Uptake and Transport Mechanism of Dihydromyricetin Across Human Intestinal Caco-2 Cells

Quercetin Enhances the Availability of 5-Heptadecylresorcinol by Inhibiting the Expression of P-gp

5-Heptadecylresorcinol (AR-C17), as the most important active monomer, is found in large quantities in wheat and triticale and plays a variety of health benefits, such as antidiabetic, anti-inflammatory, and antitumor. However, the low bioavailability of AR-C17 due to its low water solubility restricts its application. Moreover, the transport mechanism of AR-C17 is not fully understood. Here, we showed that the transport of AR-C17 in vitro was time- and concentration-dependent, and relatively higher temperature and lower pH obviously promoted the transport of AR-C17. Besides, transporters, especially P-glycoprotein (P-gp), markedly affected the transport of AR-C17 as well. Quercetin, a natural synergist in triticale bran (TB), was confirmed as an inhibitor of P-gp to promote the transport of AR-C17 in this study, and the bioavailability of AR-C17 reached the highest when the concentration ratio of quercetin to AR-C17 was 1:1.

Impact of dietary plant flavonoids on 7,8-dihydroxyflavone transepithelial transport in human intestinal Caco-2 cells

7,8-dihydroxyflavone (7,8-DHF) is a biologically active flavone with various physiological activities, including neuroprotection, anti-inflammation, and weight loss. Previous studies have found that the efflux protein P-glycoprotein (P-gp) significantly affects the transepithelial transport of 7,8-DHF in the intestine, resulting in its low oral bioavailability. Based on this, in this study, a Caco-2 monolayer cell model was used to investigate 14 dietary plant flavonoids as potential P-gp inhibitors, and their effects on the transepithelial transport and in vitro digestion of 7,8-DHF were explored. The results showed that among the 14 plant flavonoids, hesperetin, epigallocatechin gallate, fisetin, kaempferol, quercetin, and isoorientin increased and the apparent permeability coefficients (P app) of 7,8-DHF at AP → BL direction and lowered P app value at BL → AP direction to varying degrees, reducing the efflux ratio of 7,8-DHF less than 1.5. In particular, kaempferol and quercetin exhibited the best effect on promoting the transepithelial transport of 7,8-DHF, especially when used at molar concentration ratios of 1:1 and 1:2 with 7,8-DHF. This is beneficial for improving the oral bioavailability of 7,8-DHF. Meanwhile, 7,8-DHF was found to maintain structural stability in simulated saliva, gastric juice, and intestinal juice, and its stability was not affected by the coexistence of quercetin and kaempferol. Overall, this study provided a theoretical basis for seeking natural and safe P-gp inhibitors to improve the oral absorption of natural products.

Preparation, characterization and protective effect of chitosan - Tripolyphosphate encapsulated dihydromyricetin nanoparticles on acute kidney injury caused by cisplatin

Dihydromyricetin (DMY) is a natural dihydroflavonol compound known for its diverse pharmacological benefits. However, its limited stability and bioavailability posed significant challenges for further applications. To address these issues, in this study, an ion crosslinking method was utilized to prepare chitosan nanoparticles that were loaded with DMY. The synthesized chitosan nanoparticles (CS-DMY-NPs) were spherical in shape with particle size and ζ potential of 198.7 nm and 45.05 mV, respectively. Furthermore, in vitro release experiments demonstrated that CS-DMY-NPs had sustained release and protective effects in simulated gastric and intestinal fluids. CS-DMY-NPs exhibited better antioxidant activity by ABTS and DPPH radical scavenging activity than free DMY. In vivo study showed that CS-DMY-NPs alleviated cisplatin-induced kidney damage by inhibiting oxidative stress and proinflammatory cytokines, and had better activity compared to DMY (free). Immunofluorescence data showed that CS-DMY-NPs activated the Nrf2 signaling pathways in a dose-dependent manner to combat cisplatin-induced kidney damage. Our results demonstrate that CS-TPP has good compatibility with DMY, and CS-DMY-NPs exhibited better protective effects against cisplatin-induced acute kidney injury (AKI) than free DMY.

