Natural Antimicrobials Research Articles

Characterization of free radical-mediated Pleurotus ostreatus polysaccharide-EGCG conjugates for chilled minced pork preservation

To improve the functions of Pleurotus ostreatus polysaccharide (POP), POP-EGCG conjugates were prepared using free radical graft polymerization reactions and were characterized using UV–vis, FT-IR, SEM, XRD, DSC, TG, particle size and potential, three-phase contact angle, and rheological tests; The antioxidant and antibacterial ability in vitro were detected. Moreover, effects of POP-EGCG on the quality of refrigerated minced pork were investigated. The results showed the optimal preparation conditions of POP-EGCG were 1 % POP, 1.3 % EGCG, 0.25 % Vc, 16 % concentration of H2O2, and reaction 17 h. The POP-EGCG showed the characteristic peak of EGCG and was a mesh honeycomb with rough and porous surface; It had higher crystallinity, increased particle size, but decreased thermal stability, solubility, and viscosity, and significantly enhanced antioxidant and antibacterial ability. The POP-EGCG effectively improved the sensory quality and inhibited lipid oxidation of chilled minced pork, and extended the shelf life of minced pork up to 9 days at 4 °C. Specifically, the TVB-N and TBARS of minced pork in the POP-EGCG group were respectively 14.93 mg/100 g and 0.9 mg MDA/kg, which were lower than the spoilage thresholds in the national standard. This study provides a theoretical basis for further development of natural antioxidants and antimicrobial agents.

Analytical and Antimicrobial Characterization of Zn-Modified Clays Embedding Thymol or Carvacrol.

Carvacrol and thymol are broad-spectrum natural antimicrobial agents. To reduce their volatility and improve their antimicrobial performance, synergistic systems were prepared loading the active molecules in zinc-modified clays. Montmorillonite (MMT) and zeolite (ZEO) were modified with zinc ions (ZnMMT and ZnZEO), with well-known antimicrobial properties, and then with carvacrol or thymol, reaching the 26 ± 3% and 33 ± 2% w/w of loading, respectively. The resulting hybrid materials were characterized by FT-IR, XPS, XRD, TGA, and GC-MS to evaluate carvacrol/thymol release in simulating food matrices. Antimicrobial assays carried out using spoiler and pathogenic bacterial strains showed that the antimicrobial activity of both thymol and carvacrol was largely preserved once they were loaded into Zn-modified clays. However, MMT hybrids showed an antibacterial activity significantly higher than ZEO hybrids at 50 mg/mL of thymol and carvacrol. For this reason, deeper antimicrobial evaluations were carried out only for ZnMMT composites. ZnMMT loaded with thymol or carvacrol produced inhibition zones against most of the target strains, also at 3.12 mg/mL, while the positive controls represented by the single molecule thymol or carvacrol were not active. The hybrid materials can be useful for applications in which the antimicrobial activity of natural molecules need to be displayed over time as requested for the control of microbial pathogens and spoilage bacteria in different applications, such as active packaging, biomaterials, and medical devices.

Are Mouthwashes Really Effective against Candida spp.?

Oral candidiasis is an opportunistic infection caused by fungi of the genus Candida. Nystatin, fluconazole, and miconazole are the most widely used antifungal drugs in dentistry, but in recent years, they have been shown to be less effective due to the increase in the resistance to antifungal drugs. The growing challenge of antifungal resistance emphasizes the importance of exploring not only alternative strategies in the fight against Candida spp. infections but also supportive treatment for pharmacological treatment for oral candidiasis. This review aims to evaluate and compare the in vitro reports on antifungal efficacy against Candida spp. exhibited by mouthwashes distributed on the European market. The research question was elaborated through the PEO framework recommended by PRISMA 2020. A bibliographic search strategy was developed for the scientific online databases Pubmed and ScienceDirect. According to the eligibility criteria, 21 papers were included in this study over a 27-year period. Mouthwashes containing chlorhexidine digluconate, cetylpyridinium chloride, hexetidine, and fluorine compounds among others, and natural antimicrobials, such as menthol, thymol, eucalyptol, and Glycyrrhiza glabra extracts, have demonstrated antifungal effectiveness. Nonetheless, the methodological variance introduces ambiguity concerning the comparative efficacy of distinct molecules or mouthwash formulations and complicates the evaluation and the comparison of results between studies. Some mouthwashes commercially available in Europe have the potential to be used in anti-Candida therapy and prevention since they have shown antifungal effect.

