anti-cancer effects were studied by using MTT assay, Annexin-PI assay, and Transwell-invasion assay. Results show that the average IC50(s) of hesperidin, limonin, and the extract on cancer cells’ viability were 165.615, 188.073, and 503.004 µg/mL, respectively. At the IC50 levels, the extract induced more apoptosis than those of pure compounds when incubating for 24 and 48 h (p < 0.0001). A combination of limonin and hesperidin showed a synergistic effect on apoptosis induction (p < 0.001), but the effect of the combination was still less than that of the extract at 48 h. Furthermore, the extract significantly inhibited cancer cell invasion better than limonin but equal to hesperidin. At the IC50 level, the extract contains many folds lower amounts of hesperidin and limonin than the IC50 doses of the pure compounds. Besides limonin and hesperidin, there were another 60 and 22 compounds detected from the LCMS and GCMS analyses, respectively. Taken altogether, the superior effect of the ethanolic extract against liver cancer cells compared to pure compound likely results from the combinatorial effects of limonin, hesperidin, and other phytochemical components in the extract.

Post-Cyclization Skeletal Rearrangements in Plant Triterpenoid Biosynthesis by a Pair of Branchpoint Isomerases

Triterpenoids possess potent biological activities, but their polycyclic skeletons are challenging to synthesize. The skeletal diversity of triterpenoids in plants is generated by oxidosqualene cyclases based on epoxide-triggered cationic rearrangement cascades. Normally, triterpenoid skeletons then remain unaltered during subsequent tailoring steps. In contrast, the highly modified triterpenoids found in Sapindales plants imply the existence of post-cyclization skeletal rearrangement enzymes that have not yet been found. We report here a biosynthetic pathway in Sapindales plants for the modification of already cyclized tirucallane triterpenoids, controlling the pathway bifurcation between different plant triterpenoid classes. Using a combination of bioinformatics, heterologous expression in plants and chemical analyses, we identified a cytochrome P450 monooxygenase and two isomerases which harness the epoxidation-rearrangement biosynthetic logic of triterpene cyclizations for modifying the tirucallane scaffold. The two isomerases share the same epoxide substrate made by the cytochrome P450 monooxygenase CYP88A154, but generate two different rearrangement products, one containing a cyclopropane ring. Our findings reveal a process for skeletal rearrangements of triterpenoids in nature that expands their scaffold diversity after the initial cyclization. In addition, the enzymes described here are crucial for the biotechnological production of limonoid, quassinoid, apoprotolimonoid, and glabretane triterpenoids.

Naringenin and Hesperidin as Promising Alternatives for Prevention and Co-Adjuvant Therapy for Breast Cancer

Citrus (genus Citrus L.) fruits are essential sources of bioactive compounds with antioxidant properties, such as flavonoids. These polyphenolic compounds are divided into subclasses, in which flavanones are the most prominent. Among them, naringenin and hesperidin are emerging compounds with anticancer potential, especially for breast cancer (BC). Several mechanisms have been proposed, including the modulation of epigenetics, estrogen signaling, induction of cell death via regulation of apoptotic signaling pathways, and inhibition of tumor invasion and metastasis. However, this information is sparse in the literature and needs to be brought together to provide an overview of how naringenin and hesperidin can serve as therapeutic tools for drug development and as a successful co-adjuvant strategy against BC. This review detailed such mechanisms in this context and highlighted how naringenin and hesperidin could interfere in BC carcinogenesis and be helpful as potential alternative therapeutic sources for breast cancer treatment.

Limonin ameliorates indomethacin-induced intestinal damage and ulcers through Nrf2/ARE pathway

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) can cause intestinal damage and ulcers and the incidence is increasing. Limonin plays an important role in the regulation of inflammatory diseases, but it has not been reported in the treatment of intestinal injury and ulcers.

METHODS

Indomethacin (INDO) induced intestinal injury and ulcer model in rats. The indexes related to intestinal injury were detected. Western blot and molecular docking techniques were used to detect the docking between Limonin and Nrf2. Next, ML385, an inhibitor of Nrf2/ARE signaling pathway, was applied to treat intestinal epithelial IEC-6 cells induced by INDO. And CCK8, Western blot, TUNEL, ELISA, DCFH-DA assay, kits, and immunofluorescence were conducted to detect cell activity, apoptosis, inflammatory response, oxidative stress, and tight junction again.

RESULTS

INDO can significantly induce intestinal ulcerative lesions in rats. Limonin could improve intestinal ulcerative lesions induced by INDO in rats. Limonin could reduce INDO-induced inflammatory response and oxidative stress in the small intestine of rats, and improve the intestinal barrier dysfunction induced by INDO. Limonin could dock with Nrf2 structure and activate Nrf2/ARE signaling pathway. ML385 could reverse the protective effect of Limonin against INDO-induced cell damage.

CONCLUSION

Limonin ameliorates INDO-induced intestinal damage and ulcers through Nrf2/ARE pathway.

