Binding of curcumin with bovine serum albumin in the presence of ι-carrageenan and implications on the stability and antioxidant activity of curcumin

Construction of quaternary ammonium chitosan-coated protein nanoparticles as novel delivery system for curcumin: Characterization, stability, antioxidant activity and bio-accessibility

This research aimed to develop a novel, effective, and stable delivery system based on zein (ZE), sodium caseinate (SC), and quaternary ammonium chitosan (HACC) for curcumin (CUR). The pH-driven self-assembly combined with electrostatic deposition methods were employed to construct CUR-loaded ZE-SC nanoparticles with HACC coating (ZE-SC@HACC). The optimized nanocomposite was prepared at ZE:SC:HACC:CUR mass ratios of 1:1:2:0.1, and it had encapsulation efficiency of 89.3%, average diameter of 218.2 nm, and ζ-potential of 40.7 mV. The assembly of composites and encapsulation of CUR were facilitated primarily by hydrophobic, hydrogen-bonding, and electrostatic interactions. Physicochemical stability analysis revealed that HACC coating dramatically enhanced ZE-SC nanoparticles' colloidal stability and CUR's resistance to chemical degradation. Additionally, antioxidant activity and simulated digestion results indicated that CUR-ZE-SC@HACC nanoparticles showed higher free radical scavenging capacity and bio-accessibility of CUR than CUR-ZE-SC nanoparticles and free CUR. Therefore, the ZE-SC@HACC nanocomposite is an effective and viable delivery system for CUR.

Interactions of different polyphenols with wheat germ albumin and globulin: Alterations in the conformation and emulsification properties of proteins

In this study, chlorogenic acid (CA), piceatannol (PIC), epigallocatechin-3-gallate (EGCG) and ferulic acid (FA) was selected to explore the influence of polyphenol on the structural properties of wheat germ albumin (WGA) and wheat germ globulin (WGG). The emulsifying properties of the emulsions prepared by WGA-EGCG complex were also evaluated. The results indicated that all polyphenols could significantly enhance the antioxidant capacity of WGA and WGG. In particular, EGCG increased the ratio of random coil in WGA and WGG, resulting in protein unfolding and shifting from an order to disorder structure. In addition, lipid oxidation and protein oxidation of the soybean oil emulsion was significantly slowed down by WGA-EGCG. The stability of the emulsions under various environmental stress and the storage time was significantly improved by WGA-EGCG. These findings can provide a reference for expanding the application of wheat germ protein in food industry.

Non-covalent binding of chlorogenic acid to myofibrillar protein improved its bio-functionality properties and metabolic fate

As natural antioxidants added to meat products, polyphenols can interact with proteins, and the acid-base environment influenced the extent of non-covalent and covalent interactions between them. This study compared the bio-functional characteristics and metabolic outcomes of the myofibrillar protein-chlorogenic acid (MP-CGA) complexes binding in different environments (pH 6.0 and 8.5). The results showed that CGA bound with MP significantly enhanced its antioxidant activity and inhibitory effect on metabolism enzymes. CGA bound deeply into the MP structure hydrophobic cavity at pH 6.0, which reduced its degradation by digestive enzymes, thus increasing its bio-accessibility from 59.5% to 71.6%. The digestion products of the two complexes exhibited significant differences, with the non-covalent MP-CGA complexes formed at pH 6.0 showing significantly higher concentrations of rhetsinine and piplartine, two well-known compounds to modulate diabetes. This study demonstrated that non-covalent binding between protein and polyphenol in the acidic environment held greater promising prospects for improving health.

Targeted Nanoparticles Based on Alendronate Polyethylene Glycol Conjugated Chitosan for the Delivery of siRNA and Curcumin for Bone Metastasized Breast Cancer Applications

Bone metastasized breast cancer reduces the quality of life and median survival. Targeted delivery of small interfering RNA (siRNA) and chemotherapeutic drugs using nanoparticles (NPs) is a promising strategy to overcome current limitations in treating these metastatic breast cancers. This research develops alendronate conjugated polyethylene glycol functionalized chitosan (ALD-PEG-CHI) NP for the delivery of cell death siRNA (CD-siRNA) and curcumin (CUR) and explores its targeting ability and in vitro cell cytotoxicity. Polyethylene glycol functionalized CHI (mPEG-CHI) NPs serve as control. The size of CD-siRNA loaded NPs is below 100 nm while CUR loaded NPs is below 200 nm, with near neutral zeta potential for all NPs. The CUR encapsulation efficiency (EE) is 70% and 88% for targeted and control NPs, respectively, while complete encapsulation of CD-siRNA is achieved in both NP systems. The bone targeting ability of CY5-dsDNA loaded ALD-PEG-CHI NPs using hydroxyapatite discs is fivefold compared to control indicating ALD presentation at the targeting NP surface. Delivery of CD-siRNA loaded NPs and CUR loaded NPs show synergistic and additive growth inhibition effects against MCF-7 cells by mPEG-CHI and ALD-PEG-CHI NPs, respectively. Overall, these in vitro results illustrate the potential of the targeted NPs as an effective therapeutic system toward bone metastasized breast cancer.