Chitosan-coated PLGA microemulsion loaded with tannic acid against Escherichia coli in vitro and in vivo

The overuse of antibiotics has resulted in a surge of drug-resistant bacteria, making the pursuit of natural antimicrobials an urgent and significant trend. Encapsulation and nanoparticulation are effective ways to enhance the antibacterial properties of natural drugs. In this study, we encapsulated tannic acid (TA) with chitosan (CS) and poly (lactide-co-glycolide) (PLGA) using the emulsion-solvent evaporation method to enhance the antimicrobial effect of TA. We prepared a bilayer membrane spherical nanoemulsion of TA-PLGA-CS (TPC) with uniform size of 559.87 ± 1.16 nm, and zeta potential of 59.53 ± 1.07 mV. TPC could be stably stored for 90 days at 4°C without affecting the properties of the emulsion, and the minimum bactericidal concentration against four strains of Escherichia coli (E. coli) remained unchanged for 60 d. The results indicated that TPC enhanced the inhibitory effect of TA against E. coli. Scanning electron microscope images revealed that TPC treatment caused damage to the bacterial cell membrane. In addition, in vivo experiments indicated that TPC exhibited a superior therapeutic effect on artificial colibacillosis in chickens infested with Avian pathogenic Escherichia coli, as evidenced by the changes in body weight and a reduction bacterial load in heart. Furthermore, TPC reversed the down-regulation of catalase, glutathione peroxidase1 (GPX1), and GPX7 gene expression levels in intestinal tissues. Compared to the model group, TPC treatment elevated serum glutathione peroxidase activities and lowered myeloperoxidase and lactate dehydrogenase levels, offering antioxidant protection that was slightly better than that of doxycycline hydrochlorid group. In summary, we prepared a novel TA antimicrobial preparation with significant antioxidant potential and inhibitory effect against E. coli both in vitro and in vivo.

Isolation, characterization, and application of a lytic bacteriophage SSP49 to control Staphylococcus aureus contamination on baby spinach leaves

Staphylococcus aureus, a major foodborne pathogen, is frequently detected in fresh produce. It often causes food poisoning accompanied by abdominal pain, diarrhea, and vomiting. Additionally, the abuse of antibiotics to control S. aureus has resulted in the emergence of antibiotics-resistant bacteria, such as methicillin resistant S. aureus. Therefore, bacteriophage, a natural antimicrobial agent, has been suggested as an alternative to antibiotics. In this study, a lytic phage SSP49 that specifically infects S. aureus was isolated from a sewage sample, and its morphological, biological, and genetic characteristics were determined. We found that phage SSP49 belongs to the Straboviridae family (Caudoviricetes class) and maintained host growth inhibition for 30 h in vitro. In addition, it showed high host specificity and a broad host range against various S. aureus strains. Receptor analysis revealed that phage SSP49 utilized cell wall teichoic acid as a host receptor. Whole genome sequencing revealed that the genome size of SSP49 was 137,283 bp and it contained 191 open reading frames. The genome of phage SSP49 did not contain genes related to lysogen formation, bacterial toxicity, and antibiotic resistance, suggesting its safety in food application. The activity of phage SSP49 was considerably stable under various high temperature and pH conditions. Furthermore, phage SSP49 effectively inhibited S. aureus growth on baby spinach leaves both at 4 °C and 25 °C while maintaining the numbers of active phage during treatments (reductions of 1.2 and 2.1 log CFU/cm2, respectively). Thus, this study demonstrated the potential of phage SSP49 as an alternative natural biocontrol agent against S. aureus contamination in fresh produce.

Effects of Mint Oils on the Human Oral Microbiome: A Pilot Study.

