Co-Amorphous Systems Based on Dihydroquercetin and l-Lysine: Synthesis and Evaluation

Abstract

Background/Objectives: Dihydroquercetin (DHQ), also known as taxifolin, is a natural flavonoid which has anti-inflammatory and wound-healing biological effects. One of the main limitations for developing formulations with DHQ is its low solubility in water at room temperature. One of the high-potential co-formers for increasing its solubility is l-lysine, which has an aliphatic amino group in the side radical capable of entering into intermolecular interactions with the phenolic hydroxyl groups of DHQ.

Methods: Several modifications were obtained using grinding, drying, and lyophilization methods. Subsequent evaluation was conducted using a combination of physicochemical and biological analytical methods.

Results: Obtained modifications could be described as very easily soluble substances. The absence of the formation of new covalent bonds between the compounds during the formation of such systems was established. The glass transition effect was detected at 64 °C for the obtained films. It is important to note that as a result of studying the cytotoxic properties of the objects, a decrease in cytotoxicity was established during lyophilization of the mechanical mixture of the initial components. For these lyophilizates, the IC50 value was 0.025 mg/mL, 0.068 mg/mL, 0.145 mg/mL, and 0.288 mg/mL for the 3T3, HEK293, Caco-2, and HUVEC cell lines, respectively.

Conclusions: Co-amorphous systems of DHQ and l-lysine in the form of films and lyophilizates were obtained and described. These objects may be interesting from the point of view of increasing the solubility of natural flavonoids, which solves one of the main problems in developing drugs based on them.

Introduction

Dihydroquercetin (DHQ) – 2,3-dihydro-3,5,7-trihydroxy-2-(3,4-dihydroxyphenyl)-4H-1-benzopyran-4-one – also known as taxifolin (Figure 1a), is a natural flavanonol, the main raw material base of which is the wood of Siberian larch (Larix sibirica Ledeb.) and Dahurian larch (Larix dahurica Turcz.) [1]. This compound has demonstrated anti-inflammatory [2,3] and wound-healing [4,5] biological effects. These effects are attributed not only to its pronounced antioxidant activity [6,7] but also to its ability to regulate the expression of genes such as CD68, CD31, and VEGF [8]. Additionally, there is evidence of DHQ activating the AMPK/Nrf2/HO-1 signaling pathway in macrophages, which contributes to the reduction in inflammatory processes [9].

One of the main limitations in developing DHQ-based drugs is its low water solubility at room temperature. According to the European Pharmacopoeia 11.5 [10], its solubility is classified as “very slightly soluble”. This results in limited bioavailability [1], requiring modifications to enhance its suitability for medicinal formulations. Current research primarily focuses on increasing DHQ’s solubility, which in turn improves its bioavailability. Previously explored methods include lyophilization from acetonitrile and methanol solutions [11] and the formation of inclusion complexes with cyclodextrins [12,13]. However, these methods have several limitations, including the limited solubility of the resulting products and the complexity of the technology, which complicates their transfer to industrial production.

Among the approaches aimed at increasing the bioavailability of flavonoids, co-crystallization and co-amorphization [14,15,16] stand out, as they combine ease of implementation with a significant increase in solubility. This makes them an advanced field for further research. One of the most promising co-formers is the amino acid l-lysine (Figure 1b), which contains an aliphatic amino group in its side chain capable of forming intermolecular interactions with the acidic phenolic hydroxyl groups of DHQ. Moreover, amino acids have already been used to produce water-soluble compositions with other flavonoids. For example, the solubility of genistein increased from 5 × 10−5 ± 1 × 10−5 mg/mL for the unmodified flavonoid to 1.919 ± 0.161 mg/mL and 0.938 ± 0.014 mg/mL when combined with lysine and arginine, respectively [17]. Additionally, lysine has demonstrated anti-inflammatory activity by reducing the levels of TNF-α, IL-8, and MIF [18].

Thus, the aim of this study was to develop water-soluble compositions of DHQ and lysine and to characterize their properties. The assessment of the obtained objects was carried out using a range of physicochemical and biological methods of analysis. This allowed us to do a comprehensive characterization and description of the modifications.

Download the full article as PDF here Co-Amorphous Systems Based on Dihydroquercetin and

or continue reading here

Materials

DHQ (95% purity) and state standard reference sample of DHQ (99.99% purity) were purchased from “Ametis” JSC (Blagoveshchensk, Russia). l-lysine monohydrate (98.5–101.0% purity, pharma grade) was provided by NeoFroxx GmbH (Darmstadt, Germany). Needle-modified Dulbecco’s Modified Eagle Medium (DMEM), minimum essential medium (MEM), trypsin solution with ethylenediaminetetraacetate (EDTA), and penicillin/streptomycin (P/S) solution were received from Gibco (Thermo Fisher Scientific Inc., Waltham, MA, USA); fetal bovine serum (FBS) was from ExCell Bio Group (Shanghai, China). Also, 99.9% dimethyl sulfoxide (DMSO) was supplied by Beyotime Inc. (Shanghai, China). Cell counting kit (CCK-8) was provided by Selleck Chemicals LLC (Houston, TX, USA). Biosharp (Hefei, China) provided 0.01 M phosphate-buffered saline (PBS).

Svotin, A.A.; Korochkina, M.D.; Khodyachikh, A.A.; Kolesnikova, D.R.; Taldaev, A.; Bocharov, E.V.; Dzuban, A.V.; Utenyshev, A.N.; Shilov, G.V.; Zeng, Y.; et al. Co-Amorphous Systems Based on Dihydroquercetin and l-Lysine: Synthesis and Evaluation. Pharmaceutics 2025, 17, 1528. https://doi.org/10.3390/pharmaceutics17121528

Read more interesting articles on Freeze Drying here:

• Freeze-drying Technology in Pharmaceutical and Biomedical Product Development
• The Functional Attributes of Co-Processed Excipients in Direct Compression
• What is freeze drying (or lyophilization)?