Fabrication of nanocomplexes for anthocyanins delivery by ovalbumin and differently dense sulphate half-ester polysaccharides nanocarriers: Enhanced stability, bio-accessibility, and antioxidant properties

This study aimed to fabricate novel nanocomplexes for delivery of anthocyanins (ACN) utilizing ovalbumin (OVA) and sulphated-polysaccharides with varying linear charge density (κ-,ι-, λ-carrageenan and dextran sulfate: κC < ιC < λC < DS). Influence of OVA-sulphated-polysaccharides on ACN stability, antioxidant capacity, and bioaccessibility was investigated. Fabricated nanoparticlecosmeticsed superior encapsulation efficiency (94.11-96.2%) and loaded capacity (9.05-9.54%) for ACN. OVA-DS displayed the smallest particle size and turbidity, while OVA-κC-ACN exhibited the largest ones. ζ-Potential of nanoparticles raised with increasing ester-sulfate level in sulphated-polysaccharides. FT-IR, Raman and OVA conformational alterations revealed existence of intermolecular-interactions between ACN and OVA-polysaccharides. DSC and TGA showed considerable thermo-stability of self-assembled (ACN-loaded) OVA-polysaccharides. Spheroid-nanoparticles size increased after ACN-loading in SEM and CLSM. Composite nanocomplexes enhanced ACN stability and antioxidant properties under accelerated degradation conditions and simulated digestion, particularly, OVA-DS-ACN and OVA-λC-ACN. We provide a choice for reinforcing stability of hydrophilic nutraceuticals and improving its applications.

κ-Carrageenan inhibits the formation of advanced glycation end products in cakes: Inhibition mechanism, cake characteristics, and sensory evaluation

Inhibiting the formation of advanced glycation end products (AGEs) in the heat-processed food can reduce health risks related to diabetic complications. However, additives used for this purpose may also affect the sensory characteristics of food products. In this study, the effects of six hydrocolloids on the formation of AGEs were evaluated in the lysine-glucose model, with κ-carrageenan exhibited the highest inhibitory activity. Mechanistic investigations indicated that κ-carrageenan conjugated with the key intermediates of AGEs, namely glyoxal (GO) and methylglyoxal (MGO). Subsequently, the inhibitory effect of κ-carrageenan on AGEs formation in cakes was verified. The data showed that κ-carrageenan in cakes significantly inhibited the formation of fluorescent and non-fluorescent AGEs. In addition, analysis of cake characteristics and sensory evaluation showed that cakes with 1% (w/w) κ-carrageenan had the highest quality and overall acceptance. Overall, κ-carrageenan is an effective inhibitor of AGEs formation in heat-processed food.

Encapsulating vitamins C and E using food-grade soy protein isolate and pectin particles as carrier: Insights on the vitamin additive antioxidant effects

Functional factors show additive effects in the same nutraceutical food. In this study, a core-shell structure based on soy protein isolate (SPI) and pectin was constructed as a delivery system for vitamins C and E under neutral (pH 7.0) and acidic environment (pH 4.0). The SPI-vitamin-pectin complex formed at pH 4.0 showed larger particle size, higher turbidity, lower fluorescence intensity, and higher vitamin E encapsulation efficiency than those formed at pH 7.0. Also, the addition of vitamin C significantly enhanced the vitamin E encapsulation efficiency in the particles. Furthermore, the antioxidant properties of DPPH, ABTS, and hydroxyl radicals were increased by the addition of vitamin C, maximum values of 77%, 82%, and 65%, suggesting that vitamins C and E have additive antioxidant effects. These findings proposed a simple, structured protein-polysaccharide-based food-grade delivery system, which could serve as the basis for the design of products having multiple functional factors.

Solubilization mechanism of self-assembled walnut protein nanoparticles and curcumin encapsulation

BACKGROUND

Native walnut protein is an alkali-soluble protein that seriously limits the application of walnut protein. The pH-shifting method could improve the solubility of walnut proteins and enable the encapsulation of active ingredients. The present study aimed to prepare water-soluble nanoparticles of curcumin using walnut protein and evaluate the process of walnut protein self-assembly, interaction between walnut protein and curcumin, encapsulation properties, and stability of nanoparticles.

RESULTS

The solubility of native walnut protein was poor, but the solubility of walnut protein nanoparticles (WPNP) formed by walnut protein after pH-shifting significantly improved to 91.5 ± 1.2%. This is because, during the process of pH changing from 7 to 12 and back to 7, walnut protein first unfolded under alkaline conditions and then refolded under pH drive, finally forming an internal hydrophobic and external hydrophilic shell-core structures. The quenching type of walnut protein and curcumin was static quenching, and the quenching constant was 2.0 × 10¹⁴  mol^-1  L^-1  s^-1 , indicating that the interaction between walnut protein and curcumin was non-covalent. Adding curcumin resulted in the formation of nanoparticles with small particle size compared with the no-load. The loading capacity of curcumin-loaded walnut protein nanoparticles (WPNP-C) was 222 mg g^-1 walnut protein isolate. Under the same mass, the curcumin equivalent concentration in aqueous solution of WPNP-C was 17 000 times higher than that of the native curcumin.

CONCLUSION

The solubility of the self-assembled WPNP significantly increased after pH-shifting treatment. The walnut protein carrier could improve the stability of the encapsulated curcumin. Therefore, walnut proteins could be used as water-soluble carriers for hydrophobic drugs. © 2023 Society of Chemical Industry.