An efficient cocrystallization strategy for separation of dihydromyricetin from vine tea and enhanced its antibacterial activity for food preserving application

The objective of this study was to optimize the separation and purification of dihydromyricetin (DMY) from vine tea to obtain high purity, antibacterial and antioxidant crystal forms. We developed a cocrystallization approach for separation of DMY from vine tea with easy operation and high efficiency. The type and concentration of co-formers as well as solvent for separation have been investigated in detail. Under the optimal conditions, DMY with a purity of 92.41% and its two co-crystal forms (purity >97%) can be obtained. Three DMY crystal forms had consistent and good antioxidant activities according to DPPH radical scavenging results. DMY had effective antibacterial activity against the two kinds of drug-resistant bacteria including CRAB and MRSA, and DMY co-crystals had a greater advantage than DMY itself on CRAB. This work implies that cocrystallization can be used for the DMY separation and enhanced its anti-drug-resistant bacteria activity in food preservation.

Chemical profiling and cytotoxic potential of the n-butanol fraction of Tamarix nilotica flowers

BACKGROUND

Cancer represents one of the biggest healthcare issues confronting humans and one of the big challenges for scientists in trials to dig into our nature for new remedies or to develop old ones with fewer side effects. Halophytes are widely distributed worldwide in areas of harsh conditions in dunes, and inland deserts, where, to cope with those conditions they synthesize important secondary metabolites highly valued in the medical field. Several Tamarix species are halophytic including T.nilotica which is native to Egypt, with a long history in its tradition, found in its papyri and in folk medicine to treat various ailments.

METHODS

LC-LTQ-MS-MS analysis and ¹H-NMR were used to identify the main phytoconstituents in the n- butanol fraction of T.nilotica flowers. The extract was tested  in vitro for its cytotoxic effect against breast (MCF-7) and liver cell carcinoma (Huh-7) using SRB assay.

RESULTS

T.nilotica n-butanol fraction of the flowers was found to be rich in phenolic content, where, LC-LTQ-MS-MS allowed the tentative identification of thirty-nine metabolites, based on the exact mass, the observed spectra fragmentation patterns, and the literature data, varying between tannins, phenolic acids, and flavonoids. ¹H-NMR confirmed the classes tentatively identified. The in-vitro evaluation of the n-butanol fraction showed lower activity on MCF-7 cell lines with IC₅₀ > 100 µg/mL, while the higher promising effect was against Huh-7 cell lines with an IC₅₀= 37 µg/mL.

CONCLUSION

Our study suggested that T.nilotica flowers' n-butanol fraction is representing a promising cytotoxic candidate against liver cell carcinoma having potential phytoconstituents with variable targets and signaling pathways.

Dihydromyricetin attenuates intracerebral hemorrhage by reversing the effect of LCN2 via the system Xc- pathway

BACKGROUND

The limited understanding of the pathological mechanisms of intracerebral hemorrhage (ICH) and the absence of successful therapies lead to poor prognoses for patients with ICH. Dihydromyricetin (DMY) has many physiological functions, such as regulating lipid and glucose metabolism and modulating tumorigenesis. Moreover, DMY has been proven to be an effective treatment of neuroprotection. However, no reports to date have been made regarding the impact of DMY on ICH.

PURPOSE

This investigation aimed to identify the role of DMY on ICH in mice and the underlying mechanisms.

