Synthesis of amide derivatives containing capsaicin and their antioxidant and antibacterial activities

The development of nanocarriers for natural products

Natural bioactive compounds from plants exhibit substantial pharmacological potency and therapeutic value. However, the development of most plant bioactive compounds is hindered by low solubility and instability. Conventional pharmaceutical forms, such as tablets and capsules, only partially overcome these limitations, restricting their efficacy. With the recent development of nanotechnology, nanocarriers can enhance the bioavailability, stability, and precise intracellular transport of plant bioactive compounds. Researchers are increasingly integrating nanocarrier-based drug delivery systems (NDDS) into the development of natural plant compounds with significant success. Moreover, natural products benefit from nanotechnological enhancement and contribute to the innovation and optimization of nanocarriers via self-assembly, grafting modifications, and biomimetic designs. This review aims to elucidate the collaborative and reciprocal advancement achieved by integrating nanocarriers with botanical products, such as bioactive compounds, polysaccharides, proteins, and extracellular vesicles. This review underscores the salient challenges in nanomedicine, encompassing long-term safety evaluations of nanomedicine formulations, precise targeting mechanisms, biodistribution complexities, and hurdles in clinical translation. Further, this study provides new perspectives to leverage nanotechnology in promoting the development and optimization of natural plant products for nanomedical applications and guiding the progression of NDDS toward enhanced efficiency, precision, and safety. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Optimization of Ultrasound-Assisted Extraction and Characterization of the Phenolic Compounds in Rose Distillation Side Streams Using Spectrophotometric Assays and High-Throughput Analytical Techniques

Lately, the essential oils industry has been one of the most expanding markets globally. However, the byproducts generated after the distillation of aromatic plants and their transformation to novel high-added value products consist of a major up-to-date challenge. Thus, the scope of the current study is the optimization of ultrasound-assisted extraction (UAE) for the recovery of phenolic compounds from rose (Rosa damascena) post-distillation side streams using Box-Behnken design. In particular, the highest total phenolic content (TPC) was achieved at 71% v/v ethanol-water solution, at 25 min, 40 mL/g dry sample and 53% ultrasound power, while ethanol content and extraction time were the most crucial factors (p-value ≤ 0.05) for UAE. Both solid (RSB) and liquid (LSB) rose side streams exhibited significant antiradical and antioxidant activities. The interpretation of attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra confirmed the presence of compounds with properties such as phenolic compounds, phenolic amide derivatives, and alcohols in the extracts. Moreover, the flavonoids naringenin, quercetin, and kaempferol were the major phenolic compounds, identified in the extracts by liquid chromatography-tandem mass spectrometry analysis (LC-MS/MS), followed by gallic, protocatechuic, p-hydroxybenzoic, and rosmarinic acids. Furthermore, the LC-MS/MS results pinpointed the effect of factors other than the extraction conditions (harvesting parameters, climatic conditions, plant growth stage, etc.) on the phenolic fingerprint of RSB extracts. Therefore, RSB extracts emerge as a promising alternative antioxidant agent in food products.

Preparation of capsaicin-loaded ultrafine fiber film and its application in the treatment of oral ulcers in rats

A drug-loaded diaphragm is an easy-to-use and effective drug delivery system that is often used to treat mouth ulcers. In this study, an ultrafine fiber film loaded with capsaicin was successfully prepared using the electrospinning technology. poly-L-lactic acid and gelatin were selected as the matrix materials to form the composite fiber, and trifluoroethanol was used as a co-solvent for poly-L-lactic acid, gelatin and capsaicin to prepare the spinning solution, which was simple to fabricate. The prepared fiber films were characterized based on their microscopic morphology and tested to derive their mechanical properties. Thereafter, the capsaicin release behavior of the film was investigated. In vitro experiments revealed certain anti-inflammatory and antibacterial abilities while animal experiments revealed that the capsaicin-loaded ultrafine fiber film could promote the healing of oral ulcers in rats. Healing of the tongue tissue in rats administered 10% capsaicin-loaded fiber film was found to be better than that in rats administered the commercial dexamethasone patch. Overall, this development strategy may prove to be promising for the development of oral ulcer patch formulations.