Fabrication of glycated yeast cell protein via Maillard reaction for delivery of curcumin: improved environmental stability, antioxidant activity, and bioaccessibility

BACKGROUND

The application of curcumin (CUR) in the food industry is limited by its instability, hydrophobicity and low bioavailability. Yeast cell protein (YCP) is a by-product of spent brewer's yeast, which has the potential to deliver bioactive substances. However, the environmental stresses such as pH, salt and heat treatment has restricted its application in the food industry. Maillard reaction as a non-enzymatic browning reaction can improve protein stability under environmental stress.

RESULTS

The CUR was successfully encapsulated into the hydrophobic core of YCP/glycated YCP (GYCP) and enhanced by hydrogen bonding, resulting in static fluorescence quenching of YCP/GYCP. The average diameter and dispersibility of GYPC-CUR nanocomplex were significantly improved after glucose glycation (121.40 nm versus 139.70 nm). Moreover, the encapsulation capacity of CUR was not influenced by glucose glycation. The oxidative stability and bioaccessibility of CUR in nanocomplexes were increased compared with free CUR, especially complexed with GYCP conjugates.

CONCLUSION

Steric hindrance provided by glucose conjugation improved the enviriomental stability, oxidative activity and bioaccessibility of CUR in nanocomplexes. Thus, glucose-glycated YCP has potential application as a delivery carrier for hydrophobic compounds in functional foods. © 2022 Society of Chemical Industry.

Binding of ankaflavin with bovine serum albumin (BSA) in the presence of carrageenan and protective effects of Monascus yellow pigments against oxidative damage to BSA after forming a complex with carrageenan

Ankaflavin (AK) is a typical yellow pigment extracted from Monascus-fermented rice with several biological effects; however, its solubility is poor. Thus, research studies of the delivery systems of AK, especially those constructed from protein-polysaccharide complexes, have attracted considerable attention. However, the interactions that exist in the system have rarely been investigated. This work focused on the interactions between AK and bovine serum albumin (BSA) as well as the influence of carrageenan (Car) on the binding of AK to BSA. Results revealed that the quenching of BSA by AK involved the static quenching mechanism. The formed BSA-AK complexes were mainly maintained by hydrophobic forces and AK was located within the hydrophobic cavity of BSA. Compared to free AK or AK only complexed with BSA, a higher absorption intensity of AK was observed for the formed BSA-AK-Car complexes, indicating changes in the microenvironment of AK. This was confirmed by the increase in the α-helix content of BSA after the formation of BSA-AK-Car complexes. Hydrogen bond, van der Waals, and electrostatic interactions were verified to be the primary forces preserving the BSA-AK-Car complexes. Moreover, the antioxidant potential of Monascus-fermented products rich in AK (denoted as Mps), namely BSA-Mps and BSA-Mps-Car was evaluated. The antioxidant activity of Mps was negatively impacted by BSA, while the addition of Car could enhance the antioxidant capacity of BSA-Mps-Car complexes. Meanwhile, Mps showed a protective effect against free radical-induced oxidation damage to BSA, and Car could further improve this effect.

Preparation and characterization of curcumin/chitosan conjugate as an efficient photodynamic antibacterial agent

Curcumin (Cur) is a natural pigment with excellent biological activity. The poor stability and insolubility of Cur in water severely limit its application. Therefore, to overcome these dilemmas which are big hindrances in their application, a novel derivative (COCS-Cur) was prepared by the esterification reaction of carboxylated chitosan (COCS) and Cur. The structure and properties of conjugate were determined through a series of characterizations. The derivatives had excellent solubility as well as stability. In addition, antioxidant and photodynamic antibacterial experiments proved that COCS-Cur had the excellent free radical scavenging ability and photodynamic antibacterial activity. The derivatives presented a better antibacterial effect on Staphylococcus aureus (S. aureus) than Escherichia coli (E. coli). Noteworthy, the COCS-Cur derivatives showed no obvious toxicity which makes them a stronger contender and potential antimicrobial agent or functional nutrient for application in the food industry.

New Synthetic Quinoline (Qui) Derivatives as Novel Antioxidants and Potential HSA's Antioxidant Activity Modulators-Spectroscopic Studies

The antioxidant activity of drugs, as well as the influence of drugs on the activity of endogenous antioxidant mechanisms in the human body is of great importance for the course of the disease and the treatment process. Due to the need to search for new therapeutic methods, the study of newly synthesized substances with potential therapeutic activity is necessary. This study aimed to designate some properties and characteristic parameters of new, synthetic quinoline three derivatives-1-methyl-3-allylthio-4-(4'-methylphenylamino)quinolinium bromide (Qui1), 1-methyl-3-allylthio-4-(3'-hydroxyphenylamino)quinolinium bromide (Qui2) as well as 1-methyl-3-allylthio-4-(4'-hydroxyphenylamino)quinolinium bromide (Qui3), including their antioxidant properties, as well as to analyse their activity as the potential modulators of Human Serum Albumin (HSA) antioxidant activity. In order to achieve the goal of the study, spectroscopic methods such as UV-Vis and circular dichroism (CD) spectroscopy have been used and based on the obtained data only slight and probably some surface interaction of quinoline derivatives (Qui1-Qui3) with HSA have been observed. The effect of Qui1-Qui3 on the HSA secondary structure was also insignificant. All analysed quinine derivatives have antioxidant activity against ABTS cation radical, in turn against DPPH radical, only Qui3 has noticeable antioxidant potential. The highest reduction potential by Qui3 as well as (Qui3 + HSA)_complex has been shown. Qui3 mixed with HSA has mostly the synergistic effect against DPPH, ABTS and FRAP, while Qui1 and Qui2 in the presence of HSA mostly have a synergistic and additive effect towards ABTS, respectively. Based on the obtained results it can be concluded that Qui2 and Qui3 can be considered potential modulators of HSA antioxidant activity.