The oral microbiome is a diverse and complex ecosystem essential for maintaining oral and systemic health. Our study is the first to define the oral microbial community in Egyptian young adults and investigate the effects of natural antimicrobials on the oral microbiome. SuperMint (SM) is a proprietary blend of peppermint, Japanese mint, bergamot mint, and spearmint essential oils encapsulated in a tiny soft beadlet. This work aimed to evaluate the effects of SM beadlets on the oral microbiome. This study recruited twenty healthy participants. A baseline investigation of the oral microbiome of the selected participants was performed by collecting saliva and swab samples before treatment. Treatment included chewing four SM beadlets twice a day for 7 days, and then, post-administration saliva and swab samples were collected at the end of treatment. The oral microbiome samples were analyzed by the high-throughput amplicon sequencing of 16S rRNA gene fragments, and the community composition was determined. The results showed that the abundance of some microbial genera and families decreased after using SM, including Prevotella, Streptococcus, Neisseria, and Haemophilus. However, some genera showed inconsistent patterns. We also found that the subject's gender and SM usage were significantly associated with diverse microbial composition. The results suggest that SM treatment decreased the abundance of several bacteria associated with halitosis and periodontal diseases, such as Actinomyces and Streptococcus. Furthermore, Corynebacterium species increased and Streptococcus decreased after SM usage. More research is needed to fully understand the antimicrobial effects of mint oils and their potential applications in maintaining good oral health.

Organic extracts from sustainable hybrid poplar hairy root cultures as potential natural antimicrobial and antibiofilm agents.

In order to meet growing consumer demands in terms of naturalness, the pharmaceutical, food, and cosmetic industries are looking for active molecules of plant origin. In this context, hairy roots are considered a promising biotechnological system for the sustainable production of compounds of interest. Poplars (genus Populus, family Salicaceae) are trees of ecological interest in temperate alluvial forests and are also cultivated for their industrial timber. Poplar trees also produce specialized metabolites with a wide range of bioactive properties. The present study aimed to assess the hybrid poplar hairy root extracts for antimicrobial and antibiofilm activities against four main life-threatening strains of Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. Ethyl acetate extracts from two hairy root lines (HP15-3 and HP A4-12) showed significant antibacterial properties as confirmed by disc diffusion assay. Antibiofilm activities were found to be dose dependent with significant biofilm inhibition (75-95%) recorded at 1000µg.mL-1 in all the bacterial strains tested. Dose-dependent enhancement in the release of exopolysaccharides was observed in response to treatment with extracts, possibly because of stress and bacterial cell death. Fluorescence microscopy confirmed loss of cell viability of treated bacterial cells concomitant with increased production of reactive oxygen species compared to the untreated control. Overall, this study demonstrates for the first time a high potential of poplar hairy root extracts as a natural and safe platform to produce antimicrobial agents in pharmaceutical, food, industrial water management, or cosmetic industries.

Antimicrobial properties of Citrus maxima flavedo extracts against food pathogens and spoilage microorganisms

This study assesses the antimicrobial potential of ethyl acetate and dichloromethane extracts obtained from pomelo, Citrus maxima (C. maxima), flavedo against various food pathogens and spoilage microorganisms. The antimicrobial activities of these extracts were evaluated using the agar disc diffusion method against gram-positive bacteria (Bacillus cereus), Staphylococcus aureus and gram-negative bacteria (Escherichia coli). The results indicated that both extracts demonstrated antibacterial properties against the tested microorganisms. The ethyl acetate extract exhibited significantly higher antibacterial activity against the majority of bacterial strains compared to the dichloromethane extract, particularly against S. aureus and B. cereus. However, dichloromethane extract showed a better effect on E. coli, with the inhibition zone ranging from 8.7 to 11.3 mm. S. aureus displayed the highest sensitivity to ethyl acetate and dichloromethane extracts of pomelo flavedo with inhibition zones ranging from 1.3 to 1.5 mm, respectively. In conclusion, the findings suggest that pomelo extracts have significant potential as natural antimicrobials and can be safely utilized as food preservatives. This highlights the value of pomelo as a potential source of antimicrobial compounds for food safety and preservation purposes.