Traditional Chinese medicine Euodiae Fructus: botany, traditional use, phytochemistry, pharmacology, toxicity and quality control

Euodiae Fructus, referred to as "Wuzhuyu" in Chinese, has been used as local and traditional herbal medicines in many regions, especially in China, Japan and Korea, for the treatment of gastrointestinal disorders, headache, emesis, aphtha, dermatophytosis, dysentery, etc. Substantial investigations into their chemical and pharmacological properties have been performed. Recently, interest in this plant has been focused on the different structural types of alkaloids like evodiamine, rutaecarpine, dehydroevodiamine and 1-methyl-2-undecyl-4(1H)-quinolone, which exhibit a wide range of pharmacological activities in preclinical models, such as anticancer, antibacterial, anti-inflammatory, anti-cardiovascular disease, etc. This review summarizes the up-to-date and comprehensive information concerning the botany, traditional uses, phytochemistry, pharmacology of Euodiae Fructus together with the toxicology and quality control, and discusses the possible direction and scope for future research on this plant.

Network Pharmacology to Reveal the Molecular Mechanisms of Rutaceous Plant-derived Limonin Ameliorating Non-alcoholic Steatohepatitis

BACKGROUND

Limonin shows promise in alleviating non-alcoholic fatty liver disease. We investigated the mechanisms of limonin against non-alcoholic steatohepatitis (NASH) using network pharmacology and molecular docking.

METHODS

Public databases provided NASH- and limonin-associated targets. VennDiagram identified potential limonin targets for NASH. Enrichment analysis explored the limonin-NASH relationship. PPI network analysis, CytoHubba models, and bioinformatics identified hub genes for NASH treatment. Molecular docking assessed limonin's binding ability to hub targets.

RESULTS

We found 37 potential limonin targets in NASH, involved in oxidative stress, inflammation, and signaling pathways. PPI network analysis revealed seven hub genes (STAT3, NFKBIA, MTOR, TLR4, CASP8, PTGS2, NFKB1) as NASH treatment targets. Molecular docking confirmed limonin's binding to STAT3, CASP8, and PTGS2. Animal experiments on high-fat diet mice showed limonin reduced hepatic steatosis, lipid accumulation, and expression of p-STAT3/STAT3, CASP8, and PTGS2.

CONCLUSION

Limonin's therapeutic effects in NASH may stem from its antioxidant and anti-inflammatory properties. STAT3, CASP8, and PTGS2 are potential key targets for NASH treatment, warranting further investigation.

Status of research on natural protein tyrosine phosphatase 1B inhibitors as potential antidiabetic agents: Update

Protein tyrosine phosphatase 1B (PTP1B) is a crucial therapeutic target for multiple human diseases comprising type 2 diabetes (T2DM) and obesity because it is a seminal part of a negative regulator in both insulin and leptin signaling pathways. PTP1B inhibitors increase insulin receptor sensitivity and have the ability to cure insulin resistance-related diseases. However, the few PTP1B inhibitors that entered the clinic (Ertiprotafib, ISIS-113715, Trodusquemine, and JTT-551) were discontinued due to side effects or low selectivity. Molecules with broad chemical diversity extracted from natural products have been reported to be potent PTP1B inhibitors with few side effects. This article summarizes the recent PTP1B inhibitors extracted from natural products, clarifying the current research progress, and providing new options for designing new and effective PTP1B inhibitors.

Integrated serum pharmacochemistry and investigation of the anti-gastric ulcer effect of Zuojin pill in rats induced by ethanol

CONTEXT

Zuojin Pill (ZJP) has been used to treat gastrointestinal problems in China for hundreds of years.

OBJECTIVE

To discover more potential active ingredients and evaluate the gastroprotective mechanisms of ZJP.

MATERIALS AND METHODS

An approach involving UPLC-Q-Orbitrap HRMS and serum pharmacochemistry was established to screen the multiple chemical constituents of ZJP. Male Sprague-Dawley (SD) rats were divided into six groups: normal control, ulcer control, omeprazole (30 mg/kg), and three ZJP groups (1.0, 2.0 and 4.0 g/kg). After oral treatment with ZJP or omeprazole for 7 days, all groups except the normal control group were orally administered 5 mL/kg ethanol to induce gastric ulceration. Histopathological assessment of gastric tissue was performed by haematoxylin and eosin staining. Antioxidant parameters and inflammatory mediators were determined using ELISA Kit and immunohistochemical analysis.

RESULTS

Ninety components were identified in ZJP. Among them, 23 prototypes were found in rat serum after oral administration of ZJP. The ulcer inhibition was over 90.0% for all the ZJP groups. Compared with the ulcer control rats, ZJP (4.0 g/kg) enhanced the antioxidant capacity of gastric tissue: superoxide dismutase (1.33-fold), catalase (2.61-fold), glutathione (2.14-fold), and reduced the malondialdehyde level (0.48-fold). Simultaneously, the ZJP meaningfully lowered the content of tumour necrosis factor-α (0.76-fold), interleukin-6 (0.66-fold), myeloperoxidase (0.21-fold), and nuclear factor kappa B (p65) (0.62-fold).

