Antibacterial hop extracts encapsulated in nanochitosan matrices

Synthesis of β-acids loaded chitosan-sodium tripolyphosphate nanoparticle towards controlled release, antibacterial and anticancer activity

The development of nanoparticles loaded with natural active ingredients is one of the hot trends in the pharmaceutical industry. Herein, chitosan was selected as the base material, and sodium tripolyphosphate was chosen as the cross-linking agent. Chitosan nanoparticles loaded with β-acids from hops were prepared by the ionic cross-linking method. The results of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that chitosan nanoparticles successfully encapsulated β-acids. The loading capacity of chitosan nanoparticles with β-acids was 2.00 %-18.26 %, and the encapsulation efficiency was 0.58 %-55.94 %. Scanning electron microscopy (SEM), transmission electron microscope (TEM), particle size, and zeta potential results displayed that the nanoparticles revealed a sphere-like distribution with a particle size range of 241-261 nm, and the potential exhibited positive potential (+14.47-+16.27 mV). The chitosan nanoparticles could slowly release β-acids from different simulated release media. Notably, the β-acids-loaded nanoparticles significantly inhibited Staphylococcus aureus ATCC25923 (S. aureus) and Escherichia coli ATCC25922 (E. coli). Besides, β-acids-loaded chitosan nanoparticles were cytotoxic to colorectal cancer cells (HT-29 and HCT-116). Therefore, applying chitosan nanoparticles can further expand the application of β-acids in biomedical fields.

Green Synthesis of Zein-Based Nanoparticles Encapsulating Lupulone: Antibacterial and Antiphotoaging Agents

Prolonged skin exposure to UV radiation may result in sunburn, with possible inflammatory and oxidative stress to the skin, skin photoaging, photocarcinogenesis, even DNA damage, and apoptosis if sunscreen protection is not used. Due to the advantages that they offer, high encapsulation capability, increased stability of encapsulated bioactive agents, and release control, nanoparticulate materials have been used in sunscreens despite the hazard that they present: their capacity to penetrate the skin causing toxic side effects (especially the chemical sunscreens). The present study reports the preparation of nanoparticulate composites containing only GRAS substances and using an eco-friendly, inexpensive procedure. The ingredients used have properties that are beneficial to the skin. Zein (Z), a prolamin-rich protein from corn, is biodegradable and biocompatible, is a moisture attractor, and shows effective absorption by cells. Lupulone (L), extracted from hops, is an antibacterial and antioxidant agent that has a stimulating effect on the collagen production in the body due to its content of phytohormones. Gum arabic (GA) is a natural glycoprotein used in beverages and cosmetics as an emulsifier/stabilizer. Composite matrices containing Z/GA/L were prepared using a simple method (antisolvent), which replaces the flammable solvent ethanol with aqueous propylene glycol. The nanocomposites were characterized by FTIR, composition, encapsulation efficiency, and loading capacity for L, size, zeta potential, and morphology (SEM). Their biological activity was investigated as well. The zein-based nanoparticles showed antioxidant and antimicrobial effects (even some synergistic, unexpected behavior) and modulatory activity on the matrix metalloproteinase MMP-1. Due to their properties, the nanoparticles discussed herein show potential for use in formulations for the skin, especially for mature skin, replacing chemical substances with potential side effects used typically in topical delivery systems.

Sophorolipid-based microemulsion delivery system: Multifaceted enhancement of physicochemical properties of xanthohumol

Xanthohumol (XN) has numerous compelling physiological activities, but the poor solubility and stability severely limit its utilization. Therefore, a microemulsion (ME) delivery system based on biosurfactant sophorolipids (SLs) was established and its improvement on physicochemical properties of XN was investigated. The results showed that the systems increased the solubility of XN by about 4000 times, and its half-life during storage was extended to over 150 days. Partial replacement of Tween 80 with SL did not greatly affect their ability to form O/W subregions (in the high aqueous phase), but further improved the solubilization efficiency, storage stability, and antioxidant properties of XN. In vitro models revealed the release profile of XN from the systems followed non-Fickian diffusion, and the ME structure markedly strengthened its digestive stability and bioaccessibility. These results indicated that SL-based ME systems had great potential as a green solubilization and delivery method for XN and other hydrophobic drugs.