METHODS/RESULTS

This study demonstrated that DMY treatment effectively reduced hematoma size and cell apoptosis of brain tissue, and improved neurobehavioral outcomes in mice with ICH. Transcriptional and network pharmacological analyses revealed that lipocalin-2 (LCN2) was a potential target of DMY in ICH. After ICH, LCN2 mRNA and protein expression in brain tissue increased and DMY could inhibit the expression of LCN2. The rescue experiment with the implementation of LCN2 overexpression verified these observations. Furthermore, after DMY treatment, there was a significant decrease in cyclooxygenase 2 (COX2), phospho-extracellular regulated protein kinase (P-ERK), iron deposition, and the number of abnormal mitochondria, which were reversed by the overexpression of LCN2. Proteomics analysis suggests that SLC3A2 may be the downstream target of LCN2, promoting ferroptosis. Finally, LCN2 was shown to bind to SLC3A2 and regulate the downstream glutathione (GSH) synthesis and Glutathione Peroxidase 4 (GPX4) expression and glutathione (GSH) synthesis, as determined by molecular docking and co-immunoprecipitation analysis.

CONCLUSION

Our study confirmed for the first time that DMY might offer a favorable treatment for ICH through its action on LCN2. The possible mechanism for this could be that DMY reverses the inhibitory effect of LCN2 on the system Xc-, lessening ferroptosis in brain tissue. The findings of this study offer a greater understanding of how DMY affects ICH at a molecular level and could be conducive to developing therapeutic targets for ICH.

Molecular mechanisms and promising role of dihydromyricetin in cardiovascular diseases

Vine tea, a Chinese herbal medicine, is widely used in traditional Asian medicine to treat common health problems. Dihydromyricetin (DMY) is the main functional flavonoid compound extracted from vine tea. In recent years, preclinical studies have focused on the potential beneficial effects of dihydromyricetin, including glucose metabolism regulation, lipid metabolism regulation, neuroprotection, and anti-tumor effects. In addition, DMY may play a role in cardiovascular disease by resisting oxidative stress and participating in the regulation of inflammation. This review is the first review that summaries the applications of dihydromyricetin in cardiovascular diseases, including atherosclerosis, myocardial infarction, myocardial hypertrophy, and diabetic cardiomyopathy. We also clarified the underlying mechanisms and signaling pathways involved in the above process. The aim of this review is to provide a better understanding and quick overview for future researches of dihydromyricetin in the field of cardiovascular diseases, and more detailed and robust researches are needed for evaluation and reference.

Ampelopsin targets in cellular processes of cancer: Recent trends and advances

Cancer is being considered as a serious threat to human health globally due to limited availability and efficacy of therapeutics. In addition, existing chemotherapeutic drugs possess a diverse range of toxic side effects. Therefore, more research is welcomed to investigate the chemo-preventive action of plant-based metabolites. Ampelopsin (dihydromyricetin) is one among the biologically active plant-based chemicals with promising anti-cancer actions. It modulates the expression of various cellular molecules that are involved in cancer progressions. For instance, ampelopsin enhances the expression of apoptosis inducing proteins. It regulates the expression of angiogenic and metastatic proteins to inhibit tumor growth. Expression of inflammatory markers has also been found to be suppressed by ampelopsin in cancer cells. The present review article describes various anti-tumor cellular targets of ampelopsin at a single podium which will help the researchers to understand mechanistic insight of this phytochemical.

Present Status, Challenges, and Prospects of Dihydromyricetin in the Battle against Cancer

Dihydromyricetin (DHM) is a natural flavonoid compound extracted from Ampelopsis grossedentata that has been used for centuries in traditional Chinese medicine. DHM has attracted intensive attention due to its numerous beneficial activities, such as hepatoprotection, cardioprotection, antioxidant, and anti-inflammation. In addition, DHM inhibits the progression of cancers such as lung cancer, hepatocellular cancer, breast cancer, melanoma, and malignant reproductive systems through multiple mechanisms, including antiangiogenesis, antiproliferation, apoptosis, and inhibition of invasion and migration. Notably, DHM also activates autophagy at different levels, exerting a dual-regulatory effect on cancers. Mechanistically, DHM can effectively regulate mammalian target of rapamycin (mTOR), noncoding RNA-mediated signaling, phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway, nuclear factor-κB (NF-κB), p53, and endoplasmic reticulum stress (ER stress)-driven signaling in different types of cancers. DHM has also been shown to have inhibitory effects on various regulators that trigger epithelial–mesenchymal transition (EMT). Furthermore, DHM exhibits a remarkable anticancer reversal ability when used in combination with drugs such as adriamycin, nedaplatin, and other drugs. However, the low bioavailability of DHM limits its potential applications, which are improved through structural modification and the exploration of novel dosage forms. Therefore, DHM may become a promising candidate for treating malignancies alone or combined with conventional anticancer strategies used in clinical practice.