DISCUSSION AND CONCLUSIONS

This study showed ZJP could mitigate ethanol-induced rat gastric ulcers, which might benefit from the synergistic actions of multiple ingredients. The findings could support the quality control and clinical trials of ZJP.

Bioactivity-guided isolation of anti-inflammatory limonins from Chukrasia tabularis

Chukrasia tabularis is an economically important tree and widely cultured in the southeast of China. Its barks, leaves, and fruits are consumed as a traditional medicine and perceived as a valuable source for bioactive limonin compounds. The extracts from root barks of C. tabularis showed significant anti-inflammatory effect. The aim of this research was to explore the material basis of C. tabularis anti-inflammatory activity, and to purify and identify anti-inflammatory active ingredients. By a bioassay-guided isolation of dichloromethane fraction obtained two novel phragmalin limonins, Chukrasitin D and E (1 and 2), together with 12 known limonins (3-14). The chemical structure of these compounds is determined on the basis of extensive spectral analysis and chemical reactivity. In addition, the activities of these isolated limonins on the production of nitric oxide (NO), tumor necrosis factor alpha (TNF-α), and nuclear factor kappa B (NF-κB) in RAW264.7 cells induced by lipopolysaccharide (LPS) were evaluated. Limonins 1 and 2 indicated significant anti-inflammatory activity with IC50 values of 6.24 and 6.13 μM. Compound 1 notably inhibited the production of NF-κB, TNF-α and interleukin 6 (IL-6) in macrophages. The present results suggest that the root barks of C. tabularis exhibited anti-inflammatory effect and the limonins may be responsible for this activity.

Bioactive compounds as potential angiotensin-converting enzyme II inhibitors against COVID-19: a scoping review

Objective and design

The current study aimed to summarize the evidence of compounds contained in plant species with the ability to block the angiotensin-converting enzyme 2 (ACE-II), through a scoping review.

Methods

PubMed and Scopus electronic databases were used for the systematic search and a manual search was performed

Results

Studies included were characterized as in silico. Among the 200 studies retrieved, 139 studies listed after the exclusion of duplicates and 74 were included for the full read. Among them, 32 studies were considered eligible for the qualitative synthesis. The most evaluated class of secondary metabolites was flavonoids with quercetin and curcumin as most actives substances and terpenes (isothymol, limonin, curcumenol, anabsinthin, and artemisinin). Other classes that were also evaluated were alkaloid, saponin, quinone, substances found in essential oils, and primary metabolites as the aminoacid l-tyrosine and the lipidic compound 2-monolinolenin.

Conclusion

This review suggests the most active substance from each class of metabolites, which presented the strongest affinity to the ACE-II receptor, what contributes as a basis for choosing compounds and directing the further experimental and clinical investigation on the applications these compounds in biotechnological and health processes as in COVID-19 pandemic.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00011-022-01642-7.

Biosynthesis, distribution, nutritional and organoleptic properties of bitter compounds in fruit and vegetables

Compounds that confer a bitter taste on fruits and vegetables (FAVs) play crucial roles in both plant defense and health promotion. This review details the current knowledge of the distribution, properties (toxicity, pharmacological effects and receptors) and environmental plant responses relating to the biosynthesis, catabolism and transcriptional regulation of 53 bitter plant metabolites in diverse species of FAVs. Some bitter compounds, such as flavonoids, are common in all plant species and make a minor contribution to bitter flavor, but many are synthesized only in specific taxa. They make major contributions to the bitter taste of the corresponding species and some also have significant pharmacological effects. Levels of bitter metabolites are genetically determined, but various environmental cues can affect their final concentration during preharvest development and postharvest storage processes. Molecular approaches are helping to unravel the mechanisms of biosynthesis and regulation of bitter compounds in diverse crop species. This review not only discusses the theoretical basis for utilizing breeding programs and other agricultural technologies to produce FAVs with improved safety, favorable taste and healthier profiles, but also suggests new directions for the utilization of bitter compounds in FAVs for the development of natural pesticides and health-promoting medicines.

Mailuoshutong pill for varicocele-associated male infertility—Phytochemical characterisation and multitarget mechanism

Background: Varicocele (VC) is a relatively common and treatable cause of male infertility. Mailuoshutong pill (MLST), a traditional Chinese patent medicine, is widely used for treating varicose vein disease, but the underlying mechanism of MLST on varicocele-associated male infertility is unclear.

Objective: To reveal the phytochemical characterisation and multitarget mechanism of MLST on varicocele-associated male infertility.

Methods: The components in MLST were determined using UHPLC-MS/MS. Through network analysis, we constructed the “Drug-Components-Targets-Disease” network and predicted the potential biological functions and signaling pathways of MLST. Finally, the therapeutic effects and potential mechanisms of MLST were discovered by pharmacological experiments.