Preparation and characterization of a solid dispersion of Hexahydrocolupulone and its application in the preservation of fresh apple juice

Hops extracts and their derivatives have many important biological activities, among them, excellent antibacterial and antioxidant properties make them a promising food preservative. However, poor water solubility limits their application in the food industry. This work aimed to improve the solubility of Hexahydrocolupulone (HHCL) by preparing solid dispersion (SD) and investigating the application of the obtained products (HHCL-SD) in actual food systems. HHCL-SD was prepared by solvent evaporation with PVPK30 as a carrier. The solubility of HHCL was dramatically increased to 24.72 mg/mL（25 ℃)by preparing HHCL-SD, much higher than that of raw HHCL (0.002 mg/mL). The structure of HHCL-SD and the interaction between HHCL and PVPK30 were analyzed. HHCL-SD was confirmed to have excellent antibacterial and antioxidant activities. Furthermore, the addition of HHCL-SD proved to be beneficial for the sensory, nutritional quality, and microbiological safety of fresh apple juice, hence prolonging its shelf-life.

Impact of tannic acid on nisin encapsulation in chitosan particles

This study investigates the effect of addition of tannic acid on nisin encapsulated in chitosan matrices. Composite materials were prepared using a mild, environmentally friendly procedure, ionotropic gelation of chitosan by sodium tripolyphosphate in the presence of nisin (N) at different concentrations. In two parallel sets of preparations, tannic acid (TA) was added at 10:1 and 5:1 N:TA, respectively. The obtained particles were characterized by FTIR, SEM, size, zeta potential, encapsulation efficiency, loading capacity, and ratio of residual free amino groups. The kinetics of nisin release from the particles was studied to assess the role of TA as a potential modulator thereof. Its addition resulted in enhanced release, higher at lower N:TA ratio. An additional benefit was that TA, a strong antioxidant, imparted antioxidant activity to the composites. Antimicrobial turbidimetric tests were performed against one gram-positive bacterium (Staphylococcus aureus) and two gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), all relevant for the food, pharmaceutical, and cosmetic industries. All the composites showed synergistic effects against all the bacteria tested. The positive coaction was stronger against the gram-negative species. This is remarkable since nisin by itself has not known activity against them.

Freeze-Drying Microencapsulation of Hop Extract: Effect of Carrier Composition on Physical, Techno-Functional, and Stability Properties

In this study, freeze-drying microencapsulation was proposed as a technology for the production of powdered hop extracts with high stability intended as additives/ingredients in innovative formulated food products. The effects of different carriers (maltodextrin, Arabic gum, and their mixture in 1:1 w/w ratio) on the physical and techno-functional properties, bitter acids content, yield and polyphenols encapsulation efficiency of the powders were assessed. Additionally, the powders' stability was evaluated for 35 days at different temperatures and compared with that of non-encapsulated extract. Coating materials influenced the moisture content, water activity, colour, flowability, microstructure, and water sorption behaviour of the microencapsulates, but not their solubility. Among the different carriers, maltodextrin showed the lowest polyphenol load yield and bitter acid content after processing but the highest encapsulation efficiency and protection of hop extracts' antioxidant compounds during storage. Irrespective of the encapsulating agent, microencapsulation did not hinder the loss of bitter acids during storage. The results of this study demonstrate the feasibility of freeze-drying encapsulation in the development of functional ingredients, offering new perspectives for hop applications in the food and non-food sectors.

