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Dihydroquercetin (DHQ) is a representative of flavonoids that is available on the market as a food supplement and registered as an active pharmaceutical ingredient. The structure of this compound is characterized by the presence of two chiral centers in positions 2 and 3 of the pyranone ring. Current regulatory documentation on DHQ lacks quantitative analysis of the stereoisomers of this flavanonol. This poses potential risks for consumers of DHQ-based dietary supplements and developers of new drugs. This review was conducted to systematize data on the pharmacology of DHQ stereoisomers and the possible methods of controlling them in promising chiral drugs. We found that relying on literature data of polarimetry for the identification of DHQ stereoisomers is currently impossible due to these heterogeneities. NMR spectroscopy allows to distinguishing between trans - and cis -DHQ using chemical shifts values. Only HPLC is currently characterized by sufficient enantioselectivity. Regarding pharmacology, the most active stereoisomer of DHQ should be identified, if the substituents in chiral centers both take part in binding with the biological target. The significant impact of stereochemical structure on the pharmacokinetics of DHQ isomers was reported. The question about these toxicity of these compounds remains open. The results of the conducted review of scientific literature indicate the necessity of revising the pharmacology of DHQ taking into account its stereoisomerism., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Terekhov, Savina, Pankov, Korochkina, Taldaev, Yakubovich, Zavadskiy, Zhevlakova and Selivanova.)

Bioavailability is an important biopharmaceutical characteristic of active pharmaceutical ingredients (APIs) that is often correlated with their solubility in water. One of the methods of increasing solubility is freeze drying (lyophilization). The article provides a systematic review of studies published from 2012 to 2022 aimed at optimizing the properties of active pharmaceutical ingredients by freeze drying. This review was carried out in accordance with the recommendations of Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). In general, 141 modifications of 36 APIs attributed to 12 pharmacological groups were reported in selected publications. To characterize the products of phase modification after lyophilization, a complex of analytical methods was used, including microscopic, thermal, X-ray, and spectral approaches. Solubility and pharmacokinetic parameters were assessed. There is a tendency to increase solubility due to the amorphization of APIs during lyophilization. Thus, the alcohol lyophilizate of dihydroquercetin is "soluble" in water compared to the initial substance belonging to the category "very poorly soluble". Based on the analysis of the literature, it can be argued that lyophilization is a promising method for optimizing the properties of APIs.

One of the key factors in the pathogenesis of diabetes and its complications is oxidative stress. To inhibit this process, antioxidants may be helpful. Herein, we focused on the protective properties of taxifolin spheroidal form (TS) in the streptozotocin rat model of diabetes mellitus. After 4 weeks of treatment with TS, the fasting blood glucose level of the diabetic animals decreased by 12% compared with the level right after the injection of streptozotocin. While the feed intake in the untreated diabetic rats increased by 5.3% compared with the healthy group, the TS-treated group showed a pronounced 15.3% decrease. Therapeutic administration of TS has a protective effect on the pancreas and the liver against the cytotoxic action of streptozotocin. The plasma antioxidant capacity of all diabetic groups appeared to be approximately 15% lower than in healthy rats with no significant difference between the TS-treated and untreated diabetic animals. Apparently, this can be attributed to taxifolin and plasma proteins binding. These data demonstrate the potential of TS in antidiabetic therapy.

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.

Wound-healing activity of the crystalline form of dihydroquercetin and its microtubular pseudopolymorphic modification obtained by crystal engineering was compared using the rat model of IIIA degree burn. The rate of wound healing in the group treated with microtubular pseudopolymorphic modification of dihydroquercetin was 4.8±0.1%, which was higher by 11.6% than in the group treated with crystalline form (4.3±0.1%). Bioavailability analysis on MDCK cell culture showed that the apparent permeability coefficient of microtubular pseudopolymorphic modification was higher than that of crystalline form by 31.1% (19.4±0.2×10 -4 and 14.8±0.3×10 -4 cm/sec, respectively). It was proven that the use of crystal engineering improved the biopharmaceutical parameters of dihydroquercetin and increased its pharmacological efficiency.

A large amount of the current literature dedicated to solid states of active pharmaceutical ingredients (APIs) pays special attention to polymorphism of flavonoids. Taxifolin (also known as dihydroquercetin) is an example of a typical flavonoid. Some new forms of taxifolin have been reported previously, however it is still unclear whether they represent polymorphic modifications. In this paper, we tried to answer the question about the taxifolin polymorphism. Taxifolin microtubes and taxifolin microspheres were synthesized from raw taxifolin API using several methods of crystal engineering. All forms were described with the help of spectral methods, scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), and thermal analysis (TA). SEM reveals that the morphology of the solid phase is very specific for each sample. Although XRPD patterns of raw taxifolin and microtubes look similar, their TA profiles differ significantly. At the same time, raw taxifolin and microspheres have nearly identical thermograms, while XRPD shows that the former is a crystalline and the latter is an amorphous substance. Only the use of complex analyses allowed us to put the puzzle together and to confirm the polymorphism of taxifolin. This article demonstrates that taxifolin microtubes are a pseudopolymorphic modification of raw taxifolin.

Flavonoid-mediated materials are promising substances for the design of new functional materials because of their bioactivity, eco-friendliness, and cost-effectiveness. Dihydroquercetin (DHQ) is the major flavonoid in the wood of Larix dahurica Turcz. Previously some new modifications were created on the basis of DHQ, they were characterized by different morphological, physico-chemical and biopharmaceutical properties. This study was performed to research the influence of the solvent on the formation of the solid phase in DHQ microtubes and crystal form as commercially available active pharmaceutical ingredient (API). The choice of the models for the computational simulation was based on the data of differential scanning calorimetry. All calculations were performed using Materials Science Suite. In silico analysis demonstrated that the molecules of solvent are a key player in the formation of the solid phase of the flavonoid-mediated material. Also the comparative analysis of physical characteristics between DHQ microtubes and crystal form was performed. These data give an opportunity to suggest, that DHQ microtubes may have a grate application as the dressing material and in the drug delivering. The results of this study could be helpful for the design of the new flavonoid-mediated materials by crystal engineering.