Investigation of the Uptake and Transport of Aspirin Eugenol Ester in the Caco-2 Cell Model

Background: Aspirin eugenol ester (AEE) is a novel medicinal compound synthesized by esterification of aspirin with eugenol using the prodrug principle. AEE has the pharmacological activities of being anti-inflammatory, antipyretic, analgesic, anti-cardiovascular diseases, and anti-oxidative stress However, its oral bioavailability is poor, and its intestinal absorption and transport characteristics are still unknown.

Objective: The purpose of this study was to investigate the uptake and transport mechanisms of AEE in Caco-2 cells.

Methods: The effects of time, concentration, and temperature on the transport and uptake of AEE were studied.

Results: The results showed that a higher concentration of salicylic acid (SA) was detected in the supernatant of cell lysates and cell culture medium, while AEE was not detected. Therefore, the content change of AEE was expressed as the content change of its metabolite SA. In the uptake experiment, when the factors of time, concentration, and temperature were examined, the uptake of SA reached the maximum level within 30 min, and there was concentration dependence. In addition, low temperature (4°C) could significantly reduce the uptake of SA in Caco-2 cells. In the transport experiment, under the consideration of time, concentration, and temperature, the transepithelial transport of SA from AP-BL and BL-AP sides was time-dependent. The amount of SA transported in Caco-2 cells increased with the increase of concentration, but the transmembrane transport rate had no correlation with the concentration. This phenomenon may be due to the saturation phenomenon of high concentration. The efflux ratio (ER) was less than 1, which indicated that their intestinal transport mechanism was passive transport. Moreover, the temperature had a significant effect on the transport of AEE.

Conclusion: In summary, intestinal absorption of AEE through Caco-2 cell monolayers was related to passive transport. The uptake and transport of AEE were concentration-dependent, and temperature significantly affected their uptake and transport. The absorption and transport characteristics of AEE may contribute to the exploration of mechanisms of absorption and transport of chemosynthetic drugs in vitro.

Recent update on application of dihydromyricetin in metabolic related diseases

As a new type of natural flavonoids, dihydromyricetin (DMY) has attracted more and more attention. It has a series of pharmacological effects, such as anti-inflammatory, anti-tumor, anti-oxidation, antibacterial and so on, and it is almost no toxicity and with excellent safety. Therefore, even if the bioavailability is poor, it is often added to daily food, beverages and even medicines. In recent years, some researchers have found that DMY can treat some diseases by anti-oxidation, anti-inflammation, promoting cell death and regulate the activity of lipid and glucose metabolism. In addition, the mechanism of DMY on these diseases was also related to the signal pathway of AMPK, PI3K/Akt, PPAR and the participation of microRNAs. This review describes the mechanism of DMY in metabolic related diseases from three aspects: metabolic diseases, liver diseases, and cancers, hoping to provide some new ideas for clinical researches.