The Antimicrobial Activity of Curcumin and Xanthohumol on Bacterial Biofilms Developed over Dental Implant Surfaces

In search for natural products with antimicrobial properties for use in the prevention and treatment of peri-implantitis, the purpose of this investigation was to evaluate the antimicrobial activity of curcumin and xanthohumol, using an in vitro multi-species dynamic biofilm model including Streptococcus oralis, Actinomyces naeslundii, Veillonella parvula, Fusobacterium nucleatum, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans. The antimicrobial activities of curcumin (5 mM) and xanthohumol (100 μM) extracts, and the respective controls, were evaluated with 72-h biofilms formed over dental implants by their submersion for 60 seconds. The evaluation was assessed by quantitative polymerase chain reaction (qPCR), confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). For the data analysis, comparisons were tested applying ANOVA tests with post-hoc Bonferroni corrections to evaluate the antimicrobial activity of both extracts. With qPCR, statistically significant reductions in bacterial counts were observed for curcumin and xanthohumol, when compared to the negative control. The results with CLSM and SEM were consistent with those reported with qPCR. It was concluded that both curcumin and xanthohumol have demonstrated antimicrobial activity against the six bacterial species included in the dynamic in vitro biofilm model used.

The Taste-Masking Mechanism of Chitosan at the Molecular Level on Bitter Drugs of Alkaloids and Flavonoid Glycosides from Traditional Chinese Medicine

Taste masking of traditional Chinese medicines (TCMs) containing multiple bitter components remains an important challenge. In this study, berberine (BER) in alkaloids and phillyrin (PHI) in flavonoid glycosides, which are common bitter components in traditional Chinese medicines, were selected as model drugs. Chitosan (CS) was used to mask their unfriendly taste. Firstly, from the molecular level, we explained the taste-masking mechanism of CS on those two bitter components in detail. Based on those taste-masking mechanisms, the bitter taste of a mixture of BER and PHI was easily masked by CS in this work. The physicochemical characterization results showed the taste-masking compounds formed by CS with BER (named as BER/CS) and PHI (named as PHI/CS) were uneven in appearance. The drug binding efficiency of BER/CS and PHI/CS was 50.15 ± 2.63% and 67.10 ± 2.52%, respectively. The results of DSC, XRD, FTIR and molecular simulation further indicated that CS mainly masks the bitter taste by disturbing the binding site of bitter drugs and bitter receptors in the oral cavity via forming hydrogen bonds between its hydroxyl or amine groups and the nucleophilic groups of BER and PHI. The taste-masking evaluation results by the electronic tongue test confirmed the excellent taste-masking effects on alkaloids, flavonoid glycosides or a mixture of the two kinds of bitter components. The in vitro release as well as in vivo pharmacokinetic results suggested that the taste-masked compounds in this work could achieve rapid drug release in the gastric acid environment and did not influence the in vivo pharmacokinetic results of the drug. The taste-masking method in this work may have potential for the taste masking of traditional Chinese medicine compounds containing multiple bitter components.

Evaluating hop extract concentrations found in commercial beer to inhibit Streptococcus mutans biofilm formation

AIMS

The purpose of this study was to compare the effect of hop extracts with diverse β-acid concentrations on Streptococcus mutans biofilm formation.

METHODS AND RESULTS

Ten different hop extracts, with α-acid concentrations similar to those found in commercial beer products and β-acid concentrations ranging from 2.6 to 8.1%, were added to distilled water to make standardized concentrations. S. mutans isolates were treated with hop extract dilutions varying from 1:2 to 1:256. The minimum inhibitory, minimum bactericidal, and minimum biofilm inhibitory concentrations were determined and the optical density was evaluated. Live/dead staining confirmed the bactericidal effects. Biofilm formation of several strains of S. mutans was significantly inhibited by hop extract dilutions of 1:2, 1:4, 1:8, 1:16, and 1:32. Strong negative correlations were observed between α- and β-acid concentrations of the hop extracts and S. mutans total growth and biofilm formation.