Results: By network analysis, the “Drug-Components-Targets-Disease” network was constructed, 62 components such as apigenin, limonin, kaempferol, and obacunoic acid may be the main active components of MLST for varicocele-associated male infertility, 28 targets such as VEGFA, PIK3CA, AKT1, and MTOR are considered as hub targets, signaling pathways such as HIF-1, Estrogen, PI3K/Akt, and mTOR may be key pathways for MLST against varicocele-associated male infertility. Through pharmacological experiments, we found that MLST ameliorated VC-induced testicular atrophy. Further histomorphology showed that MLST reduced VC-induced damage to testicular spermatogonia and seminiferous tubule, while MLST reduced ROS and MDA levels and increased antioxidant enzymes (GSH, GSH-Px, SOD, and CAT) levels. TUNEL staining and immunofluorescence showed that MLST reduced VC-induced apoptosis in testicular tissue, decreased BAX, and increased BCL2. Western blot results showed that MLST decreased the phosphorylation of PI3K, AKT, and mTOR proteins, and decreased the expression of HIF1α.

Conclusion: The phytochemical characterisation and multitarget mechanism of MLST on varicocele-associated male infertility were discovered using network analysis and pharmacological experiments. We verified that MLST can inhibit the activation of the PI3K/Akt/mTOR signaling pathway, reduce the expression of HIF1α, and further attenuate VC-induced oxidative stress and apoptosis in the testis. These findings provide evidence for the therapeutic role of MLST in varicocele-associated male infertility.

The genome of homosporous maidenhair fern sheds light on the euphyllophyte evolution and defences

Euphyllophytes encompass almost all extant plants, including two sister clades, ferns and seed plants. Decoding genomes of ferns is the key to deep insight into the origin of euphyllophytes and the evolution of seed plants. Here we report a chromosome-level genome assembly of Adiantum capillus-veneris L., a model homosporous fern. This fern genome comprises 30 pseudochromosomes with a size of 4.8-gigabase and a contig N50 length of 16.22 Mb. Gene co-expression network analysis uncovered that homospore development in ferns has relatively high genetic similarities with that of the pollen in seed plants. Analysing fern defence response expands understanding of evolution and diversity in endogenous bioactive jasmonates in plants. Moreover, comparing fern genomes with those of other land plants reveals changes in gene families important for the evolutionary novelties within the euphyllophyte clade. These results lay a foundation for studies on fern genome evolution and function, as well as the origin and evolution of euphyllophytes.

Untargeted LC-MS/MS-Based Multi-Informative Molecular Networking for Targeting the Antiproliferative Ingredients in Tetradium ruticarpum Fruit

The fruit of Tetradium ruticarpum (TR) is commonly used in Chinese herbal medicine and it has known antiproliferative and antitumor activities, which can serve as a good source of functional ingredients. Although some antiproliferative compounds are reported to be present in TR fruit, most studies only focused on a limited range of metabolites. Therefore, in this study, the antiproliferative activity of different extracts of TR fruit was examined, and the potentially antiproliferative compounds were highlighted by applying an untargeted liquid chromatography–tandem mass spectrometry (LC-MS/MS)-based multi-informative molecular networking strategy. The results showed that among different extracts of TR fruit, the EtOAc fraction F2-3 possessed the most potent antiproliferative activity against HL-60, T24, and LX-2 human cell lines. Through computational tool-aided structure prediction and integrating various data (sample taxonomy, antiproliferative activity, and compound identity) into a molecular network, a total of 11 indole alkaloids and 47 types of quinolone alkaloids were successfully annotated and visualized into three targeted bioactive molecular families. Within these families, up to 25 types of quinolone alkaloids were found that were previously unreported in TR fruit. Four indole alkaloids and five types of quinolone alkaloids were targeted as potentially antiproliferative compounds in the EtOAc fraction F2-3, and three (evodiamine, dehydroevodiamine, and schinifoline) of these targeted alkaloids can serve as marker compounds of F2-3. Evodiamine was verified to be one of the major antiproliferative compounds, and its structural analogues discovered in the molecular network were found to be promising antitumor agents. These results exemplify the application of an LC-MS/MS-based multi-informative molecular networking strategy in the discovery and annotation of bioactive compounds from complex mixtures of potential functional food ingredients.

Preclinical Drug Pharmacokinetic, Tissue Distribution and Excretion Profiles of the Novel Limonin Derivate HY-071085 as an Anti-Inflammatory and Analgesic Candidate in Rats and Beagle Dogs