Phosphorylated walnut protein isolate as a nanocarrier for enhanced water solubility and stability of curcumin

BACKGROUND

The low solubility and poor dispersion of alkaline-extracted walnut protein isolate (AWPI) limit its application as a protein-based carrier for the delivery of poorly soluble nutraceuticals, including curcumin. This work investigated the physicochemical characteristics of phosphorylated walnut protein isolate (PWPI) extracted using sodium tripolyphosphate (STP) and evaluated its encapsulation ability.

RESULTS

The results of phosphorus determination, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy confirmed the phosphorylation of the extracted PWPI. Circular dichroism (CD) analysis indicated that PWPI contained higher α-helix and lower β-sheet contents than AWPI. The PWPI prepared at pH 9.0 and 11.0 showed significantly improved solubility, similar surface hydrophobicity, and increased surface charges compared to the AWPI. Fluorescence quenching experiments indicated that the binding affinity of curcumin to PWPI was significantly higher than that of AWPI. When bound to PWPI, the solubility of curcumin in aqueous solution was greatly enhanced, with an 8700-fold increase at a nanocomplex concentration of 10 mg mL^-1 . The complexation of curcumin with PWPI significantly improved the storage stability of curcumin. Additionally, the PWPI-curcumin nanocomplexes showed significantly increased antioxidant capacity.

CONCLUSION

Phosphorylated walnut protein isolate showed greatly improved solubility and strong encapsulation ability, making it a promising nanocarrier for curcumin. © 2022 Society of Chemical Industry.

ι-Carrageenan nanocomposites for enhanced stability and oral bioavailability of curcumin

Background

Carrageenan (CRN), a polygalactan consisting of 15 to 40% ester sulfate, is used in oral controlled-release technology due to its viscosity and large molecular weight. Curcumin (Cur) is a highly potent antioxidant and anti-inflammatory agent against various diseases, such as tumors, liver disease, rheumatism, and Alzheimer’s disease. Although Cur shows excellent effects in the body, it has major problems, such as poor solubility and low bioavailability in water.

Method

Nanocomposites containing Cur were developed by emulsion technique. Cur@CRN was characterized through the viscosity measurement, size analysis, stability test, and loading efficiency. Antioxidant effects was analyzed with DPPH reagent, and anti-inflammatory effects was analyzed by NFkB/IkBr signaling pathway with wester blot. Cellular interaction was confirmed by flow cytometry and confocal images. Especially, permeability test was demonstrated in MDCK and Caco-2 monolayer cells.

Results

Cur@CRN enhanced stability, antioxidant, and anti-inflammatory effects in vitro, compared with other polymer nanocomposites. Sulfate groups (SO₄²⁻) in CRN are transported across cell membranes by anion exchangers of the SLC26 gene families. We confirmed Caco-2 cells expressed SLC26A2 receptors interacted with CRN, expect for Tween 80 and hydroxypropyl cellulose. In contrary, other cells did not interact with CRN due to non-expression of SLC26A2 receptors. Based on this, Cur@CRN showed 44-fold better permeability than free Cur in MDCK cell assay.

Conclusion

Enhanced intestinal permeability of Cur can be applied in various health care facilities with significant antioxidant and anti-inflammatory effects compared with nonformulated Cur. Since the CRN composed of nanocomposites has a high molecular weight, high viscosity, and sulfate groups, it will be a platform that can increase the bioavailability of various insoluble drugs as well as Cur.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40824-021-00236-4.

Co-encapsulation of (-)-epigallocatechin-3-gallate and piceatannol/oxyresveratrol in β-lactoglobulin: effect of ligand-protein binding on the antioxidant activity, stability, solubility and cytotoxicity

The co-encapsulation of multiple bioactive components in a carrier may produce synergistic effects and improve health benefits. In this study, the interactions of β-lactoglobulin (β-LG) with epigallocatechin-3-gallate (EGCG) and/or piceatannol (PIC)/oxyresveratrol (OXY) were investigated by multispectroscopic techniques, isothermal titration calorimetry, and molecular docking. The static quenching mechanism of β-LG by EGCG, PIC and OXY was confirmed by fluorescence spectroscopy and UV-vis absorption difference spectroscopy. The binding sites of these three polyphenols in β-LG were identified by site marking fluorescence experiments and molecular docking. The thermodynamic parameters of the β-LG + EGCG/PIC/OXY binary complex and β-LG + EGCG + PIC/OXY ternary complex were obtained from fluorescence data and used to analyze the main driving force for complex formation. The exothermic binding process was further confirmed by isothermal titration calorimetry. The α-helical content, particle size and morphology of free and ligand-bound β-LG were determined by circular dichroism spectroscopy, dynamic light scattering and transmission electron microscopy, respectively. The effect of EGCG, PIC and OXY on the conformation of β-LG was studied by Fourier transform infrared spectroscopy. In addition, the maximum synergistic antioxidant activity between EGCG and PIC/OXY was obtained by response surface analysis. The effects of β-LG in the binary and ternary systems on the antioxidant activity, stability, solubility and cytotoxicity of the polyphenols were also studied. Finally, the different cytotoxicities of the complexes and nanoparticles of the binary and ternary systems were compared. The results of this study are expected to provide a theoretical basis for the development of β-LG-based carriers co-encapsulating a variety of bioactive components.