CONCLUSIONS

The use of hop extracts prepared similarly to commercial beer decreased S. mutans biofilm formation.

SIGNIFICANCE AND IMPACT OF THE STUDY

The inclusion of hops in the commercial beer products may provide beneficial health effects. Further studies are warranted to determine an effect in vivo on the development of dental caries.

Antibacterial effects of biologically active ingredients in hop provide promising options to fight infections by pathogens including multi-drug resistant bacteria

Antibiotic resistance constitutes a global threat to the health care systems. The number of infections due to multidrug-resistant (MDR) bacteria increases progressively resulting in an estimated annual number of 750,000 fatal cases worldwide. Additionally, the lack of novel antibiotic compounds worsens the dilemma. Hence, there is an urgent need for alternative ways to fight antibiotic resistance. One option may be natural compounds with antibacterial properties such as hop and its biologically active ingredients which are used in traditional medicine since ancient times. This prompted us to perform an actual literature survey regarding the antibacterial properties of biologically active ingredients in hop including humulone, lupulone and xanthohumol. The 20 included studies revealed that lupulone and xanthohumol do in fact inhibit the growth of Gram-positive bacteria in vitro. In combination with distinct antibiotic compounds the hop ingredients can even exert synergistic effects resulting in enhanced antibiotic activities against defined Gram-positive and Gram-negative bacteria. In conclusion, biologically active ingredients in hop including lupulone and xanthohumol may be potential antibiotic compounds which either alone or in combination with other antibacterial substances open novel avenues in the combat of infections caused by pathogenic including MDR bacteria.

Conductive polypyrrole-coated electrospun chitosan nanoparticles/poly(D,L-lactide) fibrous mat: influence of drug delivery and Schwann cells proliferation

For nerve tissue engineering (NTE), scaffolds with the ability to release drugs under control and support the rapid proliferation of cells are very important for the repair of nerve defects. This study aimed to fabricate a conductive drug-loaded fiber mat by electrospinning and assess its potential as a scaffold for Schwann cells proliferation. The conductive polypyrrole (PPy) was coated on an electrospun poly (D, L-lactide) (PLA) fibrous mat, which was simultaneously embedded with protein-loaded chitosan nanoparticles and ibuprofen as a model small molecule drug. The fibrous mat shows suitable conductivity, mechanical properties, and hydrophilicity for NTE. For drug release and degradation studies, the fibrous mat can achieve sustained release of bovine serum albumin (BSA) and ibuprofen, and the PPy coating can increase the surface wettability and conductivity while slowing down the degradation of the fibrous mat. The application of electrical stimulation (ES) to the fibrous mat can accelerate the release of ibuprofen, but there was no significant effect on the release rate of the protein. The fibrous mat showed no cytotoxicityin vitro, and Schwann cells (SCs) can adhere, grow, and proliferate well on mats. At the 120th hour of culturein vitro, the relative growth rate of SCs on the conductive drug-loaded fibrous mat reached 198.22 ± 2.34%, which was an increase of 37.93% compared to the SCs on the drug-loaded fibrous mat with ES. The density and elongation of SCs on the conductive drug-loaded fibrous mat were greater than those on the PLA fibrous mat, indicating that the conductive polypyrrole-coated electrospun chitosan nanoparticles/PLA fibrous mat has good potential for application in nerve regeneration.