Cellulose‐enriched ascorbic acid for wound dressing application: Future medical textile

AbstractWounds infected by resistant microbes have become a cost and health problem worldwide. In modern wound care, healing mechanisms require particular strategies, such as adding natural antioxidants and antimicrobials in a biocompatible biopolymer matrix mimicking extracellular tissue such as cellulose. Here, ascorbic acid or Vitamin C is a promising bioactive as a topical drug loaded in a cellulose‐based composite matrix for skin tissue repair. Ascorbic acid, cellulose, or cellulose composites enriched with ascorbic acid have shown better biocompatibility and biological effects for accelerating wound healing, making them promising as sustainable medical textiles. Future challenges relate to the ideal engineered wound dressing design, raw material toxicity, and 3D printing technology.

Enhancing antibacterial efficacy through propolis-infused electroactive polymers: A novel approach to combat antibiotic resistance

The increasing prevalence of antibiotic-resistant illnesses worldwide calls for the development of novel antibacterial strategies, including the ones based on antibacterials materials. This work reports on the combined antibacterial effects of piezoelectric poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) and propolis, a natural antimicrobial agent, on various material structures (2D films and 3D structures) to increase the surface contact area. It is shown that the addition of propolis has a substantial impact on the surface texture and mechanical properties of the materials. In particular, 3D structures exhibit improved distribution of propolis and enhanced mechanical stability in comparison to 2D films. The antibacterial experiments conducted on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) demonstrate a significant increase in the reduction of bacteria, in particular when larger concentrations of propolis are applied and when mechanical stimulation is used at specified frequencies, taking therefore advantage of the surface charge variation associated to the piezoelectric response. It is particularly significant the antibacterial effect on the resistant S.aureus bacteria, emphasising the huge potential of this novel hybrid material in biomedical applications. Thus, it is demonstrated that piezoelectric polymers in combination with natural antibacterial agents, represents a suitable approach to address microbial resistance, with important applications in areas including wound dressings, implant coatings, and high traffic surfaces, among others.

The study of honokiol as a natural product-based antimicrobial agent and its potential interaction with FtsZ protein.

Multidrug resistant bacteria have been a global health threat currently and frontline clinical treatments for these infections are very limited. To develop potent antibacterial agents with new bactericidal mechanisms is thus needed urgently to address this critical antibiotic resistance challenge. Natural products are a treasure of small molecules with high bioactive and low toxicity. In the present study, we demonstrated that a natural compound, honokiol, showed potent antibacterial activity against a number of Gram-positive bacteria including MRSA and VRE. Moreover, honokiol in combination with clinically used β-lactam antibiotics exhibits strong synergistic antimicrobial effects against drug-resistant S. aureus strains. Biochemical studies further reveal that honokiol may disrupt the GTPase activity, FtsZ polymerization, cell division. These biological impacts induced by honokiol may ultimately cause bacterial cell death. The in vivo antibacterial activity of honokiol against S. aureus infection was also verified with a biological model of G. mellonella larvae. The in vivo results support that honokiol is low toxic against the larvae and effectively increases the survival rate of the larvae infected with S. aureus. These findings demonstrate the potential of honokiol for further structural advancement as a new class of antibacterial agents with high potency against multidrug-resistant bacteria.

Phytochemicals and Antibiotic Studies of Ethanolic Extracts of Dennettia Tripetala (Mmimi/Pepper Fruit) and Psidium Guajava (Guava) Leaves on Clinical Isolates of Staphylococcus Aureus and Escherichia Coli