Effect of Capsaicin Addition on Antioxidant Capacity, Immune Performance and Upper Respiratory Microbiota in Nursing Calves

Capsaicin (CAP) has various biological activities; it has antibacterial, anti-inflammatory and antioxidant properties, and stimulates intestinal development. The aim of this study was to investigate the effect of CAP on the health of nursing calves under group housing conditions. Twenty-four newborn Holstein calves were randomly assigned to three treatment groups of eight calves each. The milk replacer was supplemented with 0, 0.15 or 0.3 mL/d of CAP in each of the three treatment groups. Following a one-month clinical trial of individual-pen housing, an extended one-month trial of group housing was conducted. At the end of the trial, serum samples, rectal fecal samples and upper respiratory swab samples were collected to determine the effect of CAP addition on serum parameters, fecal fermentation parameters and upper respiratory microbiota of calves under group housing conditions. The results showed that the addition of high doses of CAP decreased calf respiratory scores (p < 0.05), increased serum glutathione peroxidase, superoxide dismutase, immunoglobulin A, immunoglobulin G, immunoglobulin M and interleukin-10 concentration (p < 0.05), and decreased malondialdehyde, amyloid A and haptoglobin concentration (p < 0.05). Moreover, high doses of CAP increased the rectal fecal concentration of total short-chain fatty acids, acetate and butyric acid (p < 0.05). In addition, CAP regulated the upper respiratory tract microbiota, with high doses of CAP reducing Mycoplasma abundance (p < 0.05), two doses of CAP reducing Corynebacterium abundance (p < 0.05) and a tendency to reduce Staphylococcus abundance (p = 0.06). Thus, CAP can improve calf antioxidant capacity, immune capacity and reduce inflammatory factors, stress proteins as well as improve gut fermentation and upper respiratory microbiota under group housing conditions, which is beneficial for healthy calf growth.

The Effect of Capsaicin on Growth Performance, Antioxidant Capacity, Immunity and Gut Micro-Organisms of Calves

Capsaicin is the active ingredient of the red pepper plant of the genus Capsicum. The aim of this study was to investigate the effects of different doses of capsaicin on growth performance, antioxidant capacity, immunity, fecal fermentation parameters and gut microbial composition in nursing calves. Twenty-four newborn Holstein calves were randomly assigned to three treatment groups, which each consisted of eight calves. The milk replacer was supplemented with 0, 0.15 or 0.3 mL/d of capsaicin in each of the three treatment groups. During the 4-week experiment, intake was recorded daily, body weight and body size parameters were measured at the beginning and end of the trial and serum samples and rectal fecal samples were collected at the end of the trial to determine serum parameters, fecal fermentation parameters and fecal microbiome compartments. The results showed that both doses of capsaicin had no negative effect on the growth performance or the fecal fermentation parameters of calves, and the higher dose (0.3 mL/d) of capsaicin significantly improved the antioxidant capacity and immunity of calves. The calves in the high-dose capsaicin-treated group had lower fecal scores than those recorded in the control group. High doses of capsaicin increased glutathione antioxidant enzyme, superoxide dismutase, immunoglobulin A, immunoglobulin G, immunoglobulin M and interleukin-10 levels and decreased malondialdehyde and bound bead protein levels. In addition, capsaicin regulated the gut microbiota, reducing the abundance of diarrhea-associated bacteria, such as Eggerthella, Streptococcus, Enterococcus and Enterobacteriaceae, in the gut of calves in the treated group. Therefore, high doses of capsaicin can improve the antioxidant and immune capacity of calves without affecting growth performance, as well as improve the gut microbiological environment, which enables the healthy growth of calves.

Probing the mechanism of interaction between capsaicin and myofibrillar proteins through multispectral, molecular docking, and molecular dynamics simulation methods

The interaction between myofibrillar proteins (MPs) and capsaicin (CAP) was investigated using multispectral, molecular docking, and molecular dynamics simulation methods. The resulting complex increased the hydrophobicity of the tryptophan and tyrosine microenvironment as revealed by fluorescence spectral analysis. The fluorescence burst mechanism study indicated that the fluorescence burst of CAP on the MPs was a static one (Kq = 1.386 × 10¹² m^-1s^-1) and that CAP could bind with MPs well (Ka = 3.31 × 10⁴ L/mol, n = 1.09). The analysis of circular dichroism demonstrated that the interaction between CAP and MPs caused a decrease in the α-helical structure of MPs. The complexes formed exhibited lower particle size and higher absolute ζ potential. Furthermore, hydrogen bonding, van der Waals forces, and hydrophobic interactions were found to be the primary factors facilitating the interaction between CAP and MPs, as suggested by molecular docking models and molecular dynamics simulations.