Novel Clotrimazole and Vitis vinifera loaded chitosan nanoparticles: Antifungal and wound healing efficiencies

Chitosan integrated nanoparticles of clotrimazole and Egyptian Vitis vinifera juice extract was evaluated in order to maximize the antifungal activity and reduce the gross side effects. In the present study Egyptian Thompson Seedless Vitis vinifera and Clotrimazole (Cz) loaded chitosan nanoparticles (NCs/VJ/Cz) showed a promising antifungal effect with average inhibition zone diameters of 74 and 72 mm against Candida albicans and Aspergillus niger respectively. NCs/VJ /Cz was stable with significant drug entrapment efficiency reached 94.7%; PDI 0.24; zeta potential value + 31 and average size 35.4 nm diameter. Ex vivo and in vivo evaluation of skin retention, permeation and wound repair potentialities of NCs/VJ /Cz ointment was examined by experimental rats with wounded skin fungal infection. Data proved the ability of NCs/VJ /Cz to gradually release the drugs in a sustained manner with complete wound healing effect and tissue repair after 7 days administration. As a conclusion NCs/VJ /Cz ointment can be used as a novel anti-dermatophytic agent with high wound healing capacity.

Chitin and chitosan on the nanoscale

In a matter of decades, nanomaterials from biomass, exemplified by nanocellulose, have rapidly transitioned from once being a subject of curiosity to an area of fervent research and development, now reaching the stages of commercialization and industrial relevance. Nanoscale chitin and chitosan, on the other hand, have only recently begun to raise interest. Attractive features such as excellent biocompatibility, antibacterial activity, immunogenicity, as well as the tuneable handles of their acetylamide (chitin) or primary amino (chitosan) functionalities indeed display promise in areas such as biomedical devices, catalysis, therapeutics, and more. Herein, we review recent progress in the fabrication and development of these bio-nanomaterials, describe in detail their properties, and discuss the initial successes in their applications. Comparisons are made to the dominant nanocelluose to highlight some of the inherent advantages that nanochitin and nanochitosan may possess in similar application.

Hop bitter acids: resources, biosynthesis, and applications

Diversified members of hop bitter acids (α- and β-acids) have been found in hop (Humulus lupulus). Mixtures of hop bitter acids have been traditionally applied in brewing and food industries as bitterness flavors or food additives. Recent studies have discovered novel applications of hop bitter acids and their derivatives in medicinal and pharmaceutical fields. The increasing demands of purified hop bitter acid promoted biosynthesis efforts for the heterologous biosynthesis of objective hop bitter acids by engineered microbial factories. In this study, the updated information of hop bitter acids and their representative application in brewing, food, and medicine fields are reviewed. We also speculate future trends on the development of robust microbial cell factories and biotechnologies for the biosynthesis of hop bitter acids. KEY POINTS: • Structures and applications of hop bitter acids are summarized in this study. • Biosynthesis of hop bitter acids remains challenging. • We discuss potential strategies in the microbial production of hop bitter acids.

Nanosystems for the Encapsulation of Natural Products: The Case of Chitosan Biopolymer as a Matrix

Chitosan is a cationic natural polysaccharide, which has emerged as an increasingly interesting biomaterialover the past few years. It constitutes a novel perspective in drug delivery systems and nanocarriers' formulations due to its beneficial properties, including biocompatibility, biodegradability and low toxicity. The potentiality of chemical or enzymatic modifications of the biopolymer, as well as its complementary use with other polymers, further attract the scientific community, offering improved and combined properties in the final materials. As a result, chitosan has been extensively used as a matrix for the encapsulation of several valuable compounds. In this review article, the advantageous character of chitosan as a matrix for nanosystemsis presented, focusing on the encapsulation of natural products. A five-year literature review is attempted covering the use of chitosan and modified chitosan as matrices and coatings for the encapsulation of natural extracts, essential oils or pure naturally occurring bioactive compounds are discussed.