Construction and Application of EGCG-Loaded Lysozyme/Pectin Nanoparticles for Enhancing the Resistance of Nematodes to Heat and Oxidation Stresses

Novel nanoparticles (NPs) were constructed with lysozyme (LY) and pectin (Ps) through self-assembly, which were used as a carrier to encapsulate epigallocatechin-3-gallate (EGCG). The binding of EGCG and LY is a static quenching process. Hydrogen bonds might play a major role in the formation of NPs, which has also been verified by a lower binding constant of EGCG with LY/Ps NPs. Meanwhile, EGCG could lead to conformational and microenvironmental changes of LY, resulting in more folding of LY secondary structures. In addition, attaching Ps to LY might inhibit LY aggregation induced by addition of free EGCG. At the LY/Ps mass ratio of 1:1, the constructed LY/Ps NPs had a high EGCG-loading capacity without a significant change in mean particle size, thus, our NPs could be used as an effective nanocarrier for loading EGCG. In vivo, compared with free EGCG, EGCG loaded onto LY/Ps NPs significantly increased Caenorhabditis elegans’ (C. elegans) resistance to heat stress and oxidative injury and prolonged their lifespan. This study provides theoretical basis and reference for constructing nanoactive substance carriers so as to improve the resistance of organisms to heat stress and oxidative damage and to increase their survival rate and extend their lifespan under environment stresses.

"Lighting-up" curcumin nanoparticles triggered by pH for developing improved enzyme-linked immunosorbent assay

In the field of precision medicine, the anticipated features of ideal drug delivery systems (DDS) have high drug loading capacity and effective stimuli-triggered mechanism, which are fitting well with the expected merits of signal labels for enhanced enzyme-linked immunosorbent assay (ELISA). Inspired by this, poly (diallyldimethylammonium chloride)-capped curcumin nanoparticles (PDDA@CUR NPs) with high loading capacity were synthesized as signal labels and further applied to dual-model colorimetric and fluorescence ELISA for the detection of C-reactive protein (CRP). Curcumin (CUR) was elaborately selected as report molecule similar to the roles of drugs in DDS, which dispersed in neutral water exhibits a negligible fluorescence response due to the aggregation of CUR molecules induced quenching effect, stimulated by basic water (BW, pH 12.36), the allochroic effect from colorless to orange occurred and fluorescence restored because of the keto-enol tautomerism in the molecular structure of CUR, just like lighting-up (from signal "OFF" to signal "ON"), yielded a dual-model colorimetric and fluorescent signal readout. PDDA, as a polycationic electrolyte, provided a biological platform that is capable of interacting with CRP label antibodies by virtue of its positive centers. The results show that "lighting-up" CUR NPs-based dual-modal colorimetric and fluorescent ELISA for CRP detection has the merits of easy-to-use, good enough sensitivity and reliability. And more importantly, it brings innovative ideas for the precise identification and quantification of protein biomarkers.

Curcumin encapsulation in nanostructures for cancer therapy: A 10-year overview

Curcumin (CUR) is a phenolic compound present in some herbs, including Curcuma longa Linn. (turmeric rhizome), with a high bioactive capacity and characteristic yellow color. It is mainly used as a spice, although it has been found that CUR has interesting pharmaceutical properties, acting as a natural antioxidant, anti-inflammatory, antimicrobial, and antitumoral agent. Nonetheless, CUR is a hydrophobic compound with low water solubility, poor chemical stability, and fast metabolism, limiting its use as a pharmacological compound. Smart drug delivery systems (DDS) have been used to overcome its low bioavailability and improve its stability. The current work overviews the literature from the past 10 years on the encapsulation of CUR in nanostructured systems, such as micelles, liposomes, niosomes, nanoemulsions, hydrogels, and nanocomplexes, emphasizing its use and ability in cancer therapy. The studies highlighted in this review have shown that these nanoformulations achieved higher solubility, improved tumor cytotoxicity, prolonged CUR release, and reduced side effects, among other interesting advantages.

Insight into the effect of charge regulation on the binding mechanism of curcumin to myofibrillar protein

Myofibrillar proteins (MPs), as a food-grade material, have the potential to improve the solubility and bioavailability of curcumin. However, the interaction mechanism between MPs and curcumin under charge regulation induced by alkaline pH and NaCl was unclear. In this study, the binding between curcumin and MPs at pH 12 was confirmed by the fluorescence quenching under different NaCl concentration (0, 0.3, 0.6 and 0.9 mol/L). Further kinetic experiments showed, MPs possessed a higher affinity to bind curcumin in the presence of NaCl, especially at 0.6 M NaCl. Followed pH shifting from 12 to 7 does not affect UV-Vis absorption spectra of protein-curcumin dispersions. The secondary structure of MPs was not affected by binding with curcumin. Formation of this stable complex can be explained by hydrophobic other than electrostatic interaction. Therefore, the presence of NaCl facilitated exposure of hydrophobic pocket to improve the binding affinity between curcumin and MPs due to the importance of hydrophobic interaction.