Mechanism of Dihydromyricetin on Inflammatory Diseases

Inflammation plays a crucial role in a variety of diseases, including diabetes, arthritis, asthma, Alzheimer’s disease (AD), acute cerebral stroke, cancer, hypertension, and myocardial ischemia. Therefore, we need to solve the problem urgently for the study of inflammation-related diseases. Dihydromyricetin (DHM) is a flavonoid mainly derived from Nekemias grossedentata (Hand.-Mazz.) J.Wen and Z.L.Nie (N.grossedentata). DHM possesses many pharmacological effects, including anti-inflammatory (NLRP-3, NF-κB, cytokines, and neuroinflammation), antioxidant, improving mitochondrial dysfunction, and regulating autophagy and so on. In this review, we consulted the studies in the recent 20 years and summarized the mechanism of DHM in inflammation-related diseases. In addition, we also introduced the source, chemical structure, chemical properties, and toxicity of DHM in this review. We aim to deepen our understanding of DHM on inflammation-related diseases, clarify the relevant molecular mechanisms, and find out the problems and solutions that need to be solved urgently. Providing new ideas for DHM drug research and development, as well as broaden the horizons of clinical treatment of inflammation-related diseases in this review. Moreover, the failure of clinical transformation of DHM poses a great challenge for DHM as an inflammation related disease.

A multifaceted review on dihydromyricetin resources, extraction, bioavailability, biotransformation, bioactivities, and food applications with future perspectives to maximize its value

Natural bioactive compounds present a better alternative to prevent and treat chronic diseases owing to their lower toxicity and abundant resources. (+)-Dihydromyricetin (DMY) is a flavanonol, possessing numerous interesting bioactivities with abundant resources. This review provides a comprehensive overview of the recent advances in DMY natural resources, stereoisomerism, physicochemical properties, extraction, biosynthesis, pharmacokinetics, and biotransformation. Stereoisomerism of DMY should be considered for better indication of its efficacy. Biotechnological approach presents a potential tool for the production of DMY using microbial cell factories. DMY high instability is related to its powerful antioxidant capacity due to pyrogallol moiety in ring B, and whether preparation of other analogues could demonstrate improved properties. DMY demonstrates poor bioavailability based on its low solubility and permeability with several attempts to improve its pharmacokinetics and efficacy. DMY possesses various pharmacological effects, which have been proven by many in vitro and in vivo experiments, while clinical trials are rather scarce, with underlying action mechanisms remaining unclear. Consequently, to maximize the usefulness of DMY in nutraceuticals, improvement in bioavailability, and better understanding of its actions mechanisms and drug interactions ought to be examined in the future along with more clinical evidence.

Exposure to High-Altitude Environment is Associated with Drug Transporters Change: miR-873-5p-Mediated Alteration of Function and Expression Levels of Drug Transporters under Hypoxia

Hypoxia is the main characteristic of a high-altitude environment, affect ing drug metabolism. However, so far, the mechanism of miRNA involved in the regulation of drug metabolism and transporters under high-altitude hypoxia is still unclear. This study aims to investigate the function s and expression levels of multidrug resistance protein 1 ( MDR1 ), m ultidrug resistance-associated protein 2 ( MRP2 ), breast cancer resistance protein ( BCRP ) , peptide transport 1 (PEPT1), and organic anion-transporting polypeptides 2B1 (OATP2B1) in rats and Caco-2 cells after exposure to high - altitude hypoxia. The protein and mRNA expression of MDR1 , MRP2, BCRP, PEPT1, and OATP2B1 were determined by Western blot and qPCR. The function s of MDR1 , MRP2, BCRP, PEPT1, and OATP2B1 were evaluated by determining the effective intestinal permeability and a bsorption rate constants of their specific substrates in rats under high-altitude hypoxia , and uptake and transport studies were performed on Caco-2 cells . To screen the miRNA associated with hypoxia, Caco-2 cells were examined by high throughput sequencing . We observed that the miR-873-5p was significantly decreased under hypoxia and might target MDR1 and pregnane X receptor ( PXR). To clarify whether miR-873-5p regulates MDR1 and pregnane X receptor (PXR) under hypoxia, Caco-2 cells were transfected with mimics or inhibitors of miR-873-5p and negative control (NC). The function and expression of drug transporters were found to be significantly increased in rats and Caco-2 cells under hypoxia. We found that miR-873-5p regulated MDR1 and PXR expression. Herein, it is shown that miRNA may affect the expression of drug transporter and nuclear receptor under hypoxia. Significance Statement This study explores if alterations to the microRNAs, induced by high-altitude hypoxia, can be translated to altered drug transporters. Among miRNAs, which show a significant change in a hypoxic environment, miR-873-5p can act on the MDR1 gene; however, there are multiple miRNAs that can act on the PXR. We speculate that the miRNA-PXR-Drug transporter axis is important in the physiological disposition of drugs. The results of this study are anticipated to be helpful for rational pharmaceutical use in high - altitude environments .