Capsaicin-loaded alginate nanoparticles embedded polycaprolactone-chitosan nanofibers as a controlled drug delivery nanoplatform for anticancer activity

Nanocarrier-based drug delivery systems have been designed into various structures that can effectively prevent cancer progression and improve the therapeutic cancer index. However, most of these delivery systems are designed to be simple nanostructures with several limitations, including low stability and burst drug release features. A nano-in-nano delivery technique is explored to address the aforementioned concerns. Accordingly, this study investigated the release behavior of a novel nanoparticles-in-nanofibers delivery system composed of capsaicin-loaded alginate nanoparticles embedded in polycaprolactone-chitosan nanofiber mats. First, alginate nanoparticles were prepared with different concentrations of cationic gemini surfactant and using nanoemulsion templates. The optimized formulation of alginate nanoparticles was utilized for loading capsaicin and exhibited a diameter of 19.42 ± 1.8 nm and encapsulation efficiency of 98.7 % ± 0.6 %. Likewise, blend polycaprolactone-chitosan nanofibers were prepared with different blend ratios of their solutions (i.e., 100:0, 80:20, 60:40) by electrospinning method. After the characterization of electrospun mats, the optimal nanofibers were employed for embedding capsaicin-loaded alginate nanoparticles. Our findings revealed that embedding capsaicin-loaded alginate nanoparticles in polycaprolactone-chitosan nanofibers, prolonged capsaicin release from 120 h to more than 500 h. Furthermore, the results of in vitro analysis demonstrated that the designed nanoplatform could effectively inhibit the proliferation of MCF-7 human breast cells while being nontoxic to human dermal fibroblasts (HDF). Collectively, the prepared nanocomposite drug delivery platform might be promising for the long-term and controlled release of capsaicin for the prevention and treatment of cancer.

Antifouling improvement in Pb2+ ion selective electrodes by using an environmentally friendly capsaicin derivative

Biofouling is a critical issue for ion selective electrodes (ISE) in complex aqueous systems, seriously compromising the analytical performance of the electrodes (i.e., stability, sensitivity, and lifetime). Herein, an antifouling solid lead ion selective electrode (GC/PANI-PFOA/Pb²⁺-PISM) was successfully prepared by adding propyl 2-(acrylamidomethyl)-3,4,5-trihydroxy benzoate (PAMTB), an environmentally friendly capsaicin derivative, into the ion-selective membrane (ISM). The presence of PAMTB caused no loss in the detection performance of GC/PANI-PFOA/Pb²⁺-PISM (e.g., detection limit (1.9 × 10^-7 M), response slope (28.5 ± 0.8 mV/decade), the response time (20 s), stability (8.6 ± 2.9 μV/s), selectivity and no water layer), whilst imparting an excellent antifouling effect with an antibacterial rate of 98.1% when the content of PAMTB in the ISM was 2.5 wt%. Further, GC/PANI-PFOA/Pb²⁺-PISM maintained stable antifouling properties, excellent potential response, and stability even after soaking in a high-concentration bacterial suspension for 7 days.

Self-polishing antifouling coatings based on benzamide derivatives containing capsaicin

In this study, N-hydroxymethylbenzamide was alkylated with various aromatic compounds to obtain five novel benzamide derivatives containing capsaicin (BDCC), and the BDCC were incorporated into coatings as auxiliary agents. The relationships between properties and structures were discussed based on experimental and theoretical results. The theoretical results showed the optimized configurations of BDCC and confirmed that the benzene ring, phenolic hydroxyl, ester and amide groups were active sites. Experimental results indicated that the antimicrobial and antifouling effects of compounds b1, b2 and b3 were better than those of chlorothalonil, their MIC and MBC values were no more than 64 and 512 μg·mL-1, and their test panels were covered only with small amounts of dirt and biofilms; they worked well as green antifouling additives. The experimental and theoretical results showed that BDCC and BDCC antifouling coatings were effective and eco-friendly.

