Sustained-Release Microspheres of Cyclodextrin–Resveratrol Complex Using Fenugreek Galactomannan Hydrogels: A Green Approach to Phytonutrient Delivery
Abstract
Food matrices are becoming increasingly complex with the impregnation of phytonutrients with health-beneficial pharmacological effects. Herein, we report the preparation, characterization, and functional application of soluble and stable microspheres of trans-resveratrol (t-RES) developed through a water-based green process involving cyclodextrin (CD) and fenugreek galactomannan (FG). Spectroscopic and thermodynamic calculations identified γ-CD as the best CD to form a stable cyclodextrin–resveratrol inclusion complex (CD-R, 49-fold enhanced solubility); however, it exhibited a burst release profile. The sustained release of resveratrol was achieved by further encapsulating the inclusion complex within the fenugreek galactomannan hydrogel scaffold by a gel-phase dispersion process, resulting in an amorphous powder (FG-CD-R) as evident from powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) studies. Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) studies confirmed the formation of the inclusion complex with no chemical alterations. When dissolved in water, FG-CD-R swelled and released stable cuboid structures with an average particle size of 500 ± 53 nm with a zeta potential of −52 ± 5.3 mV. FG-CD-R demonstrated a sustained-release profile upon in vitro release studies. Accelerated study demonstrated its stability for a shelf-life of two years. Further it was shown to be suitable for the preparation of transparent gummies with improved sensory attributes compared to unformulated t-RES. In summary, FG-CD-R is simple to prepare and easily scalable, providing a sustained-release t-RES with a natural, food-grade, and clean label status (non-genetically modified, allergen-free, vegan, and free from residual solvents) for nutritional applications.
Introduction
Resveratrol (3,4′,5-trihydroxy-trans-stilbene), a naturally occurring polyphenolic phytoalexin compound found in several plants such as grapes, berries, peanut sprouts, and herbs, is a typical example of hydrophobic and water-insoluble phytonutrients. It offers a wide spectrum of health benefits such as anticancer effect, (1) but with poor bioavailability. Resveratrol exists in two isomeric forms, namely cis and trans, in which trans-resveratrol (t-RES) is dominant and more bioactive. (1) Recently, there has been a growing interest for t-RES, in both the food and pharmaceutical industries due to its antioxidant, anti-inflammatory, antiglycemic, cardioprotective, neuroprotective, and anticancer properties. (2,3) However, various animal and human pharmacokinetic studies have indicated that its poor bioavailability (<1%) is a major limitation for its therapeutic and functional benefits. (4)
Low water solubility (<20 μg/mL), instability in the gastrointestinal tract, rapid biotransformation to glucuronides and sulfates, and a relatively short elimination half-life (<2 h) have been identified as the major factors limiting the bioavailability of t-RES. (5) A number of encapsulation technologies and vehicles have been reported to address these issues, including liposomes, (6) modified protein nanoparticles, emulsions, oleogels, micelles, and hydrogels. (7−11) Despite enhancements in solubility and bioavailability achieved with many of these formulations, their applications in food and nutraceuticals are limited due to the extensive use of synthetic, nonfood grade surfactants. Some of the widely used synthetic emulsifiers include Cremophor EL, polysorbates, polyglycerol polyricinoleate, Labrasol, Transcutol P, etc., (5,12,13) and polymers include cross-linked polystyrene polymers, cross-linked poly(methyl methacrylate)s, polyethylene glycol-caprolactone block copolymers, polyglycerol copolymers, lactic acid–glycolic acid copolymers, etc. (14−16) Still, there is scope for using natural food-grade polymers to develop “green” approaches in phytonutrient delivery.
Cyclodextrin (CD)-based inclusion complexes have been widely reported in both pharmaceuticals and nutraceuticals to improve solubility, stability, and bioavailability of hydrophobic compounds. (17) Cyclodextrins are cyclic oligosaccharides composed of d-glucopyranose units linked by α-(1,4) glycosidic bonds to produce CDs with 6, 7, and 8 units, commonly referred to as α-, β-, and γ-cyclodextrins respectively. (18) They are Generally Recognized as Safe (GRAS) by the Food and Drug Administration (FDA) and are approved as food ingredients in the USA, Europe, Japan, and other countries. (19) Cyclodextrins, especially β-CDs such as hydroxypropyl-β-CD and randomly methylated-β-CD, have been reported to form soluble inclusion complexes with t-RES. However, their bioavailability showed little improvement when ingested. (20) The reason is attributed to its rapid drug release and fast systemic clearance. Furthermore, sustained-release formulations of t-RES were reported to overcome the issue of burst release. Carbonyldiimidazole-cross-linked CD nanosponges showed better permeation in in vitro studies. (21) Similarly, a codelivery formulation of t-RES and curcumin using pyromellitic dianhydride cross-linked CD nanosponges improved permeation and anticancer activity against breast cancer cells. (22) However, such modifications find limited applications for nutrients due to the extensive usage of chemicals.
We hypothesized that impregnation of the inclusion complex within a hydrogel scaffold might modulate its release properties. Thus, in the present study, we attempted the uniform impregnation of cyclodextin–resveratrol inclusion complex (CD-R) within a soft hydrogel scaffold produced from fenugreek (Trigonella foenum graecum)-soluble dietary fiber (galactomannan). Here, we report our investigation into the optimized complexation of t-RES with various CDs (α-, β-, and γ-CDs) under varying conditions of pH and temperature and their solubility. The optimized complex was then subjected to structural, thermal, and morphological studies, with special emphasis on in vitro release, mechanism of interaction, and thermodynamics. Fluorescence studies were conducted to correlate the nature and thermodynamic parameters of the CD-R complexation. The optimized CD-R complex was further modified with fenugreek galactomannan hydrogel (FG-CD-R) to engineer sustained-release properties and to be applied as a functional food ingredient.
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Materials and Methods
Various grades of cyclodextrin were provided by Wacker Chemie AG (Mumbai, India). trans-Resveratrol (t-RES, 99%) was obtained as a gift sample from Akay Natural Ingredients Private Limited (Kochi, India). Pepsin and pancreatin were procured from Sigma-Aldrich (St. Louis, USA) and SRL Private Limited (Mumbai, India), respectively. All other chemicals, reagents, and solvents were of analytical grade (unless otherwise specified) and were purchased from Merck, Mumbai, India.
Following excipients are mentioned in the study besides other: hydroxypropyl-β-CD, α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrins
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CPHI Milan 2024 – with a focus on excipients
