The high water solubility of inclusion complex of taxifolin-γ-CD prepared and characterized by the emulsion solvent evaporation and the freeze drying combination method

Unveiling the therapeutic potential of Taxifolin in Cancer: From molecular mechanisms to immune modulation and synergistic combinations

BACKGROUND

Taxifolin (TAX), a flavonoid abundant in various medicinal plants, has gained attention for its multifaceted role in cancer therapy and cytoprotection against chemotherapy-induced toxicities. TAX modulates key signaling pathways to regulate several processes within tumors, thus potentially playing an important role in tumor suppression.

PURPOSE

This review aims to explore the current understanding of TAX's role in cancer therapy including its antitumor mechanisms, synergistic combinations, and cytoprotective effects. The review also addresses the safety profile of TAX, highlights its pharmacokinetic (PK) properties limiting its use, and summarizes the suggested pharmaceutical and chemical solutions to overcome these limitations.

METHODOLOGY

A literature review was conducted through searching online databases such as PubMed and Google Scholar using several combinations of relevant keywords related to TAX's potential in anticancer therapy. A total of 84 articles published within the last 15 years were included in this review and analyzed following the PRISMA guidelines.

RESULTS

TAX inhibits tumor proliferation, migration, and invasion via the cGMP-PKG pathway, inducing G1-phase arrest and apoptosis. TAX's anti-angiogenic and pro-apoptotic effects are mediated by downregulating Hif1-α, VEGF, and AKT. Additionally, it can synergize the conventional chemotherapeutic agents, enhancing their efficacy and mitigating drug resistance by inhibiting P-glycoprotein expression. Additionally, TAX demonstrates cytoprotective effects against cisplatin-induced nephrotoxicity and neurotoxicity, cyclophosphamide/pazopanib-induced hepatotoxicity, methotrexate-induced oral mucositis, and doxorubicin-induced cardiotoxicity by inhibiting ferroptosis. TAX further has immunomodulatory effects in the tumor microenvironment, enhancing immune responses and sensitizing tumors to immune checkpoint inhibitors. Advancements in TAX's anticancer effects include introducing novel drug delivery systems and chemical modifications to generate derivatives with improved pharmacological effects.

CONCLUSION

Clinical trials are needed to confirm TAX's safety and effectiveness in cancer therapy, optimize formulations, and investigate synergistic combinations. Overall, TAX holds promise as a versatile anticancer agent, offering direct anticancer effects and protective benefits against chemotherapy-induced toxicities.

Novel aspects of taxifolin pharmacokinetics: Dose proportionality, cumulative effect, metabolism, microemulsion dosage forms

Taxifolin (TFL) is a small drug molecule with a broad therapeutic potential limited by its poor aqueous solubility and excessive metabolism. Despite comprehensive research, some aspects of the TFL pharmacokinetics, e.g., dose proportionality and possible cumulative effect, remain unexplored. In the current study, we have tried to fill this gap. Our results revealed that the TFL pharmacokinetics in rats had nonlinear character in the dose range of 10-50 mg/kg after its single oral administration (AUC). For Cmax, the data are ambiguous: linearity was confirmed via the equivalence criterion and was disproved using the power model approach. Also, the cumulative drug effect was observed on the 4th day after its multiple-dose oral administration (25 mg/kg; compared to the 1st day). Interestingly, biologically active TFL metabolites such as aromadendrin and luteolin were putatively found in plasma samples, although they were previously detected only in feces. In addition, oil-in-water and water-in-oil microemulsions were fabricated to design novel drug delivery systems. These carrier dosage forms did not improve the TFL bioavailability but significantly affected its metabolism. To support pharmacokinetic studies, the bioanalytical liquid chromatography-tandem mass spectrometry method was developed and validated in the concentration range of 1-1000 ng/mL using candesartan as an internal standard. Liquid-liquid extraction with methyl tert-butyl ether was used to isolate the analytes from plasma followed by evaporation and reconstitution of the residues in acetonitrile. Thus, the present findings broaden our understanding of the TFL behavior in vivo and provide novel ideas and reference directions for its continued use in medical practice.