Capsaicin-Modified Fluorosilicone Based Acrylate Coating for Marine Anti-Biofouling

Capsaicin has been extensively studied for its excellent antifouling activity and very low environmental toxicity. However, mixing natural capsaicin with coatings can cause rapid capsaicin leakage, severely shortening its antifouling cycle. In this study, we describe the preparation and performance of a new capsaicin-modified marine antifouling organofluorosilicone, which is based on silicone and fluorine acrylate monomers covalently bound to an organic antimicrobial monomer, HMBA (N-(4-hydroxy-3-methoxybenzyl)-acrylamide) on a polymer network. The chemical grafting of HMBA into the polymer has improved the problem of short antifouling life of the coating due to antifouling agent leakage and the environmental pollution caused by the leakage. The study focused on the synthesis of pristine acrylate monomers with organic bioactive groups prepared from vanillin amine salts and their co-polymerization in the presence of distal acrylate oligomers. The resulting cross-linked films were characterized using infrared spectroscopy, contact angle, and adhesion analyses. The results indicate that the materials had good adhesion, low surface energy, and were resistant to prolonged immersion in water. The polyacrylate coating synthesized from acrylate exhibited antibacterial and anti-algae activity. Biological tests on the marine microorganisms, Pseudomonas species, Shewanella species, and Navicula incerta, revealed a 97%, 98%, and 99% reduction compared to the blank control group, respectively, indicating that the coating has strong anti-adhesive ability. This work is expected to develop a promising material for marine antifouling.

A review of the catalytic conversion of glycerol to lactic acid in the presence of aqueous base

Lactic acid is a high-value-added chemical with large production, which is used in many industries including the production of pyruvic and acrylic acids. Lactic acid is largely obtained from the oxidation of glycerol, which is a prevalent by-product of biodiesel production. However, the oxidation of glycerol to lactic acid requires harsh reaction conditions such as high temperature and pressure as well as the use of a hefty strong base. In the presence of suitable catalysts, the production of lactic acid from glycerol can be achieved under mild conditions with 1 equivalent base per mole of glycerol. Herein, we review the reports of the catalytic conversion of glycerol to lactic acid in an aqueous alkaline medium considering the reaction conditions, catalytic activity for glycerol conversion and selectivity for lactic acid. We start first with the reports on the use of homogeneous catalysts that have high catalytic activity but miserable recovery. Next, we discuss the employment of colloidal metal(0) nanoparticles as catalysts in glycerol oxidation. The papers on the use of supported metal(0) nanoparticles are reviewed according to the type of support. We then review the polymetallic and metal/metal oxide nanocatalysts used for the conversion of glycerol to lactic acid in an alkaline medium. The catalysts tested for glycerol conversion to lactic acid without any additional bases are also discussed to emphasize the importance of a strong base for catalytic performance. The proposed mechanisms of glycerol oxidation to lactic acid in the presence or absence of catalysts as well as for the formation of side products are discussed. The available experimental kinetics data are shown to fit the mechanism with the formation of glyceraldehyde from glycerol alkoxide as the rate-determining step.

Ultrasound-assisted deep eutectic solvents extraction of glabridin and isoliquiritigenin from Glycyrrhiza glabra: Optimization, extraction mechanism and in vitro bioactivities

Licorice (Glycyrrhiza glabra) is extensively used owing to the superior pharmacological effects. However, its maximum application potential has not been fully exploited due to the limitation of currently available extraction solvent and methods. In this study, an eco-friendly deep eutectic solvent (NADESs) based ultrasound-assisted extraction (DES-UAE) method was applied to prepare licorice extracts. The DES-UAE using choline chloride and lactic acid as solvent was optimized and modeled by using response surface methodology to maximize the extraction yields of glabridin (GLA) and isoliquiritigenin (ISL). The optimized extracts possessed higher contents of GLA and ISL than available extraction methods, and the enriched products showed superior pharmacological activities in vitro. Furthermore, scanning electron microscopy (SEM) and molecular dynamic simulation analyses were performed to deeply investigate the interaction between solvent and targeted compounds. This study not only provides an eco-friendly method for high-efficient extraction of GLA and ISL from licorice but also illustrates the mechanism of the increased extraction efficacy, which may contribute to the application of licorice and deep insight into extraction mechanism using DES.