Development and characterization of soybean protein isolate and fucoidan nanoparticles for curcumin encapsulation

Curcumin (Cur) is a natural polyphenol with beneficial biological and pharmacological activities; however, it has limited applications owing to its low solubility and light sensitivity. The protein-polysaccharide complex can effectively embed lipid-soluble drugs to increase their stability and dispensability in aqueous solutions. Soybean protein isolate (Spi) and fucoidan (Fuc) were used as a polymer matrix, and core-shell nanoparticles were prepared to encapsulate Cur via electrostatic interaction under acidic and neutral conditions. The structure of the Spi-Fuc nanoparticles was studied via Fourier-transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy. Concurrently, we evaluated the efficacy of the nanoparticles based on stability, drug loading rate, and simulated release. Our results showed that the Spi-Fuc nanoparticles (size, approximately 236.56 nm) had a spherical, core-shell structure and that they could effectively load Cur with an embedding efficiency of >95%; moreover, the system had long-term dispersion stability. Thus, we provide a simple method for Cur delivery, which can also be potentially used for delivering lipid-soluble active ingredients.

Elaboration and characterization of curcumin-loaded soy soluble polysaccharide (SSPS)-based nanocarriers mediated by antimicrobial peptide nisin

Curcumin was recently attracted great interest owing to its multiple bioactivities; however, the use of curcumin was hindered by its poor solubility and stability. In this study, curcumin-nisin-soy soluble polysaccharide nanoparticles (Cur-Nisin-SSPS-NPs, size = 118.76 nm) have been successfully elaborated to improve the application of curcumin. The formation of Cur-Nisin-SSPS-NPs was mediated by amphiphilic and positively charged nisin: SSPS encapsulated nisin, which was mainly driven by electrostatic attraction. And nisin-SSPS complex encapsulated curcumin mainly through hydrophobic interactions between nisin and curcumin. The encapsulation efficiency of curcumin (91.66%) in this novel nanocarriers was significantly higher than that in nanoparticles prepared by a single SSPS (31.82%) or nisin (41.69%), most likely because more hydrophobic regions of nisin were exposed after interacting with SSPS through electrostatic interaction. Consequently, this facile and green nanocarriers improved the solubility/dispersibility and stability of curcumin and nisin, as well as endowed SSPS-based nanoparticles with antioxidant and antimicrobial activities.

Valorisation of stachysetin from cultivated Stachys iva Griseb. as anti-diabetic agent: a multi-spectroscopic and molecular docking approach

Stachys species are considered as important medicinal plants with numerous health benefit effects. In continuation of our research on the Greek Stachys species, the chemical profile of the aerial parts of cultivated S. iva Griseb. has been explored. The NMR profiles of the plant extract/infusion were used to guide the isolation process, leading to the targeted isolation of seventeen known compounds. The rare acylated flavonoid, stachysetin, was isolated for the third time from plant species in the international literature. Identification of the characteristic signals of stachysetin in the 1D ¹H-NMR spectrum of the crude extract was presented. In order to evaluate the potential of the identified chemical space in Stachys to bear possible bioactivity against diabetes, we performed an in silico screening against 17 proteins implicated in diabetes, as also ligand based similarity metrics against established anti-diabetic drugs. The results capitalized the anti-diabetic potency of stachysetin. Its binding profile to the major drug carrier plasma protein serum albumin was also explored along with its photophysical properties suggesting that stachysetin could be recognized and delivered in plasma through serum albumin and also could be tracked through near-infrared imaging. Communicated by Ramaswamy H. Sarma.

Structures, fabrication mechanisms, and emulsifying properties of self-assembled and spray-dried ternary complexes based on lactoferrin, oat β-glucan and curcumin: A comparison study

Protein-polyphenol-polysaccharide non-covalent ternary complexes possess many unique structural and functional properties. However, rare work is available to fabricate the neutral polysaccharide-based ternary complexes. Herein, the ternary complexes composed of lactoferrin (LF), oat β-glucan (OG), and curcumin (Cur) with three binding sequences were successfully developed through self-assembly technique and spray drying technique, respectively. Spray drying could enhance the extent of the intermolecular associations among LF, OG, and Cur, leading to the formation of ternary complexes with smaller particle sizes and lower turbidities. Cur can be loaded in LF-OG complexes to form an amorphous complex through the intermolecular interactions (mainly hydrophobic interactions and hydrogen bonding). The ternary complexes can be used as potential emulsifiers to stabilize oil-in-water Pickering emulsions. The emulsifying capacity (to enhance physical stability) of the complexes was in the order as follows: the spray-dried ternary complexes > the spray-dried LF-OG complexes > the self-assembled ternary complexes > the self-assembled LF-OG complexes. The structural and functional properties (e.g., emulsifying property) of OG-based ternary complexes can be controlled by adjusting the binding sequences. These results will broaden our current understanding of protein-polyphenol-polysaccharide ternary complexes and provide more applications of OG in food, cosmetics, and pharmaceutical industries.