Molecular mechanisms and therapeutic implications of dihydromyricetin in liver disease

Recent studies demonstrated that dihydromyricetin (DHM) has prominent therapeutic effects on liver injury and liver cancer. By summarizing the current preclinical in vitro and in vivo studies, the present review examines the preventive and therapeutic effects of DHM on liver disorders as well as its potential mechanisms. Briefly, in both chemical- and alcohol-induced liver injury models, DHM ameliorates hepatocyte necrosis and steatosis while promoting liver regeneration. In addition, DHM can alleviate nonalcoholic fatty liver disease (NAFLD) via regulating lipid/glucose metabolism, probably due to its anti-inflammatory or sirtuins-dependent mechanisms. Furthermore, DHM treatment inhibits cell proliferation, induces apoptosis and autophagy and regulates redox balance in liver cancer cells, thus exhibiting remarkable anti-cancer effects. The pharmacological mechanisms of DHM may be associated with its anti-inflammatory, anti-oxidative and apoptosis-regulatory benefits. With the accumulating interests in utilizing natural products to target common diseases, our work aims to improve the understanding of DHM acting as a novel drug candidate for liver diseases and to accelerate its translation from bench to bedside.

Identification of Dihydromyricetin and Metabolites in Serum and Brain Associated with Acute Anti-Ethanol Intoxicating Effects in Mice

Dihydromyricetin is a natural bioactive flavonoid with unique GABA_A receptor activity with a putative mechanism of action to reduce the intoxication effects of ethanol. Although dihydromyricetin's poor oral bioavailability limits clinical utility, the promise of this mechanism for the treatment of alcohol use disorder warrants further investigation into its specificity and druggable potential. These experiments investigated the bioavailability of dihydromyricetin in the brain and serum associated with acute anti-intoxicating effects in C57BL/6J mice. Dihydromyricetin (50 mg/kg IP) administered 0 or 15-min prior to ethanol (PO 5 g/kg) significantly reduced ethanol-induced loss of righting reflex. Total serum exposures (AUC0_→24) of dihydromyricetin (PO 50 mg/kg) via oral (PO) administration were determined to be 2.5 µM × h (male) and 0.7 µM × h (female), while intraperitoneal (IP) administration led to 23.8-fold and 7.2- increases in AUC0_→24 in male and female mice, respectively. Electrophysiology studies in α5β3γ2 GABA_A receptors expressed in Xenopus oocytes suggest dihydromyricetin (10 µM) potentiates GABAergic activity (+43.2%), and the metabolite 4-O-methyl-dihydromyricetin (10 µM) negatively modulates GABAergic activity (-12.6%). Our results indicate that administration route and sex significantly impact DHM bioavailability in mice, which is limited by poor absorption and rapid clearance. This correlates with the observed short duration of DHM's anti-intoxicating properties and highlights the need for further investigation into mechanism of DHM's potential anti-intoxicating properties.