New Perspectives of Taxifolin in Neurodegenerative Diseases

Neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), cerebral amyloid angiopathy (CAA), and Huntington's disease (HD) are characterized by cognitive and motor dysfunctions and neurodegeneration. These diseases have become more severe over time and cannot be cured currently. Until now, most treatments for these diseases are only used to relieve the symptoms. Taxifolin (TAX), 3,5,7,3,4-pentahydroxy flavanone, also named dihydroquercetin, is a compound derived primarily from Douglas fir and Larix gemelini. TAX has been confirmed to exhibit various pharmacological activities, including anti-inflammation, anti-cancer, anti-virus, and regulation of oxidative stress effects. In the central nervous system, TAX has been demonstrated to inhibit Aβ fibril formation, protect neurons and improve cerebral blood flow, cognitive ability, and dyskinesia. At present, TAX is only applied as a health additive in clinical practice. This review aimed to summarize the application of TAX in neurodegenerative diseases and the underlying neuroprotective mechanisms, such as suppressing inflammation, attenuating oxidative stress, preventing Aβ protein formation, maintaining dopamine levels, and thus reducing neuronal loss.

Solubility Enhancement of Dihydroquercetin via "Green" Phase Modification

Dihydroquercetin (DHQ) is a promising antioxidant for medical applications. The poor water solubility of this flavanonol at ambient conditions inhibits its implementation in clinical practice as an injectable dosage form. Thus, increasing water solubility is a critical step toward solving this problem. Herein we attempted to deal with this problem via DHQ phase modification while at the same time adhering to the principles of green chemistry as much as possible. Lyophilization is an appropriate method to achieve phase modification in an environment-friendly way. This method was employed to generate new phase modifications of DHQ that were then characterized. Mixtures of water with ethanol or acetonitrile were used as solvents for the preparation of the lyophilizates, DHQ_E, and DHQ_A, respectively. The results of dissolution testing of the obtained DHQ_E and DHQ_A demonstrated that the lyophilization increased water solubility at least 30-fold times. These new DHQ modifications were studied by scanning electron microscopy, mass-spectrometry, nuclear magnetic resonance spectroscopy, infrared spectroscopy, X-ray powder diffraction, and thermal analysis. Their solid-state phases were confirmed to differ from the initial DHQ substance without any changes in the molecular structure. Both DHQ_E and DHQ_A showed as high antioxidant activity as the initial DHQ. These data demonstrate the potential of DHQ_E and DHQ_A as active pharmaceutical ingredients for injectable dosage forms.

Flavonoids-Based Delivery Systems towards Cancer Therapies

Cancer is the second leading cause of death worldwide. Cervical cancer, for instance, is considered a major scourge in low-income countries. Its development is mostly associated with the human papillomavirus persistent infection and despite the availability of preventive vaccines, they are only widely administered in more developed countries, thus leaving a large percentage of unvaccinated women highly susceptible to this type of cancer. Current treatments are based on invasive techniques, being far from effective. Therefore, the search for novel, advanced and personalized therapeutic approaches is imperative. Flavonoids belong to a group of natural polyphenolic compounds, well recognized for their great anticancer capacity, thus promising to be incorporated in cancer therapy protocols. However, their use is limited due to their low solubility, stability and bioavailability. To surpass these limitations, the encapsulation of flavonoids into delivery systems emerged as a valuable strategy to improve their stability and bioavailability. In this context, the aim of this review is to present the most reliable flavonoids-based delivery systems developed for anticancer therapies and the progress accomplished, with a special focus on cervical cancer therapy. The gathered information revealed the high therapeutic potential of flavonoids and highlights the relevance of delivery systems application, allowing a better understanding for future studies on effective cancer therapy.

Bioavailability and Safety of Dihydroquercetin (Review)

Dihydroquercetin (DHQ) is a bioflavonoid with high antioxidant, capillary-protective, and anti-inflammatory activity. DHQ has previously been used for treating Middle East respiratory syndrome coronavirus (MERS-CoV) infection and is currently considered a potential regulator of oxidative stress as part of COVID-19 multipurpose therapy. DHQ has a high safety profile but low bioavailability that limits its use. Innovative techniques (liposomization, crystal engineering, etc.) can be used to increase its bioavailability.

Comparison of Antioxidant Properties of a Conjugate of Taxifolin with Glyoxylic Acid and Selected Flavonoids

It is known that flavonoids can react with toxic carbonyl compounds in the process of the storage, aging, and digestion of flavonoid-rich foods and beverages. However, the effect of these reactions on the antioxidant properties of the polyphenolic fraction and the properties of the resulting products remain poorly studied. The aim of the present work was to study the antioxidant activity of quercetin, taxifolin, catechin, eriodictyol, hesperetin, naringenin and a product of the condensation of taxifolin with glyoxylic acid, as well as to reveal the structure–activity relationship of these polyphenols. It was found that flavonoids containing the catechol moiety exhibited higher antioxidant activity than hesperetin and naringenin. The product showed the highest hydrogen peroxide scavenging activity, a lower metal-reducing and a higher iron-binding ability than catechol-containing flavonoids, and a lipid peroxidation inhibitory activity comparable with that of taxifolin. Thus, the condensation of flavonoids with toxic carbonyl compounds might lead to the formation of products exhibiting high antioxidant activity. Meanwhile, the conditions under which parent flavonoids and their products exhibit the maximal antioxidant activity may differ. The data suggest that the antioxidant profile of the polyphenolic fraction and bioavailability of polyphenols, carbonyl compounds, and metal ions may change when these reactions occur.