Aqueous and ethanolic leaf extracts of Dennetia tripetala and Psidium guajava were evaluated for their antimicrobial effects against clinical isolates of Staphylococcus aureus and Escherichia coli from Annunciation Specialist Hospital Enugu State Nigeria. The identified isolates were sub-cultured on sterile nutrient agar plates and incubated over night at 37°C. The identified isolates were then re-identified and characterized. Polymerase chain reaction (PCR) was used to detect Staphylococcus aureus strain which has 85% pairwise similarity with Staphylococcus haemolyticus strain SH1 and Escherichia coli strain which has 99.62% pairwise similarity with E. coli strain AC1. Quantitative and qualitative phytochemical analysis were done on the extracts of Dennetia tripetala and Psidium guajava using water and ethanol as extracting solvents. The phytochemical screening of the extracts revealed the presence of tannins, saponins, alkaloids, flavonoids, glycosides and phenols. Quinonas however, was absent in this study. The isolates were screened for sensitivity to different extracts using agar well diffusion technique. The results indicated that both the ethanol and aqueous extracts of the Psidium guajava leaves showed inhibitory activity against Staphylococcus aureus at 10mm and 12mm respectively but no activity against E. coli. On the other hand, the aqueous extracts of the Dennetia tripetala showed inhibitory activity against S. aureus and E. coli at 20mm and 10mm respectively whereas, the ethanol extract has no activity on both test microorganism. The extracts were reconstituted with Dimethyl sulfoxide (DMSO) to concentrations (mg/ml) of 200, 100, 50, 25, 12.5 and the minimal inhibitory concentration (MIC) of the extracts were determined using agar well method. The MIC of the Psidium guajava leaves extract revealed that both ethanolic and aqueous extracts inhibited S. aureus at 12.5mg/ml. While MIC of the Dennetia tripetala revealed that the aquous extract inhibited S. aureus at 50mg/ml and E. coli at 100mg/ml from the results, the aqueous extracts of both plants generally have a better inhibitory property than the ethanolic extracts. Based on the present findings, Dennetia tripetala and Psidium guajava leaves possess the capability of being good candidates in the search for a natural antimicrobial agent against infections or diseases caused by Staphylococcus aureus and Escherichia coli.

A new application of avocado oil to enrich the biological activities of polycaprolactone membranes for tissue engineering.

The metabolites synthesized by plants to protect themselves serves as natural antimicrobial agents used in biomaterials. In this study, avocado oil (AO), was incorporated as a plant source and natural antimicrobial agent into polycaprolactone (PCL) membranes. The effects of varying AO ratios (25, 50, and 100 wt%.-PCL@25AO, PCL@50AO, PCL@100AO) on PCL membrane morphology, chemical structure, wettability, antimicrobial activity, and cell viabilities were investigated. It was demonstrated that the AO acts as a pore-forming agent in solvent-casted membranes. Young's modulus of the membranes varied between 602.68 and 31.92 MPa and more flexible membranes were obtained with increasing AO content. Inhibition zones of AO were recorded between 7.86 and 13.97 mm against clinically relevant microbial strains including bacteria, yeast, and fungi. Antimicrobial activity of AO was retained in PCL membranes at all ratios. Resazurin assay indicated that PCL@25AO membranes were cytocompatible with mouse fibroblast cells (L929 cell line) on day 6 showing 72.4% cell viability with respect to neat PCL membranes. Viability results were supported by scanning electron microscopy images and DAPI staining. The overall results of this study highlight the potential of PCL@25AO membranes as a biomaterial with antimicrobial properties, cytocompatibility, and mechanical strength suitable for various biomedical applications.

Ratanjot (Alkanna tinctoria L.) Root Extract, Rich in Antioxidants, Exhibits Strong Antimicrobial Activity against Foodborne Pathogens and Is a Potential Food Preservative.

Natural and sustainable plant-based antioxidants and antimicrobials are highly desirable for improving food quality and safety. The present investigation assessed the antimicrobial and antioxidant properties of active components from Alkanna tinctoria L. (herb) roots, also known as Ratanjot root. Two methods were used to extract active components: microwave-assisted hot water (MAHW) and ethanolic extraction. MAHW extract yielded 6.29%, while the ethanol extract yielded 18.27%, suggesting superior Ratanjot root extract powder (RRP) solubility in ethanol over water. The ethanol extract showed significantly higher antioxidant activity than the MAHW extract. Gas Chromatography-Mass Spectrometry analysis revealed three major phenolic compounds: butanoic acid, 3-hydroxy-3-methyl-; arnebin 7, and diisooctyl pthalate. The color attributes (L*, a*, b*, H°ab, C*ab) for the ethanolic and MAHW extracts revealed significant differences (p < 0.05) in all the above parameters for both types of extracts, except for yellowness (b*) and chroma (C*ab) values. The ethanol extract exhibited antimicrobial activity against 14 foodborne bacteria, with a significantly higher inhibitory effect against Gram-positive bacteria (Listeria monocytogenes and Staphylococcus aureus) than the Gram-negative bacteria (Salmonella enterica serovar Typhimurium and Escherichia coli). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were both 25 mg/mL for the Gram-negative bacteria, while the MIC and MBC concentrations varied for Gram-positive bacteria (0.049-0.098 mg/mL and 0.098-0.195 mg/mL) and the antimicrobial effect was bactericidal. The antimicrobial activities of RRP extract remained stable under broad temperature (37-100 °C) and pH (2-6) conditions, as well as during refrigerated storage for 30 days. Application of RRP at 1% (10 mg/g) and 2.5% (25 mg/g) levels in a cooked chicken meatball model system prevented lipid oxidation and improved sensory attributes and retarded microbial growth during refrigerated (4 °C) storage for 20 days. Furthermore, the RRP extract was non-toxic when tested with sheep erythrocytes and did not inhibit the growth of probiotics, Lacticaseibacillus casei, and Lactiplantibacillus plantarum. In conclusion, the study suggests that RRP possesses excellent antimicrobial and antioxidant activities, thus making it suitable for food preservation.