Limonin is one of the research hotspots in natural drug development. However, its low solubility in water leads to poor oral bioavailability, discouraging the further study of its potential as a candidate compound. In order to overcome this limitation, and to enhance its biological activities, a novel limonin derivative—HY-071085—was synthesized by structural modification, and has exhibited strong anti-inflammatory and analgesic activity. In order to achieve a thorough understanding of the biological actions of HY-071085 in vivo, this study evaluated the pharmacokinetics and bioavailability of HY-071085 in rats and beagle dogs, and the distribution and excretion in rats. Using ultra-high-performance liquid chromatography-tandem mass spectrometry, the kinetic profiles of HY-071085 in the plasma of healthy rats and beagle dogs after a single gavage, repeated gavages and the intravenous injection of HY-071085 were studied. The tissue distribution (heart, liver, spleen, lung, kidney, gastric tissue, intestine, brain, skin, testis, ovary and womb) and excretion of HY-071085 were also studied. These results showed that HY-071085 has nonlinear dynamic characteristics in rat and beagle dog plasma. It was found that the plasma concentrations of HY-071085 in female rats were significantly higher than those in male rats after a single oral administration. There were gender differences in the kinetic behavior of HY-071085 in rats; however, there was no difference identified in dogs. HY-071085 was mainly eliminated as metabolites in rats, and was distributed in most of the tissues except the brain, with the highest content being in the gastric tissue and intestinal arease, followed by the liver, spleen, fat, lung, kidney, ovary and heart. The bioavailability of HY-071085 in male and female rats was 2.8% and 10.8%, respectively, and was about 13.1% in beagle dogs. The plasma protein binding rate of HY-071085 in rats, beagle dogs and humans ranged from 32.9% to 100%, with obvious species differences. In conclusion, our study provides useful information regarding the absorption, distribution and excretion of HY-071085, which will provide a good base for the study of the mechanism of its biological effects.

Molecular docking study of GSK-3β interaction with nomilin, kihadanin B, and related limonoids and triterpenes with a furyl-δ-lactone core

Glycogen synthase kinase-3β (GSK-3β) is a target enzyme considered for the treatment of multiple human diseases, from neurodegenerative pathologies to viral infections and cancers. Numerous inhibitors of GSK-3β have been discovered but thus far only a few have reached clinical trials and only one drug, tideglusib (1), has been registered. Natural products targeting GSK-3β have been identified, including the two anticancer limonoids obacunone (5) and gedunin (4), both presenting a furyl-δ-lactone core. To help identifying novel GSK-3β ligands, we have performed a molecular docking study with 15 complementary natural products bearing a furyl-δ-lactone unit (such as limonin (6) and kihadanins A (8) and B (9)) or a closely related structure (such as cedrelone (10) and nimbolide (11)). The formation of GSK-3β-binding complexes for those natural products was compared to reference GSK-3β ATP-competitive inhibitors LY2090314 (3) and AR-A014418 (2). Our in silico analysis led to the identification of two new GSK-3β-binding natural products: kihadanin B (9) and nomilin (7). The latter surpassed the reference compounds in terms of calculated empirical energy of interaction (ΔE). Nomilin (7) can possibly bind to the active site of GSK-3β, notably via the furyl-δ-lactone core and its 1-acetyl group, implicated in the protein interaction. Compound structure-binding relationships are discussed. The study should help the discovery of novel natural products targeting GSK-3β.

Antiproliferative Effect of Phellodendron amurense Rupr. Based on Angiogenesis

Phellodendron amurense Rupr. is medicinal plant used for supplemental therapy of various diseases based on their positive biological activities. The aim of this study was evaluated the main metabolite, safety of application and anticancer potential. Berberine was determined by HPLC as main alkaloid. Harmful character was determined by irritation test in ovo. The potential cancerogenic effect was studied in vitro on a cellular level, in ovo by CAM assay and in vivo on whole organism Artemia franciscana. Extract from the bark of Phellodendron amurense showed antiproliferative and antiangiogenic effects. The results of our work showed promising anticancer effects based also on the inhibition of angiogenesis with minimum negative effects.

Limonin Isolated From Pomelo Seed Antagonizes Aβ25-35-Mediated Neuron Injury via PI3K/AKT Signaling Pathway by Regulating Cell Apoptosis

Pomelo seed as a by-product from pomelo consumption is rich in bioactive compounds, however, a huge volume of pomelo seed was disposed as wastes, the comprehensive utilization of pomelo seed could not only generate valued-added products/ingredients, but also decrease the environmental pollution. In this study, the main active substance limonin in pomelo seed was considered as a high-value bioactive compound. The purification of limonin from pomelo seed was investigated, and the neuroprotective and mechanism were characterized. The UPLC-MS/MS results indicated that 29 compounds in pomelo seed were identified, including 14 flavonoids, 3 limonids, 9 phenols and 3 coumarins. Moreover, high purity of limonin was obtained by crystallization and preparative-HPLC. Furthermore, limonin pretreatment can antagonize the cell damage mediated by Aβ₂₅₋₃₅ in a concentration-dependent relationship. The regulation of Bax/Bcl-2, expression of caspase-3 protein and the activation of PI3K/Akt signaling pathway were observed in the cells pretreated with limonin. Treatment of PC12 cells with PI3K inhibitor LY294002 weakened the protective effect of limonin. These results indicated that limonin prevented Aβ₂₅₋₃₅-induced neurotoxicity by activating PI3K/Akt, and further inhibiting caspase-3 and up-regulating Bcl-2. This study enables comprehensive utilization of pomelo seed as by-product and offers a theoretical principle for a waste-to-wealth solution, such as potential health benefits of food ingredient and drug.

