Formulation of More Efficacious Curcumin Delivery Systems Using Colloid Science: Enhanced Solubility, Stability, and Bioavailability

Curcumin: Modern Applications for a Versatile Additive

The recent development of several methods for extracting curcumin from the root of the plant Curcuma longa has led to intensified research on the properties of curcumin and its fields of application. Following the studies and the accreditation of curcumin as a natural compound with antifungal, antiviral, and antibacterial properties, new fields of application have been developed in two main directions—food and medical, respectively. This review paper aims to synthesize the fields of application of curcumin as an additive for the prevention of spoilage, safety, and quality of food. Simultaneously, it aims to present curcumin as an additive in products for the prevention of bacterial infections and health care. In both cases, the types of curcumin formulations in the form of (nano)emulsions, (nano)particles, or (nano)composites are presented, depending on the field and conditions of exploitation or their properties to be used. The diversity of composite materials that can be designed, depending on the purpose of use, leaves open the field of research on the conditioning of curcumin. Various biomaterials active from the antibacterial and antibiofilm point of view can be intuited in which curcumin acts as an additive that potentiates the activities of other compounds or has a synergistic activity with them.

Protective Effects of Curcumin on the Outcome of Cryopreservation in Human Sperm

Cryopreservation causes decreased sperm fertility potential due to reactive oxygen species (ROS) production and physical-chemical damage, resulting in reduced sperm viability and motility. The addition of antioxidants to freezing media could protect sperm from cryo-damage, counteracting the harmful effects of ROS. The aim of this study was to assess the effects of curcumin supplementation in freezing medium on preventing cryo-damage in human semen. Semen samples collected from fertile men were cryopreserved in freezing medium supplemented with different concentrations of curcumin (2.5, 5, 10, and 20 μM). After freezing-thawing, sperm parameters, DNA fragmentation, intracellular ROS, and glutathione peroxidase 4 (GPX4) gene expression were evaluated. Supplementation with 20 μM curcumin in freezing medium caused increases in progressive and nonprogressive motility and significant reductions in intracellular ROS and DNA fragmentation in frozen-thawed sperm cells. Following cryopreservation, GPX4 mRNA expression was significantly upregulated in thawed semen supplemented with 20 μM curcumin compared to the control. The results showed that curcumin supplementation in freezing medium was protective against human sperm parameters and sperm DNA, counteracting oxidative damage induced by the freeze-thaw process.

Hydrogel Films Based on Chitosan and Oxidized Carboxymethylcellulose Optimized for the Controlled Release of Curcumin with Applications in Treating Dermatological Conditions

Cross-linked chitosan (CS) films with aldehyde groups obtained by oxidation of carboxymethyl cellulose (CMC) with NaIO4 were prepared using different molar ratios between the CHO groups from oxidized carboxymethyl cellulose (CMCOx) and NH2 groups from CS (from 0.25:1 to 2:1). Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy demonstrated the aldehyde groups' presence in the CMCOx. The maximum oxidation degree was 22.9%. In the hydrogel, the amino groups' conversion index value increased when the -CHO/-NH2 molar ratio, cross-linking temperature, and time increased, while the swelling degree values decreased. The hydrogel films were characterized by scanning electron microscopy (SEM) and FTIR analysis. The curcumin encapsulation efficiency decreases from 56.74% to 16.88% when the cross-linking degree increases. The immobilized curcumin release efficiency (REf%) and skin membrane permeability were evaluated in vitro in two different pH solutions using a Franz diffusion cell, and it was found to decrease when the molar ratio -CH=O/NH2 increases. The curcumin REf% in the receptor compartment was higher at pH = 7.4 (18%- for the sample with a molar ratio of 0.25:1) than at pH = 5.5 (16.5%). The curcumin absorption in the skin membrane at pH = 5.5 (47%) was more intense than at pH = 7.4 (8.6%). The curcumin-loaded films' antioxidant activity was improved due to the CS presence.