In vitro antibacterial and antifungal potentials of Ocimum tenuiflorum and Ocimum gratissimum essential oil

IntroductionOcimum known as Tulsi has various health benefits mentioned in Ayurveda. Ocimum polysaccharides are used in pharmacology as the capacity to prevent ageing, boost immunity, suppress tumor growth, reduce diabetes mellitus and function as an antioxidant. Therefore, the goal of the current investigation was to examine the antibacterial and antifungal activities of Ocimum tenuiflorum and Ocimum gratissimum essential oils. MethodEssential oils of Ocimum tenuiflorum and Ocimum gratissimum were extracted by hydrodistillation method and antibacterial and antifungal activities were done by agar well diffusion and broth micro dilution method. Furthermore, In silico toxicity analysis was done by the SwissADME server. ResultOcimum gratissimum essential oil was found to have an extraction yield of 2.75 ± 0.5 % and 3.90 ± 0.5 % for O. tenuiflorum. α-thujene (15.33 %), eugenol (16.11 %) and β-terpineol (7.75 %) were the major phytocompounds of O. tenuiflorum whereas chavibetol (17.70), α-pinene (15.16 %) and bicyclosesquiphellandrene (9.07 %) were the major phytocompounds of O. gratissimum essential oil. Forging ahead, essential oil of O. tenuiflorum showed MIC of 0.078 % against E. coli ATCC29213, 0.3125 % against K. pneumoniae MTCC39, 0.078 % against S. aureus ATCC25922, 0.625 % against both C. albicans, MTCC277 and ATCC90028, however, essential oil of O. gratissimum showed MIC of 1.25 % against E. coli ATCC29213, followed by K. pneumonia MTCC39 (2.5 %) and S. aureus ATCC25922 (2.5 %) and 5.0 % against both C. albicans MTCC277 and ATCC90028. Certainly, phytocompounds of both the Ocimum spp. also fulfilled the Lipinski rule and showed characteristics similar to drugs. β-terpinole demonstrated the best antibacterial activity with a Pa value of 0610 and β-caryophyllene and caryophyllene oxide had the best antifungal activity with a Pa value of 0647. ConclusionTo conclude, the current study showed that O. tenuiflorum and O. gratissimum have good antibacterial and antifungal activity and on the basis of further experimentation, can be used as a source of natural antimicrobials.

Rosa × damascena Herrm. From Azaran region, Kashan: rich in saturated and unsaturated fatty acids with inhibitory effect against Proteus mirabilis