Limonin relieves TGF-β-induced hepatocyte EMT and hepatic stellate cell activation in vitro and CCl4-induced liver fibrosis in mice via upregulating Smad7 and subsequent suppression of TGF-β/Smad cascade

Liver fibrosis is a pathological process as a result of intrahepatic deposition of excessive extracellular matrix. Epithelial-mesenchymal transition (EMT) of hepatocytes and activation of hepatic stellate cells (HSCs) both play important roles in the etiology of liver fibrosis. Here, we found that limonin repressed transforming growth factor-β1 (TGF-β)-induced EMT in AML-12 hepatocytes and activation of LX-2 HSCs. In both kinds of cells, limonin suppressed TGF-β-provoked Smad2/3 C-terminal phosphorylation and subsequent nuclear translocation. Transcription of Smad2/3-downstream genes was in turn reduced. However, limonin exerted few effects on Smad2/3 phosphorylation at linker region. Mechanistically, limonin increased Smad7 at mRNA level in both AML-12 and LX-2 cells. Knockdown of Smad7 abrogated inhibitory effects of limonin on TGF-β-induced EMT in AML-12 cells and activation of LX-2 cells. Further studies revealed that limonin alleviated mouse liver fibrosis induced by CCl₄. In livers of model mice, limonin upregulated Smad7 and declined C-terminal phosphorylation and nuclear translocation of Smad2/3. Transcription of Smad2/3-responsive genes was also attenuated. Our findings indicated that limonin inhibits TGF-β-induced EMT of hepatocytes and activation of HSCs in vitro and CCl₄-induced liver fibrosis in mice. Upregulated Smad7 which suppresses Smad2/3-dependent gene transcription is implicated in the hepatoprotective activity of limonin.

Computational studies on the interaction of SARS-CoV-2 Omicron SGp RBD with human receptor ACE2, limonin and glycyrrhizic acid

On November 24, 2021, the SARS-CoV-2 Omicron variant (B.1.1.529) was first identified in South Africa. The World Health Organization (WHO) declared the Omicron as a variant of concern (VoC) because of the unexpected and large numbers of mutations occurred in the genome, higher viral transmission and immune evasions. The present study was performed to explore the interactions of SARS-CoV-2 spike glycoprotein receptor-binding domain (SGp RBD) of the three variants (Omicron, Delta, and WT) with the receptor hACE2. The structural changes occurred in Omicron due to the mutations at key positions improved the ability to mediate SARS-CoV-2 viral infection compared to other VoCs. The phytochemicals limonin and glycyrrhizic acid were docked with the SGp RBD of the variants WT, Delta and Omicron. The computed dock score revealed that limonin and glycyrrhizic acid binds effectively at the SGp RBD of all three variants, and showed almost similar binding affinity at the binding interface of ACE2. Therefore, despite the multiple mutations occurred in Omicron and its viral transmission is comparatively high, the computed binding affinity of the phytochemicals limonin and glycyrrhizic acid supported that the traditional medicines can be useful in formulating adjuvant therapies to fight against the SARS-CoV-2 Omicron.

A Green Extraction Method to Achieve the Highest Yield of Limonin and Hesperidin from Lime Peel Powder (Citrus aurantifolia)

Green extraction is aimed at reducing energy consumption by using renewable plant sources and environmentally friendly bio-solvents. Lime (Citrus aurantifolia) is a rich source of flavonoids (e.g., hesperidin) and limonoids (e.g., limonin). Manufacturing of lime products (e.g., lime juice) yields a considerable amount of lime peel as food waste that should be comprehensively exploited. The aim of this study was to develop a green and simple extraction method to acquire the highest yield of both limonin and hesperidin from the lime peel. The study method included ethanolic-aqueous extraction and variable factors, i.e., ethanol concentrations, pH values of solvent, and extraction temperature. The response surface methodology was used to optimize extraction conditions. The concentrations of limonin and hesperidin were determined by using UHPLC-MS/MS. Results showed that the yields of limonin and hesperidin significantly depended on ethanol concentrations and extraction temperature, while pH value had the least effect. The optimal extraction condition with the highest amounts of limonin and hesperidin was 80% ethanol at pH 7, 50 °C, which yields 2.072 and 3.353 mg/g of limonin and hesperidin, respectively. This study illustrates a green extraction process using food waste, e.g., lime peel, as an energy-saving source and ethanol as a bio-solvent to achieve the highest amount of double bioactive compounds.

Limonin, an AMPK Activator, Inhibits Hepatic Lipid Accumulation in High Fat Diet Fed Mice

NAFLD is the most prevalent liver disease in human history. The treatment is still limited yet. In the current study, we reported that limonin inhibited hepatic lipid accumulation and fatty acid synthesis in HFD fed mice. Using AMPK inhibitor and AMPK deficient C. elegans, we revealed the effect was dependent on the activation of AMPK. We found that limonin activated AMPK through inhibition of cellular energy metabolism and increasing ADP:ATP ratio. Furthermore, the treatment of limonin induced AMPK mediated suppression of the transcriptional activity of SREBP1/2. Our study suggests that limonin may a promising therapeutic agent for the treatment of NAFLD.