Improvement of the bioavailability of curcumin by a supersaturatable self nanoemulsifying drug delivery system with incorporation of a hydrophilic polymer: in vitro and in vivo characterisation

OBJECTIVES

The current study was focused on preparing curcumin (CUR) supersaturated self-nano-emulsion (PI-CUR-SNEDDS) using hydrophilic polymer and to study the influence of polymer precipitation inhibitor on the physicochemical and biopharmaceutical properties of the PI-CUR-SNEDDS.

METHODS

PI-CUR-SNEDDS were prepared using hydrophilic polymer in order to maintain the supersaturation of CUR in nano-emulsion solution, artificial gastrointestinal fluid (AGF), and the precipitates formed, and characterised by in vitro dispersion tests, in vitro intestinal absorption and in vivo pharmacokinetic and compared with CUR-SNEDDS.

KEY FINDINGS

PI-CUR-SNEDDS prepared with 2% hydroxypropyl methylcellulose 55-60 (HPMC55-60) as precipitation inhibitor (PI) significantly improved the viscosity, physical stability and CUR's equilibrium solubility of nanoemulsion. HPMC55-60 and CUR interact in AGF through intermolecular interactions, form hydrogen bonds, and produce amorphous precipitates. Compared with CUR-SNEDDS, the proportion of CUR in the hydrophilic phase increased by about 3-fold, and apparent permeability coefficient (Papp) in duodenum, jejunum, ileum, and colon increased by 2.30, 3.65, 1.54 and 2.08-fold, respectively, and the area under the plasma concentration-time curve0-12h of PI-CUR-SNEDDS also increased by 3.50-fold.

CONCLUSIONS

Our results suggested that HPMC55-60 maintained the CUR supersaturation state by forming hydrogen bonds with CUR, increasing the solution's viscosity and drug solubilisation, thus improving the absorption and bioavailability of CUR.

In Vitro Gastrointestinal Stability of Lipophilic Polyphenols is Dependent on their Oil-Water Partitioning in Emulsions: Studies on Curcumin, Resveratrol, and Quercetin

Many lipophilic polyphenols have low bioavailability because of their poor solubility and chemical stability within the human gut. The encapsulation of these polyphenols within digestible lipid droplets can improve their solubility and stability. However, there is currently a poor understanding of how the molecular and physicochemical properties of specific polyphenols impact these characteristics. In this study, the factors influencing the solubility and stability of different polyphenols (curcumin, resveratrol, and quercetin) under simulated gastrointestinal conditions were examined when they were delivered in the form of soybean oil-in-water nanoemulsions containing quillaja saponin-coated droplets (d₃₂ ≈ 0.15 μm; ζ = -63 mV; pH 5). The polyphenols were loaded into the lipid droplets using a pH-driven method, which is based on the pH-dependent electrical charge, oil-water partitioning, and water-solubility of these molecules. The encapsulation efficiency of all three polyphenols was relatively high (75-87%). However, their chemical stability under gastrointestinal conditions (i.e., the % remaining after exposure to gastrointestinal conditions) differed considerably: quercetin (44%), curcumin (92%), and resveratrol (100%). This effect was mainly attributed to the lower logD value of quercetin (2.17) than those of resveratrol (3.39) and curcumin (4.12). As a result, a high fraction (>50%) of quercetin was located within the aqueous gastrointestinal fluids, where it would be more prone to chemical degradation or precipitation. The fraction of the polyphenols solubilized in the gastrointestinal fluids (bioaccessibility) followed a different trend: curcumin (57%) < quercetin (73%) < resveratrol (76%). This effect was attributed to the chemical instability and/or binding of curcumin with other molecules in the simulated intestinal conditions. These results provide useful information for designing nanoemulsion-based delivery systems to improve the efficacy of lipophilic polyphenols.