BackgroundOne of the most widely used medicinal plants in Iranian traditional medicine, Rosa × damascena Herrm. (mohammadi flower) that the people of Kashan use as a sedative and to treat nervous diseases and constipation. In this research, the yield, chemical composition and antimicrobial activity of the essential oil of this plant were evaluated for the first time from Azaran region, Kashan.MethodsThe essential oil was extracted by means of hydrodistillation (Clevenger), and its chemical compounds were identified and determined by GC/MS. The antimicrobial activity of the essential oil was determined by the diffusion method in agar, the minimum growth inhibitory concentration (MIC) and the minimum concentration capable of killing bacterial/fungal microorganisms (MBC/MFC).ResultsThe results showed that the yield of essential oil was 0.1586 ± 0.0331% (w/w). Based on the results of the chemical composition analysis of R. x damascena essential oil, 19 different compounds (98.96%) were identified. The dominant and main components of the essential oil were oleic acid (48.08%), palmitic acid (15.44%), stearic acid (10.17%), citronellol (7.37%) and nonadecane (3.70%). Based on the results of diffusion in agar, the highest zone of inhibition against Candida albicans (ATCC 10231) was ~ 9.5 mm. The strongest inhibitory activity of R. x damascena essential oil against Gram-negative Proteus mirabilis (ATCC 43071) was with the diameter of the inhibition zone (~ 9 mm), which was equal to the strength of rifampin (~ 9 mm).ConclusionTherefore, this essential oil is a promising natural option rich in fatty acids, which can be a potential for the production of natural antimicrobials against infectious diseases, especially urinary tract infections.

Analysis of gauze pad made from coconut tree fiber infused with guava derived phenolic compounds

Abstract Gauze pad wound dressing plays a crucial role in protecting the wound and preventing it from factors that can prolong the healing process. However, due to the porous nature of gauze pads, it cannot completely block microbes from getting into the wound. This study analyzes coconut tree fiber as a gauze pad infused with guava derived phenolic compounds, known for its antimicrobial and antioxidant properties. The research assesses the extract’s effectiveness, focusing on phenolic compounds, antioxidant properties, and antimicrobial effects. By employing the disk diffusion method against Staphylococcus aureus, the study reveals that both 50% and 30% extracts exhibit inhibitory activity, with mean zones of inhibition at 8.5 mm and 8.33 mm, respectively, showing the antimicrobial property for both 50% and 30% extracts. The samples also demonstrated notable DPPH radical scavenging capacities for concentrations ranging from 0.006 to 1.27 (%w/v) for the 50% extract sample and from 0.006 to 1.25 for the 30% extract sample, ranging from 1.98% to 68.5% and 7.94% to 69.5%, respectively, indicating antioxidant property for both samples. The researchers have determined that there is no significant difference (p-value = 0.9187, α = 0.05) between the scavenging activity of both 50% and 30% extract. Furthermore, a minimal disparity in total phenolics was observed, with the former containing 1.25 and the latter 1.24 weight percent gallic acid. To determine if there is any negative skin reaction, a patch test was conducted in collaboration with a dermatologist using Stanford Health Care Medicine Standard. The test revealed no adverse skin reactions after three days of no removal usage of the coconut tree fiber gauze pad infused with phenolic compounds, as compared to a commercially available gauze pad. This study underscores the promise of guava extract and its antibacterial properties, particularly against skin pathogens, and its safe application when integrated with coconut fiber. This combination holds potential as a natural antimicrobial agent with diverse applications.

Enhanced antimicrobial potency and stability of juglone/β-cyclodextrin inclusion complexes: a comparative study of formulation methods

Juglone (5-hydroxy-1,4-naphthoquinone), a natural antifungal and antibacterial agent derived from walnut trees, possesses significant therapeutic potential limited by its low water solubility and instability in varying pH and temperature conditions This study aims to address these limitations by enhancing juglone’s solubility, stability, and antimicrobial efficacy through the formation of inclusion complexes with β-cyclodextrin (β-CD). Employing methods such as co-precipitation, freeze-drying, and solvent evaporation, we synthesized these complexes and confirmed their formation using UV–vis, and FT-IR spectroscopy. The obtained optimum complex was characterized using SEM to reveal its structural properties, while NMR analysis showed significant chemical shift changes, indicative of complex formation between juglone and β-CD; additionally, XRD analysis confirmed the amorphous nature of the J-β-CD3-4 inclusion complex, providing direct evidence for its formation. Our findings reveal a notable enhancement in the pH and thermal stability of juglone within the β-CD inclusion complex, in comparison to its free form. Moreover, the antimicrobial activity of the juglone-β-CD complex surpassed that of juglone alone. The increased water solubility of juglone in the inclusion complex contributed to its enhanced antimicrobial activity. The inhibition zone diameters of J-β-CD3-4 inclusion complex against E. coli, S. aureus, and C. albicans were 7, 22, and 8.5 mm, respectively, relatively higher than juglone. Remarkably, in the broth microdluation method, the MIC and MBC values of the inclusion complex were determined to be much lower than those of free juglone, a significant fourfold decrease for S. aureus, and C. albicans and twofold for E. coli. These results underscore the potential of juglone-β-CD complexation in extending the applicability of juglone, especially in sectors such as food preservation, agriculture, and pharmaceuticals, where enhanced stability and efficacy of natural antimicrobial agents are crucial.