Separation and Enrichment of Alkaloids from Coptidis Rhizoma and Euodiae Fructus by Macroporous Resin and Evaluation of the Effect on Bile Reflux Gastritis Rats

The Zuojin Pill consists of Coptidis Rhizoma (CR) and Euodiae Fructus (EF). It has been a classic prescription for the treatment of gastrointestinal diseases in China since ancient times. Alkaloids are considered to be its main pharmacologically active substances. The authors of the present study investigated the feasibility of preparing high purity total alkaloids (TAs) from CR and EF extracts separately and evaluated the effect for the treatment of bile reflux gastritis (BRG). Coptis chinensis Franch. and Evodia rutaecarpa (Juss.) Benth. were used in the study. An optimized method for the enrichment and purification of TAs with macroporous resin was established. Furthermore, qualitative analysis by using ultra-high performance liquid chromatography coupled with electrospray ionization and quadrupole-time of flight mass spectrometry (UHPLC–ESI–QTOF-MS) was explored to identify the components of purified TAs. Thirty-one compounds, thirty alkaloids and one phenolic compound, were identified or tentatively assigned by comparison with reference standards or literature data. A method of ultra-high performance liquid chromatography coupled with diode array detector (UHPLC–DAD) for quantitative analysis was also developed. The contents of nine alkaloids were determined. Moreover, a rat model of BRG was used to investigate the therapeutic effect of the combination of purified TAs from CR and EF. Gastric pathologic examination suggested that the alkaloids’ combination could markedly attenuate the pathological changes of gastric mucosa.

Limonin Alleviates Non-alcoholic Fatty Liver Disease by Reducing Lipid Accumulation, Suppressing Inflammation and Oxidative Stress

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease and continues to rise in the worldwide. Limonin is a triterpenoid compound widely found in the fruits of citrus plants with a wide range of pharmacological effects, including anti-cancer, anti-inflammation, anti-viral, anti-oxidation and liver protection properties. However, the potential molecular mechanism of limonin on NAFLD in zebrafish remains unknown. In this study, zebrafish larvae were exposed to thioacetamide to establish an NAFLD model and the larvae were treated with limonin for 72 h simultaneously. The human liver cell line was stimulated with lipid mixture and meanwhile incubated with limonin for 24 h. The results showed that Limonin significantly reduced the accumulation of lipid droplets in the liver and down-regulated the levels of lipogenic transcription factors FASN and SREBP1 in NAFLD. Limonin suppressed macrophages infiltration and the down-regulated the relative expression levels of the pro-inflammatory factors IL-6, IL-1β and TNF-α secreted by macrophages. Besides, limonin could reversed the reduction of glutathione and the accumulation of reactive oxygen species through up-regulating NRF2/HO-1 signaling pathway in the liver. In conclusion, this study revealed that limonin has a protective effect on NAFLD due to its resistance to lipid deposition as well as antioxidant and anti-inflammatory actions.

Evolving Roles of Natural Terpenoids From Traditional Chinese Medicine in the Treatment of Osteoporosis

Osteoporosis (OP) is a systemic metabolic skeletal disease which can lead to reduction in bone mass and increased risk of bone fracture due to the microstructural degradation. Traditional Chinese medicine (TCM) has been applied in the prevention and treatment of osteoporosis for a long time. Terpenoids, a class of natural products that are rich in TCM, have been widely studied for their therapeutic efficacy on bone resorption, osteogenesis, and concomitant inflammation. Terpenoids can be classified in four categories by structures, monoterpenoids, sesquiterpenoids, diterpenoids, and triterpenoids. In this review, we comprehensively summarize all the currently known TCM-derived terpenoids in the treatment of OP. In addition, we discuss the possible mechanistic-of-actions of all four category terpenoids in anti-OP and assess their therapeutic potential for OP treatment.

Exploring the therapeutic nature of limonoids and triterpenoids against SARS-CoV-2 by targeting nsp13, nsp14, and nsp15 through molecular docking and dynamic simulations

Background and aim

The ongoing global pandemic due to SARS-CoV-2 caused a medical emergency. Since December 2019, the COVID-19 disease is spread across the globe through physical contact and respiratory droplets. Coronavirus caused a severe effect on the human immune system where some of the non-structural proteins (nsp) are involved in virus-mediated immune response and pathogenesis. To suppress the viral RNA replication mechanism and immune-mediated responses, we aimed to identify limonoids and triterpenoids as antagonists by targeting helicases (nsp13), exonuclease (nsp14), and endoribonuclease (nsp15) of SARS-CoV-2 as therapeutic proteins.

Experimental procedure

In silico molecular docking and drug-likeness of a library of 369 phytochemicals from limonoids and triterpenoids were performed to screen the potential hits that binds effectively at the active site of the proteins target. In addition, the molecular dynamics simulations of the proteins and their complexes with the potential hits were performed for 100 ns by using GROMACS.