Nanoemulsions for Enhancement of Curcumin Bioavailability and Their Safety Evaluation: Effect of Emulsifier Type

This work aimed at evaluating the effects of different emulsifiers on curcumin-loaded nanoemulsions’ behavior during digestion, its safety and absorption, to develop nanoemulsions that provide safety and improved curcumin functionality. Nanoemulsions (NEs) were produced using two bio-based (lecithin (LEC) and rhamnolipids (RHAM)) and one synthetic (Tween^®80 (TWE)) emulsifier at similar concentrations. Different NEs were subjected to in vitro digestion. The cytotoxicity and permeability tests were performed in Caco-2 cells. NE_TWE were stable during all phases of in vitro digestion, whereas NE_LEC and NE_RHAM were found to be unstable from the gastric phase. NE_TWE showed 100% of free fatty acids released, followed by NE_RHAM and NE_LEC. Curcumin’s bioaccessibility and stability increased in the following order: NE_LEC > NE_RHAM > NE_TWE. NE_LEC and NE_TWE did not show cytotoxic effects in any of the concentrations tested, while NE_RHAM presented high cytotoxicity in all concentrations tested. The apparent permeability coefficients were determined for NE_LEC and NE_TWE; however, the results were not statistically different. These results showed that the emulsifier used has a high impact on nanoemulsions’ behavior under the digestion process and on their cytotoxicity. This work contributed to the state-of-the-art’s progress on the development of safer curcumin delivery systems with improved functionality, particularly regarding the proper selection of ingredients to produce said systems.

The Formation of Chitosan-Coated Rhamnolipid Liposomes Containing Curcumin: Stability and In Vitro Digestion

There is growing interest in developing biomaterial-coated liposome delivery systems to improve the stability and bioavailability of curcumin, which is a hydrophobic nutraceutical claimed to have several health benefits. The curcumin-loaded rhamnolipid liposomes (Cur-RL-Lips) were fabricated from rhamnolipid and phospholipids, and then chitosan (CS) covered the surface of Cur-RL-Lips by electrostatic interaction to form CS-coated Cur-RL-Lips. The influence of CS concentration on the physical stability and digestion of the liposomes was investigated. The CS-coated Cur-RL-Lips with RL:CS = 1:1 have a relatively small size (412.9 nm) and positive charge (19.7 mV). The CS-coated Cur-RL-Lips remained stable from pH 2 to 5 at room temperature and can effectively slow the degradation of curcumin at 80 °C; however, they were highly unstable to salt addition. In addition, compared with Cur-RL-Lips, the bioavailability of curcumin in CS-coated Cur-RL-Lips was relatively high due to its high transformation in gastrointestinal tract. These results may facilitate the design of a more efficacious liposomal delivery system that enhances the stability and bioavailability of curcumin in nutraceutical-loaded functional foods and beverages.

Water-in-Oil-in-Water Nanoemulsions Containing Temulawak (Curcuma xanthorriza Roxb) and Red Dragon Fruit (Hylocereus polyrhizus) Extracts

Hydrophobic curcumin in temulawak extract and hydrophilic betacyanin in red dragon fruit extract are high-value bioactive compounds with extensive applications in functional food. In this study, these extracts were encapsulated in water-in-oil-in-water (w/o/w) nanoemulsions as a delivery system using a two-step high-energy emulsification method. PGPR and Span 20 were used as lipophilic emulsifiers for the primary w/o emulsion. The most stable w/o/w formulation with the least oil phase separation of 5% v/v consisted of w/o emulsion (15% w/w) and Tween 80 (1.5% w/w) as hydrophilic emulsifier. The formulation was characterized by a 189-nm mean droplet diameter, 0.16 polydispersity index, and –32 mV zeta potential. The freeze–thaw stability may be attributed to the combination of low w/o emulsion content and high Tween 80 concentration in the outer water phase of the w/o/w nanoemulsions used in this study. The IC₅₀ values of the nanoemulsion and the red dragon fruit extract were similar. It means that the higher concentration of curcumin in the nanoemulsions and the lower IC₅₀ value of temulawak extract ensured sufficient antioxidant activities of the w/o/w nanoemulsions.