Comparative study on the interaction of oxyresveratrol and piceatannol with trypsin and lysozyme: binding ability, activity and stability

Natural polyphenols showing a variety of beneficial effects will interact with multiple proteases after administration. The interactions of oxyresveratrol and piceatannol with trypsin and lysozyme were investigated using fluorescence spectroscopy, UV-vis absorption spectroscopy, circular dichroism spectroscopy, differential scanning calorimetry and molecular docking. Fluorescence quenching results and UV-vis absorption difference spectra revealed that the quenching process was a static mode initiated by ground-state complex formation. The different binding ability of oxyresveratrol and piceatannol with trypsin and lysozyme was discussed based on their different molecular structures. Moreover, the major driving force for the binding process was elucidated as hydrogen bonding and van der Waals forces by the negative enthalpy and entropy changes. Synchronous fluorescence, three-dimensional fluorescence and circular dichroism spectral analysis suggested that the binding of oxyresveratrol and piceatannol to trypsin and lysozyme induced some microenvironmental and conformational changes of the two enzymes. The thermal stability of the enzymes in the presence of polyphenols was studied based on the change in melting temperature by differential scanning calorimetry. The above experimental results were validated by the protein-ligand docking studies which showed the location of the two ligands in the enzymes and the surrounding amino acid residues. Furthermore, enzyme activity assays indicated that the enzymatic activity of trypsin and lysozyme was inhibited by oxyresveratrol and piceatannol. The effect of trypsin and lysozyme on the antioxidant activity and stability of oxyresveratrol and piceatannol was also investigated. In conclusion, the comparative study on the interaction of oxyresveratrol and piceatannol with trypsin and lysozyme showed that the positions of hydroxyl groups of the polyphenols had an important influence on their interaction with enzymes and their antioxidant activity and stability as well as the enzyme activities. The obtained results are expected to provide a theoretical basis for the application of polyphenols in functional foods and pharmaceuticals.

Biophysical interactions between silver nanoparticle-albumin interface and curcumin

Active targeted drug delivery methods facilitate effective uptake of functionalized nanoparticles through receptor-mediated transcytosis. In recent years, albumin-nanoparticle interaction has been critically examined so that this functionalized nanoparticle can be efficiently loaded with drugs. The present investigation aims at understanding the adsorption of Bovine Serum Albumin (BSA) on Silver Nanoparticle (SNP) surface, preparation of soft conjugates (SC) and hard conjugates (HC) of BSA-functionalized SNP (SNP-BSA), and their interaction with curcumin (CUR). HC contains tightly bound BSA whereas SC involves tightly and loosely bound BSA. Increase in the hydrodynamic radii of conjugates was observed upon SNP incubation with increased concentration of BSA. Three different SNP-BSA conjugate ratios were selected to study their interaction with CUR. Fluorescence spectroscopy showed a strong association between CUR and SNP:BSA conjugates. However, binding varied with a change in the conjugate ratio. Circular Dichroism (CD)/Fourier Transform Infrared (FTIR) spectroscopy revealed the alterations in the secondary structure of BSA upon CUR binding to the conjugates. Zeta potential data indicated stable conjugate formation. CUR in SNP:BSA conjugate was found to have a higher half-life as compared to the control. We believe that this is the first biophysical characterization report of conjugates that can be effectively extrapolated for targeted drug delivery.

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Soft Conjugates (SC) and Hard conjugates (HC) of Bovine Serum Albumin (BSA) and Silver nanoparticles (SNP) were prepared and interaction with anticancer drug CUR was explored.

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Binding number and adsorption capacity of drug was identified.

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Conformational and microenvironment changes in adsorbed BSA upon SNP and CUR interaction were investigated.

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Best possible conjugates were identified for efficient loading of CUR drug.

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Drug designed can be further studied for its interaction with glycoprotein receptor present on the diseased (cancerous) cell.

Molecular insight on the binding of monascin to bovine serum albumin (BSA) and its effect on antioxidant characteristics of monascin

Monascin (MS) is a yellow lipid-soluble azaphilonoid pigment identified from Monascus-fermented products with promising biological activities. This work studied interactions between MS and bovine serum albumin (BSA) as well as their influences on the antioxidant activity of MS. Experimental results demonstrated that the fluorescence emission of BSA was quenched by MS via static quenching mechanism and the formed BSA-MS complex was mainly maintained by hydrophobic and hydrogen bond interactions. Meanwhile, the probable binding pocket of MS located near site I of BSA and the corresponding conformational and structural alterations of BSA were determined. Furthermore, the molecular modeling approach was performed to understand the visual representation of binding mode between BSA and MS. It was noticeable that the BSA-MS complex exhibited reduced DPPH radical-scavenging ability, which might be attributed to the restraining effect of BSA on the relevant reaction pathways involved in antioxidation by MS.

Effect of Oil Content and Emulsifier Type on the Properties and Antioxidant Activity of Sea Buckthorn Oil-in-Water Emulsions

Sea buckthorn oil-in-water emulsions were prepared through high pressure homogenization, and the effects of droplet size, oil content, and emulsifier type on emulsion properties and the overall antioxidant activity of the emulsions were evaluated. Emulsions with different droplet size were obtained by varying homogenization pressure, and higher oil content resulted in bigger droplet size of the emulsions. Among three tested emulsifiers, sodium caseinate and sugar ester were able to form emulsions with much smaller particle size than soy protein isolate. The emulsions with bigger droplets tended to cream in an accelerated centrifugation test. The antioxidant property of the emulsions was expressed as their DPPH radical scavenging activity. The emulsions processed at lower pressure or contained higher oil content had higher DPPH radical scavenging activity. The soy protein isolate-stabilized emulsion presented higher antioxidant activity than sodium caseinate- and sugar ester-stabilized ones. Upon storage, the antioxidant activity of the emulsions was decreased due to the changes in emulsion stability and the degradation of antioxidants. The knowledge obtained in this study would be useful in developing healthy food containing sea buckthorn oil.