Results and conclusion

The potential compounds 26-deoxyactein and 25-O-anhydrocimigenol 3-O-beta-d-xylopyranoside posing strong interactions with a minimum binding energy of -10.1 and -9.5 kcal/mol, respectively and sustained close contact with nsp13 for 100 ns. The nsp14 replication fork activity was hindered by the tomentosolic acid, timosaponin A-I, and shizukaol A with the binding affinity score of -9.2, -9.2, and -9.0 kcal/mol, respectively. The nsp15 endoribonuclease catalytic residues were inhibited potentially by limonin, 25-O-anhydrocimigenol 3-O-alpha-l-arabinopyranoside, and asperagenin posing strong binding affinity scores of -9.0, -8.8, and -8.7 kcal/mol, respectively. Computationally predicted potential phytochemicals for SARS-CoV-2 are known to possess various medicinal properties.

Limonin ameliorates acute pancreatitis by suppressing JAK2/STAT3 signaling pathway

Acute pancreatitis (AP) is one of the most common acute abdomen of digestive system and has the characteristics of dangerous condition and rapid development. Limonin has been confirmed to hold anti-inflammatory and antioxidant effects in various diseases. However, its potential beneficial effect on AP and the concrete mechanisms have never been revealed. Here, two mouse models were used to investigate the protective effects of limonin on AP, the caerulein-induced mild acute pancreatitis (MAP) model and L-arginine-induced severe AP (SAP) model. Firstly, it was found that limonin administration attenuated lipase and serum amylase levels and ameliorated the histopathological manifestations of pancreatic tissue in a dose-dependent manner. Additionally, the amelioration of AP by limonin was associated with reduced levels of inflammation initiators (IL-6, IL-1β, CCL2, and TNF-α). Mechanistically, we found that limonin suppressed the Janus Activating Kinase 2 (JAK2)/Signal Transducer and Activator of Transcription 3 (STAT3) signaling pathway, as evident by the decreased levels of JAK2 and p-STAT3. And activation of JAK2 using JAK2 activator rescued the protective effects of limonin on AP. Thus, our results demonstrate that limonin can ameliorate AP in two mice models via suppressing JAK2/STAT3 signaling pathway.

Design, Synthesis, and In Vitro and In Vivo Biological Evaluation of Limonin Derivatives for Anti-Inflammation Therapy

In this study, limonin derivatives were used to design new anti-inflammatory compounds with high pharmacological activity and low toxicity. A total of 23 new limonin derivatives were discovered, synthesized, and screened for their anti-inflammatory activity against lipopolysaccharide (LPS)-treated RAW 264.7 cells. Of them, compound f4 was found to be the most active, with a higher efficiency compared with limonin and celecoxib. Subsequently, we studied the mechanism underlying the activity of f4 and found that it inhibited proinflammatory cytokines by blocking the NF-κB/MAPK signaling pathway in LPS-treated RAW 264.7 cells as well as mice. In conclusion, f4 may be a promising anti-inflammatory lead compound.

Antioxidant Activity of Citrus Limonoids and Investigation of Their Virucidal Potential against SARS-CoV-2 in Cellular Models

The COVID-19 pandemic represents an unprecedented global emergency. Despite all efforts, COVID-19 remains a threat to public health, due to the complexity of mass vaccination programs, the lack of effective drugs, and the emergence of new variants. A link has recently been found between the risk of developing a severe COVID-19 infection and a high level of oxidative stress. In this context, we have focused our attention on natural compounds with the aim of finding molecules capable of acting through a dual virucidal–antioxidant mechanism. In particular, we studied the potential of grapefruit seed extracts (GSE) and their main components, belonging to the class of limonoids. Using chemical and biological approaches including isolation and purification of GSE, antioxidant and virucidal assays, we have shown that grapefruit seed constituents, belonging to the class of limonoids, are endowed with remarkable virucidal, antioxidant and mitoprotective activity.

Phytochemical and Therapeutic Potential of Citrus grandis (L.) Osbeck: A Review

Citrus grandis or Citrus maxima, widely recognized as Pomelo is widely cultivated in many countries because of their large amounts of functional, nutraceutical and biological activities. In traditional medicine, various parts of this plant including leaf, pulp and peel are used for generations as they are scientifically proven to have therapeutic potentials and safe for human use. The main objective of this study was to review the different therapeutic applications of Citrus grandis and the phytochemicals associated with its medicinal values. In this article different pharmacological properties like antimicrobial, antitumor, antioxidant, anti-inflammatory, anticancer, antiepileptic, stomach tonic, cardiac stimulant, cytotoxic, hepatoprotective, nephroprotective, and anti-diabetic activities of the plant are highlighted. The enrichment of the fruit with flavonoids, polyphenols, coumarins, limonoids, acridone alkaloids, essential oils and vitamins mainly helps in exhibiting the pharmacological activities within the body. The vitamins enriched fruit is rich in nutritional value and also has minerals like calcium, phosphorous, sodium and potassium, which helps in maintaining the proper health and growth of the bones as well as the electrolyte balance of the body. To conclude, various potential therapeutic effects of Citrus grandis have been demonstrated in recent literature. Further studies on various parts of fruit, including pulp, peel, leaf, seed and it essential oil could unveil additional pharmacological activities which can be beneficial to the mankind.