Antibacterial Activity of H elichrysum italicum Oil on Vegetables and Its Mechanism of Action

Antibacterial and Antifungal Potential of Helichrysum italicum (Roth) G. Don Essential Oil

Helichrysum italicum (Roth) G. Don is a typical Mediterranean plant, with limited distribution on the islands of Sardinia, Corsica, and the Iberian Peninsula, as well as the islands of the Adriatic Sea and the Balkan Peninsula. In these regions, H. italicum is mainly collected from spontaneous nature, while in recent years, there has been a pronounced cultivation trend due to increased demand and market requirements for constant quality of raw materials. Bearing in mind that biological activity is linked with chemical composition, this review aimed to collect data from different scientific databases (Scopus, PubMed, Web of Science, and Google Scholar) on the antimicrobial activity of essential oil and its chemical composition. A total of 20 papers investigating the antibacterial, antibiofilm, and antifungal activities of H. italicum essential oil were found. Furthermore, in these samples, several compounds occurred as dominant: neryl acetate, α-pinene, and γ-curcumene. These compounds are known for their antimicrobial properties, which likely contribute to the essential oil's efficacy against various microbial strains.

Combination of Chromatographic Analysis and Chemometric Methods with Bioactivity Evaluation of the Antibacterial Properties of Helichrysum italicum Essential Oil

Helichrysum italicum (immortelle) essential oil is one of the most popular essential oils worldwide and it has many beneficial properties, including antimicrobial. However, in this plant, the chemical diversity of the essential oil is very pronounced. The aim of this work was to process the GC-MS results of four samples of H. italicum essential oil of Serbian origin by chemometric tools, and evaluate the antimicrobial activity in vitro and in silico. Overall, 47 compounds were identified, the most abundant were γ-curcumene, α-pinene, and ar-curcumene, followed by α-ylangene, neryl acetate, trans-caryophyllene, italicene, α-selinene, limonene, and italidiones. Although the four samples of H. italicum essential oil used in this study were obtained from different producers in Serbia, they belong to the type of essential oil rich in sesquiterpenes (γ-curcumene and ar-curcumene chemotype). In vitro antimicrobial potential showed that five were sensitive among ten strains of tested microorganisms: Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Saccharomyces cerevisiae, and Candida albicans. Therefore, these microorganism models were used further for in silico molecular docking through the mechanism of ATP-ase inhibitory activity. Results showed that among all compounds from H. italicum essential oil, neryl acetate has the highest predicted binding energy. Artificial neural network modeling (ANN) showed that two major compounds γ-curcumene and α-pinene, as well as minor compounds such as trans-β-ocimene, terpinolene, terpinene-4-ol, isoitalicene, italicene, cis-α-bergamotene, trans-α-bergamotene, italidiones, trans-β-farnesene, γ-selinene, β-selinene, α-selinene, and guaiol are responsible for the antimicrobial activity of H. italicum essential oil. The results of this study indicate that H. italicum essential oil samples rich in γ-curcumene, α-pinene, and ar-curcumene cultivated in Serbia (Balkan) have antimicrobial potential both in vitro and in silico. In addition, according to ANN modeling, the proportion of neryl acetate and other compounds detected in these samples has the potential to exhibit antimicrobial activity.

2,4-Diacetylphloroglucinol (DAPG) derivatives rapidly eradicate methicillin-resistant staphylococcus aureus without resistance development by disrupting membrane

Methicillin-resistant Staphylococcus aureus (MRSA) causes severe public health challenges throughout the world, and the multi-drug resistance (MDR) of MRSA to antibiotics necessitates the development of more effective antibiotics. Natural 2,4-diacetylphloroglucinol (DAPG), produced by Pseudomonas, displays moderate inhibitory activity against MRSA. A series of DAPG derivatives was synthesized and evaluated for their antibacterial activities, and some showed excellent activities (MRSA MIC = 0.5-2 μg/mL). Among these derivatives, 7g demonstrated strong antibacterial activity without resistance development over two months. Mechanistic studies suggest that 7g asserted its activity by targeting bacterial cell membranes. In addition, 7g exhibited significant synergistic antibacterial effects with oxacillin both in vitro and in vivo, with a tendency to eradicate MRSA biofilms. 7g is a promising lead for the treatment of MRSA.