Phenolic compounds: current industrial applications, limitations and future challenges

Phenolic compounds are natural bioactive molecules found mainly in plant tissues that have shown interesting bioactivities, such as antioxidant, antimicrobial, anti-inflammatory, and antiproliferative activities, among others, which has led to great interest in their use by several industries. However, despite the large number of scientific studies on this topic, some issues still need to be studied and solved, such as the understanding of the main actions of these compounds in organisms. Besides their large potential applicability in industry, phenolic compounds still face some issues making it necessary to develop strategies to improve bioavailability, sustainable technologies of extraction and refinement, and stability procedures to increase the range of applicability. This review focuses on the most recent advances in the applications of phenolic compounds in different technological and medicinal areas. In addition, techniques to improve their sustainable resourcing, stability and bioavailability will be presented and discussed.

Solubility and dissolution rate improvement of the inclusion complex of apigenin with 2-hydroxypropyl-β-cyclodextrin prepared using the liquid antisolvent precipitation and solvent removal combination methods

Apigenin (AP) has many pharmacological activities. AP has poor solubility in some solvents. AP is insoluble in water and slightly soluble in ethanol (1.93 mg/ml). It has limited application and exploitation. Therefore, the liquid antisolvent precipitation (LAP) method was applied to improve the solubility of AP in ethanol by changing its crystal form or producing ultra-fine particles. Then, the inclusion complex of AP with 2-Hydroxypropyl-β-cyclodextrin (HP-β-CD) is prepared using the solvent removal method. The effects of various experimental parameters on the solubility of AP in ethanol were investigated through the single factor design. Under the optimum conditions, the AP-ethanol solution of 6.19 mg/ml was obtained. The inclusion complex of AP with HP-β-CD was obtained by the solvent removal method. The load efficiency (LE) and drug encapsulation efficiency (EE) of the inclusion complex of AP with HP-β-CD were 13.98%±0.14% and 97.86%±1.07%, respectively. SEM, FTIR, ¹HNMR, XRD, DSC and TG were used to analyze the characteristics of the inclusion complex of AP with HP-β-CD. These results showed that the inclusion complex has significantly different characteristics with AP. In addition, the dissolution rate and solubility of the inclusion complex were approximately 15.24 and 68.7 times higher than AP in artificial gastric juice, and was separately 10.4 times and 40.05 times higher than AP in artificial intestinal juice. The bioavailability of inclusion complex increased 3.97 times compared with AP.

Synthesis, characterization, solubilization, cytotoxicity and antioxidant activity of aminomethylated dihydroquercetin

A dihydroquercetin derivative (DHQA) was prepared through aminomethylation to overcome the low water solubility and bioavailability of dihydroquercetin (DHQ). DHQA was characterized through HPLC, nuclear magnetic resonance, scanning electron microscopy, X-ray diffraction, and thermogravimetric analyses. DHQA was converted into the amorphous form, but the major structure of DHQ remained unchanged. Solubilization and dissolution tests were also performed. Results showed that the solubility and dissolution rates of DHQA were approximately 16.28 and 6.31 times higher than those of DHQ, respectively. The MTT assay of DHQA showed a non-toxic effect against non-cancerous HEK-293T cells (EC₅₀ = 820.00 μM), and potent inhibitory activity against cancerous Hela cells (EC₅₀ = 138.17 μM). Finally, the antioxidant activity of DHQA was confirmed in vitro through DPPH and ABTS radical scavenging activity assays. DHQA displayed high antioxidant activities with low IC₅₀ values (0.043 and 0.042 mM, respectively). Reducing Fe³⁺ power assay indicated that DHQA exhibited higher reducing power than DHQ and ascorbic acid.

Enhanced dissolution rate and oral bioavailability of ginkgo biloba extract by preparing nanoparticles via emulsion solvent evaporation combined with freeze drying (ESE-FR)

Dissolution rate and oral bioavailability of GBE nanoparticles were significantly improved by emulsion solvent evaporation combined with freeze drying (ESE-FR), implying that ESE-FR has great potential value in the preparation of oral GBE drugs.