Dihydromyricetin Acts as a Potential Redox Balance Mediator in Cancer Chemoprevention

Dihydromyricetin (DHM) is a flavonoid extracted from the leaves and stems of the edible plant Ampelopsis grossedentata that has been used for Chinese Traditional Medicine. It has attracted considerable attention from consumers due to its beneficial properties including anticancer, antioxidative, and anti-inflammatory activities. Continuous oxidative stress caused by intracellular redox imbalance can lead to chronic inflammation, which is intimately associated with the initiation, promotion, and progression of cancer. DHM is considered a potential redox regulator for chronic disease prevention, and its biological activities are abundantly evaluated by using diverse cell and animal models. However, clinical investigations are still scanty. This review summarizes the current potential chemopreventive effects of DHM, including its properties such as anticancer, antioxidative, and anti-inflammatory activities, and further discusses the underlying molecular mechanisms of DHM in cancer chemoprevention by targeting redox balance and influencing the gut microbiota.

Investigation of the uptake and transport of polysaccharide from Se-enriched Grifola frondosa in Caco-2 cells model

A variety of beneficial pharmacological activities have been reported for Se-enriched Grifola frondosa polysaccharides. However, little has been reported on its absorption, and its intestinal uptake and transport profiles remain unknown. Based on our previous research, the aim of this study was to investigate its absorption from two aspects - the polysaccharides and selenium of Se-enriched Grifola frondosa polysaccharides (Se-GFP-22) across Caco-2 cells in vitro. The Caco-2 cells monolayer culture model was successfully constructed to study the transport and uptake of Se-GFP-22. The results revealed that the uptake and transport of Se-GFP-22 were time- and concentration- dependent. Transport studies illustrated that Se-GFP-22 could penetrate Caco-2 cells, mainly mediated through the same routes as endocytosis and selenium in the organic selenium (Se-GFP-22) was more easily absorbed than that in the inorganic selenium control group (sodium selenite). The uptake of Se-GFP-22 may be a macropinocytosis pathway, which was an accumulation from cytoplasm to nucleus process. Se-GFP-22 was a moderately absorbed biological macromolecule testified by the apparent permeability coefficients (Papp) value and transport rates. This work illustrates the characteristics on uptake and transport of Se-GFP-22 and all these results may help to explore the mechanism of polysaccharide absorption in vitro.

Preclinical Research of Dihydromyricetin for Brain Aging and Neurodegenerative Diseases

Brain aging and neurodegenerative diseases share the hallmarks of slow and progressive loss of neuronal cells. Flavonoids, a subgroup of polyphenols, are broadly present in food and beverage and numerous studies have suggested that it could be useful for preventing or treating neurodegenerative diseases in humans. Dihydromyricetin (DHM) is one of the main flavonoids of some Asian medicinal plants that are used to treat diverse illness. The effects of DHM have been studied in different in vitro systems of oxidative damage and neuroinflammation, as well as in animal models of several neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. Here we analyzed the most important effects of DHM, including its antioxidant, anti-inflammatory, and neuroprotective effects, as well as its ability to restore GABA neurotransmission and improve motor and cognitive behavior. We propose new areas of research that might contribute to a better understanding of the mechanism of action of this flavonoid, which could help develop a new therapy for aging and age-related brain diseases.

Dihydromyricetin: A review on identification and quantification methods, biological activities, chemical stability, metabolism and approaches to enhance its bioavailability

BACKGROUND

Dihydromyricetin (DMY) is an important plant flavonoid, which has received great attention due to its health-benefiting activities, including antioxidant, antimicrobial, anti-inflammatory, anticancer, antidiabetic and neuroprotective activities. DMY capsules have been sold in US as a nutraceutical supplement to prevent alcoholic hangovers. The major disadvantage associated with DMY is its chemical instability and poor bioavailability caused by the combined effects of its low solubility and poor membrane permeability. This limits its practical use in the food and pharmaceutical fields.

SCOPE AND APPROACH

The present paper gives an overview of the current methods for the identification and quantification of DMY. Furthermore, recent findings regarding the main biological properties and chemical stability of DMY, the metabolism of DMY as well as different approaches to increase DMY bioavailability in both aqueous and lipid phases are discussed.