A new dendrimer series: synthesis, free radical scavenging and protein binding studies

Tri-o-tolyl benzene-1,3,5-tricarboxylate (TOBT (T0)), tri-4-hydroxyphenyl benzene-1,3,5-tricarboxylate (THBT (T1)), and tri-3,5-dihydroxyphenyl benzene-1,3,5-tricarboxylate (TDBT (T2)), a series of 1^st tier dendrimers with a common 1,3,5-benzenetricarbonyl trichloride/trimesoyl chloride (TMC) core, are reported. T0 does not have any replaceable H⁺ on its terminal phenyl group, acting as a branch. T1 has one phenolic –OH at the para position and T2 has two phenolic –OH groups at the 3 and 5 positions of each terminal phenyl group. During synthesis, these –OH groups at the terminal phenyl groups were protected through tert-butyldimethylsilyl chloride (TBDMSCl) assisted with t-BuOK in DCM, THF, indazole, 4-dimethylaminopyridine (DMAP), and tertiary-n-butyl ammonium fluoride (TBAF). MTBDMSP (mono-tertiary butyl dimethylsilane phloroglucinol), DTBDMSP (di-tertiary butyl dimethylsilane phloroglucinol), and TTBDMSP (tri-tertiary butyl dimethylsilane phloroglucinol) were obtained with >90% yield, and TTBDMSP phenolic derivatives (PDs) were developed to synthesize T0, T1, and T2 dendrimers by deprotecting with TBAF. T0 showed superhydrophobic properties as it did not dissolve in methanol, contrary to T1 and T2, but dissolved in acetone. Their structures were determined using ¹H and ¹³C NMR spectroscopies, and mass spectrometry. Their scavenging activities were studied using UV-Vis spectrophotometry compared with ascorbic acid and protein binding was studied with bovine serum albumin (BSA) and lysozyme (lyso). T0 exhibited exceptional optical activity contrary to T1 and T2, which acted as antioxidants to scavenge free radicals.

Superhydrophobic dendrimers with excellent antioxidant properties, and the ability to bind proteins and enzymes in their functional void spaces.

GSH-responsive curcumin/doxorubicin encapsulated Bactrian camel serum albumin nanocomposites with synergistic effect against lung cancer cells

The aim of this study was to prepare camel serum albumin (CSA) nanoparticles using a self-assembly strategy to co-immobilize curcumin (CCM) and doxorubicin (Dox) which was in favor of combined chemotherapy and biomedical applications of bactrian ( Camelus bactrianus) CSA. The constructed CSA nanoparticles (CSA-NPs) with the size around 200 nm displayed a high degree of polydispersity and further encapsulation of CCM and Dox caused no apparent morphological changes to the nanocomposite (CCM/Dox CSA-NPs). The synergistic cytotoxic effect of CCM and Dox on cancer cell A549 was observed with the calculated combination index less than 1.0. Moreover, the release kinetic profile of encapsulated drugs showed a concentration dependence of glutathione (GSH) originating from the GSH used in nanoparticle formation to break the intramolecular disulfide bonds. In vitro cytotoxicity evaluations also revealed that CCM/Dox CSA-NPs showed higher cytotoxicity than that of single drug loaded CSA-NPs, which was also validated by high content screen assay. Taken together, the CCM/Dox CSA-NPs with redox-responsive attributes provided an integrated protein-based combinational drug-delivery matrix to exert synergistic effects.

Explication of bovine serum albumin binding with naphthyl hydroxamic acids using a multispectroscopic and molecular docking approach along with its antioxidant activity

In the present investigation, the protein-binding properties of naphthyl-based hydroxamic acids (HAs), N-1-naphthyllaurohydroxamic acid (1) and N-1-naphthyl-p-methylbenzohydroxamic acid (2) were studied using bovine serum albumin (BSA) and UV-visible spectroscopy, fluorescence spectroscopy, diffuse reflectance spectroscopy-Fourier transform infrared (DRS-FTIR), circular dichroism (CD), and cyclic voltammetry along with computational approaches, i.e. molecular docking. Alteration in the antioxidant activities of compound 1 and compound 2 during interaction with BSA was also studied. From the fluorescence studies, thermodynamic parameters such as Gibb's free energy (ΔG), entropy change (ΔS) and enthalpy change (ΔH) were calculated at five different temperatures (viz., 298, 303, 308, 313 or 318 K) for the HAs-BSA interaction. The results suggested that the binding process was enthalpy driven with dominating hydrogen bonds and van der Waals' interactions for both compounds. Warfarin (WF) and ibuprofen (IB) were used for competitive site-specific marker binding interaction and revealed that compound 1 and compound 2 were located in subdomain IIA (Sudlow's site I) on the BSA molecule. Conclusions based on above-applied techniques signify that various non-covalent forces were involved during the HAs-BSA interaction. Therefore the resulted HAs-BSA interaction manifested its effect in transportation, distribution and metabolism for the drug in the blood circulation system, therefore establishing HAs as a drug-like molecule.