Application of the Box–Behnken Design in the Development of Amorphous PVP K30–Phosphatidylcholine Dispersions for the Co-Delivery of Curcumin and Hesperetin Prepared by Hot-Melt Extrusion

Abstract

Background: Curcumin and hesperetin are plant polyphenols known for their poor solubility. To address this limitation, we prepared amorphous PVP K30–phosphatidylcholine dispersions via hot-melt extrusion.

Methods: This study aimed to evaluate the effects of the amounts of active ingredients and phosphatidylcholine, as well as the process temperature, on the performance of the dispersions. A Box–Behnken design was employed to assess these factors. Solid-state characterization and biopharmaceutical studies were then conducted. X-ray powder diffraction (XRPD) was used to confirm the amorphous nature of the dispersions, while differential scanning calorimetry (DSC) provided insight into the miscibility of the systems. Fourier-transform infrared spectroscopy (FTIR) was employed to assess the intermolecular interactions. The apparent solubility and dissolution profiles of the systems were studied in phosphate buffer at pH 6.8. In vitro permeability across the gastrointestinal tract and blood–brain barrier was evaluated using the parallel artificial membrane permeability assay.

Results: The quantities of polyphenols and phospholipids were identified as significant factors influencing the biopharmaceutical performance of the systems. Solid-state analysis confirmed the formation of amorphous dispersions and the development of interactions among components. Notably, a significant improvement in solubility was observed, with formulations exhibiting distinct release patterns for the active compounds. Furthermore, the in vitro permeability through the gastrointestinal tract and blood–brain barrier was enhanced.

Conclusions: The findings suggest that amorphous PVP K30–phosphatidylcholine dispersions have the potential to improve the biopharmaceutical properties of curcumin and hesperetin.

Introduction

Curcumin is the main active ingredient found in the popular spice turmeric (Curcuma longa L.). This polyphenol is claimed to have a range of beneficial health-promoting properties that can be utilized in the treatment and prevention of chronic diseases. Curcumin is reported to exhibit antioxidant [1,2], anti-inflammatory [3,4], anticancer [5,6], antidiabetic [7,8], and neuroprotective [9,10,11] activities. Another promising polyphenol is hesperetin, a flavonoid found in citrus fruits. The compound has shown antioxidant [12], anti-inflammatory [13,14], anti-tumor [15,16], antidiabetic [17,18], and neuroprotective [19,20] effects. It is worth noting that co-administration of curcumin and hesperetin may provide synergistic neuroprotective effects by involving complementary mechanisms of action, thereby enhancing the effectiveness of treatment [21]. Research by Lee et al. showed that both curcumin and hesperetin exhibit significant antioxidant capabilities, which help reduce oxidative stress—a key factor in neurodegeneration—thereby protecting neuronal cells from damage. Moreover, the combination of these plant compounds modulated apoptotic pathways, decreasing the expression of pro-apoptotic proteins (like Bax) and increasing anti-apoptotic proteins (like Bcl-2), suggesting a protective effect against neuronal cell death. One study demonstrated that the combination of curcumin and hesperetin improved cognitive function in aged rats induced with D-galactose. The combined treatment showed notable effects, promoting neuron growth and reducing markers of cellular senescence [21]. However, both compounds suffer from low solubility, which limits their bioavailability and prevents them from demonstrating their full therapeutic potential. Many research groups have attempted to improve the bioavailability of these compounds. For curcumin fabrication of self-assembled cyclodextrin succinate/chitosan nanoparticles [22], the manufacturing of solid self-emulsifying systems [23] and production of pH-driven zein/tea saponin composite nanoparticles [24] have been reported. For hesperetin, techniques such as the creation of self-assembling rebaudioside A nanomicelles [25], nanoemulsions [26], and zein/pectin nanoparticles [27] have been developed.

One well-established technique for improving solubility is the conversion of the drug’s form from crystalline to amorphous. The amorphous form lacks long-range order, which results in increased solubility and dissolution rates compared to the crystalline form [28,29,30,31]. To prevent crystallization during dissolution and ensure physical stability, the addition of excipients such as polymers, is often necessary [32]. Another effective method for improving oral bioavailability is the use of phospholipids to prepare complexes with active substances [33,34,35]. Because of their ability to self-organize, micelles form during dissolution, which solubilizes the active compound [36]. Combining both mechanisms to enhance bioavailability may be a promising approach to formulation development.

This work aimed to develop amorphous polymer–phospholipid dispersions of curcumin and hesperetin to improve their biopharmaceutical potential. The goal of the research was achieved through several steps. Hot-melt extrusion technology was employed to produce the amorphous dispersions. Then, the Box–Behnken experimental design was selected to determine whether the amount of active substances, the quantity of phosphatidylcholine, and the temperature of the process significantly affected the solubility of the active compounds. The processed systems were subsequently subjected to solid-state characterization, followed by an evaluation of their biopharmaceutical properties. The novelty of this paper lies in the development of amorphous PVP K30–phosphatidylcholine dispersions aimed at increasing the solubility of poorly soluble plant compounds. Systems combining different solubility enhancement mechanisms—polymer and phospholipid dispersions—may represent an innovative solution for improving biopharmaceutical properties.

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Materials

Hesperetin (purity > 95%) was sourced from Sigma-Aldrich (St. Louis, MO, USA), while curcumin (purity > 95%) was obtained from Xi’an Tian Guangyuan Biotech Co., Ltd. (Xi’an, China). The excipients were provided by the following manufacturers: PVP K30 and phosphatidylcholine (from dried egg yolk, purity 100%; CAS number: 8002-43-5; product number: 61771) from Sigma-Aldrich (St. Louis, MO, USA) and xylitol from Santini (Poznań, Poland). Other reagents included sodium hydroxide (Avantor Performance Materials Poland S.A., Gliwice, Poland), acetic acid (98–100%; POCH, Gliwice, Poland), sodium dimethyl sulfoxide (DMSO; Pan-Reac Appli-Chem ITW Reagents, Darmstadt, Germany), acetic acid (J. T. Baker, Center Valley, PA, USA), and HPLC-grade methanol (J. T. Baker, Center Valley, PA, USA). High-quality laboratory-grade water was produced using a Direct-Q 3 UV purification system (Millipore, Molsheim, France; model Exil SA 67120). The Prisma HT, GIT/BBB lipid solution, and acceptor sink buffer were supplied by Pion Inc. (Forest Row, East Sussex, UK).

Wdowiak, K.; Tajber, L.; Miklaszewski, A.; Cielecka-Piontek, J. Application of the Box–Behnken Design in the Development of Amorphous PVP K30–Phosphatidylcholine Dispersions for the Co-Delivery of Curcumin and Hesperetin Prepared by Hot-Melt Extrusion. Pharmaceutics 2025, 17, 26. https://doi.org/10.3390/pharmaceutics17010026

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