KEY FINDINGS AND CONCLUSIONS

Current trends on identification and quantification of DMY have been focused on spectral and chromatographic techniques. Many factors such as heat, pH, metal ions, could affect the chemical stability of DMY. Despite the diverse biological effects of DMY, DMY faces with the problem of poor bioavailability. Utilization of different delivery systems including solid dispersion, nanocapsule, microemuslion, cyclodextrin inclusion complexes, co-crystallization, phospholipid complexes, and chemical or enzymatic acylation has the potential to improve both the solubility and bioavailability. DMY digested in laboratory animals undergoes reduction, dehydroxylation, methylation, glucuronidation, and sulfation. Novel DMY delivery systems and basic pharmacokinetic studies of encapsulated DMY on higher animals and humans might be required in the future.

Gastric floating sustained-release tablet for dihydromyricetin: Development, characterization, and pharmacokinetics study

Dihydromyricetin (DHM) is a natural dihydroflavonol compound with quite a number of important pharmacological properties. However, its low solubility in water and poor stability in aqueous environment, have compromised drug efficacy of DHM, thus hindering its clinical use. The present study was to develop DHM-loaded gastric floating sustained-release tablet (DHM-GFT) to improve the bioavailability of DHM. DHM-GFT was prepared via powder direct compression. The formulation of tablet was optimized in terms of the floating ability and drug release rate. The optimized DHM-GFT exhibited short floating lag time of less than 10 s and long floating duration of over 12 h in acidic medium. It had a 12-hour sustained release of DHM, which proved its potential to develop as a twice-a-day dosing preparation. The physicochemical properties of DHM-GFT well satisfied the pharmacopoeial requirements. In addition, the results from pharmacokinetic studies demonstrated that, DHM-GFT could considerably prolong the in vivo residence time of drug and improve the bioavailability via good gastric floating ability and sustained drug release when compared to DHM powder. Therefore, DHM-GFT is promising to promote the application of DHM and merits studies for further development.

Transepithelial transport mechanisms of 7,8-dihydroxyflavone, a small molecular TrkB receptor agonist, in human intestinal Caco-2 cells

7,8-Dihydroxyflavone (7,8-DHF), as a high-affinity TrkB receptor agonist, has been extensively explored in many human disorders involving brain-derived neurotrophic factor (BDNF) such as Alzheimer's disease, Parkinson's disease, depression, and obesity. However, to date, the transepithelial transport mechanisms of 7,8-DHF in the intestines remain unclear. The aim of our work was to quantify and to characterize in vitro transport of naturally occurring 7,8-DHF distinguished by its physicochemical and pharmacological properties. We discussed the transport mechanisms of 7,8-DHF using the Caco-2 cell model to determine the bi-directional permeability with different environmental factors (time, concentration, pH, metabolic inhibitors etc.). The influx and efflux characteristics of 7,8-DHF were also clarified. 7,8-DHF was poorly transported across Caco-2 cell monolayers by mainly passive diffusion via a transcellular pathway and not a paracellular pathway. The transport of 7,8-DHF was time and concentration-dependent in both the apical (AP) to basolateral (BL) side and the reverse direction. Interestingly, decreasing the pH from 7.4 to 6.0 markedly enhanced 7,8-DHF transport. It is noteworthy that 7,8-DHF transport was strongly inhibited by metabolic inhibitors and was highly dependent on temperature. The efflux ratio (ER) values at different concentrations were all above 1.5, indicating the existence of the efflux transporter. We found that breast cancer resistance protein (BCRP) was not involved in 7,8-DHF secretion and that the transport mechanism of 7,8-DHF was passive transport with an active efflux mediated by P-glycoprotein (P-gp) and multidrug resistance associated proteins (MRPs), particularly MRP 2. Moreover, the use of various influx transporter inhibitors in Caco-2 cells showed that organic cation transporters (OCTs) and organic anion-transporting polypeptides (OATPs) participated in 7,8-DHF transport. Taken together, the elucidated transport characteristics of 7,8-DHF provide useful information for designing novel and efficient delivery systems and avoiding food-food or food-drug interactions.