Replacement of nitrite with lupulon-xanthohumol loaded nanoliposome in cooked beef-sausage: experimental and model based study

Replacement of nitrite with hop components in cooked beef-sausage (CBS) was studied. For this purpose, lupulon-xanthohumol loaded nanoliposome (L-X-NL) was produced using sonication at optimized condition (time = 10.8 min, power = 72.7 W, lecithin concentration = 140 mg/mL). The release of lupulon and xanthohumol to liquid meat extract followed the Rigter-Peppus model. Samples of CBS (60% meat) supplemented by different ratios of nitrite/L-X-NL were produced. Microbial analysis and lipid oxidation measurement were carried out to evaluate the safety of CBS samples. The formulation consisted 30 ppm of nitrite and 150 ppm of L-X-NL remained microbiologically safe during 30-d storage at 4 °C. It was observed that L-X-NL could postpone the oxidation. Addition of L-X-NL has not impaired the sensory properties of final product, while the presence of nitrite for inducing the demanding color of CBS was important. Considering the results, partial removal of nitrite in formulation of CBS (up to 50%) and replacing with L-X-NL as a new promising preservative is recommended.

Enhanced antimycotic activity of nanoconjugates from fungal chitosan and Saussurea costus extract against resistant pathogenic Candida strains

Targeting the control of pathogenic Candida spp., especially the fungicides resistant strains from C. albicans and C. glabrata, nanoconjugates from the biopolymer (chitosan) and costus root extract (Saussurea costus) was synthesized and characterized. Chitosan was extracted from the grown mycelia of Aspergillus niger and characterized with high deacetylation degree of 91.2% and moderate molecular weight of 106.8 kDa. Synthesis of nanoconjugates from fungal chitosan/costus extract (NCt/CE) was conducted using ionic gelation technique; the resulted NCt/CE particles were characterized with mean diameter of 48 nm, positive zeta potentiality (+3.28 mV) and high stability. The infra-red spectra of synthesized nanoconjugates indicated their strong biochemical cross-linkage. The antimycotic activities, of the synthesized NCt, CE and their nanocomposite, were evaluated against standard and antibiotic-resistant strains from C. albicans and C. glabrata and revealed that the entire agents had notable antimycotic potentiality against all examined strains; the NCt/CE nanoconjugates had significantly stronger antimicrobial action. The scanning microscope imaging, of exposed resistant strains to NCt/CE, indicated their vigorous structural and morphological alterations and confirmed the antimycotic activity of the nanocomposite. NCt/CE nanoconjugates' synthesis could be exceedingly recommended as a natural, biodegradable and effectual antimycotic agent to control resistant pathogenic yeast strains.

Chitosan based self-assembled nanocapsules as antibacterial agent

Creating an appropriate antibacterial disinfection system without forming any harmful compounds is still a major challenge and calls for new technologies for efficient disinfection and microbial control. Towards this aim, we report on the elaboration of biodegradable and biocompatible polymeric nanocapsules, also called hollow nanoparticles, for potential applications in antibiotic therapy. These nanomaterials are based on the self-assembly of charged polysaccharides, namely chitosan and alginate, onto gold nanoparticles as a sacrificial matrix (60 nm). Electrostatic interactions between the protonated amine groups of chitosan (+35 mV) and the carboxylate groups of alginate (- 20 mV) are the driving attraction force enabling the elaboration of well-ordered multilayer films onto the spherical substrate. The removal of the colloidal gold, via cyanide-assisted hydrolysis, is evidenced by time-dependent variation of the gold spectroscopic signature (30 min is required). TEM shows the obtention of nanocapsules. An inhibitory effect of these particles has been demonstrated during the growth of two representative bacteria in a liquid medium: Staphylococcus aureus (Gram-positive) (from 4.6% to 16.3% for gold nanomaterials ⁺ and from 18.6% to 34.9% for (chi⁺/alg^-)_n-chi⁺ nanocapsules) and Escherichia coli (Gram-negative) (from 5.4% to 20% for gold nanomaterials and from 23.7% to 40% for (chi⁺/alg^-)_n-chi⁺ nanocapsules). Acridine orange staining demonstrated the bactericidal effect of chitosan-based capsules. These findings demonstrate that (chitosan/alginate)_n capsules can be exploited as new antibacterial material. Thus, we present a complementary approach to classical nanoparticles prepared by complexation between alginate and chitosan or other materials.