Antimicrobial activity of magnolol against Bacillus cereus and its application as food preservative

The aim of this study was to explore the antibacterial properties and mechanism of magnolol against Bacillus cereus. Our findings demonstrated that magnolol exhibited potent antimicrobial activity against B. cereus, with minimum inhibitory concentrations (MICs) of 2 μg/mL. Additionally, magnolol could inhibit spore germination and biofilm formation in a dose-dependent manner. Electron microscopy and membrane potential analysis indicated that the cytomembranes were disrupted, resulting in leakage of cellular contents. Transcriptomic profiling showed that magnolol treatment (1/2 × MIC) resulted in 585 differentially expressed genes (DEGs), including 295 down-regulated and 290 up-regulated genes. Bioinformatic analysis indicated that magnolol affected many potential cellular responses, including cellular metabolic process, locomotion, oxidative stress, and cell membranes. The pathway analysis revealed that DEGs mainly associated with flagellar assembly, bacterial chemotaxis, amino acids, and energy metabolism. Moreover, magnolol obviously reduced the amount of B. cereus in boiled rice and beef at 4 °C storage. These results provided insights into the molecular mechanism of magnolol against B. cereus and suggested that magnolol might be a promising natural antimicrobial agent for controlling the B. cereus in foods. Industrial relevanceBacillus cereus is considered as an important foodborne pathogenic microorganism that can exist as vegetative cells, spores, and biofilm in various food-processing environment, posing a big challenge for the food industry. Magnolol is a natural compound with potent antimicrobial activity against various pathogens and has been certified as safe by food safety organizations. Consequently, magnolol holds great promise as a natural antimicrobial agent for controlling B. cereus contaminations in foods.

Encapsulated pomegranate peel extract as a potential antimicrobial ingredient from food waste.

Pomegranate peel waste is a valuable reservoir of heat-sensitive total hydrolysable tannins (THT), with potential applications in food and pharmaceuticals. Preserving THT is challenging due to degradation post-extraction. We explore ionic gelation as an encapsulation method to optimize THT utilization. Through external gelation, we optimized the process variables using Box-Behnken design. At 40 g kg-1 sodium alginate, 25 g kg-1 calcium chloride, and 300 g kg-1 pomegranate peel extract (PPE), we achieved an 83.65% encapsulation efficiency. Compared to spray drying, external gelation demonstrated superior performance, with enhanced release percentages and stability. Physical, phytochemical, and release profiles of encapsulates were extensively analysed. External gelation achieved an 87.5% release in 30 min, outperforming spray-dried counterparts (69.7% in 25 min). Encapsulated PPE exhibited robust antibacterial activity against Staphylococcus aureus (ATCC 25923) in powdered infant formula, with a 32 ± 0.01 mm zone of inhibition and 300 μg mL-1 minimum inhibitory concentration. Insights into S. aureus growth curves underlined the mechanism of action via membrane potential alterations. The results of carried investigations also showed that the antibacterial activity of the encapsulated PPE extracts against the targeted organism was identical to the antibacterial activity exhibited by synthetic antibiotics used generally to kill microorganisms in food. Therefore, from the findings, it can be concluded that the PPE encapsulate produced using the external gelation technique at the optimized condition displayed superior storage stability possessing strong antimicrobial activity when compared to encapsulate produced using the spray drying technique. External gelation emerges as a potent technique for developing effective encapsulates enriched with natural antimicrobials or antibiotics. This approach holds promise for applications in food, pharmaceuticals, and nutraceuticals, enhancing stability and efficacy while reducing reliance on synthetic antibiotics. © 2024 Society of Chemical Industry.