Antibacterial properties of capsaicin and its derivatives and their potential to fight antibiotic resistance - A literature survey

Antibiotic resistance is endangering public health globally and gives reason for constant fear of virtually intractable bacterial infections. Given a limitation of novel antibiotic classes brought to market in perspective, it is indispensable to explore novel, antibiotics-independent ways to fight bacterial infections. In consequence, the antibacterial properties of natural compounds have gained increasing attention in pharmacological sciences. We here performed a literature survey regarding the antibacterial effects of capsaicin and its derivatives constituting natural compounds of chili peppers. The studies included revealed that the compounds under investigation exerted i.) both direct and indirect antibacterial properties in vitro depending on the applied concentrations and the bacterial strains under investigation; ii.) synergistic antibacterial effects in combination with defined antibiotics; iii.) resistance-modification via inhibition of bacterial efflux pumps; iv.) attenuation of bacterial virulence factor expression; and v.) dampening of pathogen-induced immunopathological responses. In conclusion, capsaicin and its derivatives comprise promising antimicrobial molecules which could complement or replace antibiotic treatment strategies to fight bacterial infections. However, a solid basis for subsequent clinical trials requires future investigations to explore the underlying molecular mechanisms and in particular pharmaceutical evaluations in animal infection models.

Natural capsicum extract replacing chlortetracycline enhances performance via improving digestive enzyme activities, antioxidant capacity, anti-inflammatory function, and gut health in weaned pigs

The objective of this study was to investigate the effects of natural capsicum extract (NCE, containing 2% natural capsaicin, the rest is carrier) replacing chlortetracycline (CTC) on performance, digestive enzyme activities, antioxidant capacity, inflammatory cytokines, and gut health in weaned pigs. A total of 108 weaned pigs (Duroc × [Landrace × Yorkshire], initial body weight = 8.68 ± 1.34 kg; weaned on d 28) were randomly allotted into 3 treatments with 6 replicate pens per treatment (3 barrows and 3 gilts per pen). The treatments include a corn-soybean meal basal diet as a control group (CON), a CTC group (basal diet + CTC at 75 mg/kg), and a NCE group (basal diet + NEC at 80 mg/kg). Compared with CON and CTC, NCE had increased (P < 0.05) average daily gain in phase 2 (d 15 to 28) and overall (d 1 to 28), and higher (P < 0.05) apparent total tract digestibility of gross energy, dry matter, crude protein, and organic matter in phase 1 (d 1 to 14). These pigs also had increased (P < 0.05) pancrelipase activity in pancreas, α-amylase, lipase and protease activities in the jejunal mucosa, and lipase activity in the ileal mucosa on d 28. Moreover, NCE had increased (P < 0.05) the contents of growth hormone, β-endorphin, 5-hydroxytryptamine, total antioxidant capacity, total superoxide dismutase, catalase, and IL-10, as well as decreased (P < 0.05) contents of malondialdehyde, tumor nuclear factor-α, interferon-γ, and interleukin-6 in serum on d 28 compared with CON and CTC. NCE showed higher (P < 0.05) propionic acid, butyric acid and total volatile fatty acids (VFA) contents, and increased (P < 0.05) relative abundance of Faecalibacterium in colon, as well as higher (P < 0.05) propionic acid and total volatile fatty acids in cecum on d 28 compared with CON. In conclusion, NCE replacing CTC could enhance performance via improving digestive enzyme activities, antioxidant capacity, anti-inflammatory function, gut VFA composition and microbiota community in weaned pigs, and it could be used as a potential target for the development of feed additives.

Preparation and Evaluation of Gallate Ester Derivatives Used as Promising Antioxidant and Antibacterial Inhibitors

Many gallate esters have been applied as food additives due to their good biological properties. Herein, nine novel gallate ester derivatives were synthesized by a Friedel-Crafts alkylation reaction and characterized by melting point (m.p.), infrared (IR) spectroscopy, nuclear magnetic resonance (¹ H- and ¹³ C-NMR) spectra, and high-resolution mass spectrometry (HR-ESI-MS). Their antioxidant and antibacterial activities were measured using a series of classical assays. Studies found that the products showed favorable antioxidant and antibacterial activities. Their 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH^⋅ ) scavenging effect IC₅₀ values were less than 5.00 μg mL^-1 and their reducing power was not less than that of vitamin C (Vc). Furthermore, the antibacterial results showed that the minimum inhibitory concentration (MIC) values of the products were not greater than 8.00 μg mL^-1 , and their antibacterial rates were over 95 % at 300 μg mL^-1 . The above data add valuable and novel information that gallate ester derivatives can be considered potential food additives to address food safety issues because of their high biological activity and health benefits.