Multi-target antibacterial mechanism of ruthenium polypyridine complexes with anthraquinone groups against Staphylococcus aureus

Three new Ru(ii) complexes, [Ru(dtb)2PPAD](PF6)2 (Ru-1), [Ru(dmob)2PPAD](PF6)2 (Ru-2) and [Ru(bpy)2PPAD](PF6)2 (Ru-3) (dtb = 4,4'-di-tert-butyl-2,2'-bipyridine, dmob = 4,4'-dimethyl-2,2'-bipyridine, bpy = 2,2'-bipyridine and PPAD = 2-(pyridine-3-yl)-1H-imidazo[4,5f][1.10]phenanthracene-9,10-dione), were synthesized and characterized by 1H NMR and 13C NMR spectroscopy, HRMS and HPLC. Among them, Ru-1 showed excellent antimicrobial activity against Gram-positive bacteria Staphylococcus aureus (minimum inhibitory concentration (MIC) = 1 μg mL-1) and low hemolytic and cytotoxic activity. In addition, Ru-1 showed obviously rapid bactericidal activity, low resistance rate, bacterial biofilm destroying activity and high biosafety in vivo. Moreover, skin infection models and a mouse model of sepsis indicated that the anti-infective efficacy of Ru-1 was comparable to that of vancomycin. Mechanism exploration results showed that the antibacterial behavior is probably related with targeting of the bacterial cell membrane and inhibiting topoisomerase I.

Sequence Characterization of ITS Regions of Immortelle Helichrysum italicum (Roth) G. Don from the East Adriatic Coast

The immortelle (Helichrysum italicum (Roth) G. Don) is a typical perennial plant of natural vegetation in the Mediterranean region, and due to secondary metabolites with several biological properties (anti-inflammatory, antioxidant, antimicrobial, and anti-proliferative), it has become an important species for essential oil production, especially in the cosmetic industry. To increase the production of highly priced essential oils, it has been moved to cultivated fields. However, due to the lack of highly characterized planting material, there is a great need for genotype identification, and to provide a link with chemical profiles and geographic origin as a basis for the identification of local superior genotypes. The aims of the study were to characterize the ITS (ribosomal internal transcribed spacer) regions, ITS1 and ITS2, in samples from the East Adriatic region to determine the possibility of using these regions for plant genetic resources identification. Genetic variation was observed when comparing the ITS sequence variants of samples from the North-East Adriatic and the South-East Adriatic. Some rare and unique ITS sequence variants can be helpful for identifying specific populations from different geographical regions.

Helichrysum italicum: From Extraction, Distillation, and Encapsulation Techniques to Beneficial Health Effects

Helichrysum italicum (family Asteraceae), due to its various beneficial health effects, represents an important plant in the traditional medicine of Mediterranean countries. Currently, there is a renewed interest in this medicinal plant, especially in investigations involving the isolation and identification of its bioactive compounds from extracts and essential oils, as well as in experimental validation of their pharmacological activities. In this paper, we review the current knowledge on the beneficial health effects of Helichrysum italicum extracts, essential oils, and their major bioactive polyphenolic compounds, ranging from antioxidative, anti-inflammatory, and anticarcinogenic activities to their antiviral, antimicrobial, insecticidal, and antiparasitic effects. This review also provides an overview of the most promising extraction and distillation techniques for obtaining high-quality extracts and essential oils from Helichrysum italicum, as well as methods for determining their antioxidative, antimicrobial, anti-inflammatory, and anticarcinogenic activities. Finally, new ideas for in silico studies of molecular mechanisms of bioactive polyphenols from Helichrysum italicum, together with novel suggestions for their improved bioavailability through diverse encapsulation techniques, are introduced.

Ruthenium polypyridine complexes with triphenylamine groups as antibacterial agents against Staphylococcus aureus with membrane-disruptive mechanism

Due to the emergence and wide spread of methicillin-resistant Staphylococcus aureus, the treatment of this kind of infection becomes more and more difficult. To solve the problem of drug resistance, it is urgent to develop new antibiotics to avoid the most serious situation of no drug available. Three new Ru complexes [Ru (dmob)₂PMA] (PF6)₂ (Ru-1) [Ru (bpy)₂PMA] (PF6)₂ (Ru-2) and [Ru (dmb)₂PMA] (PF6)₂ (Ru-3) (dmob = 4,4′-dimethoxy-2,2′-bipyridine, bpy = 2,2′-bipyridine, dmb = 4,4′-dimethyl-2,2′-bipyridine and PMA = N-(4-(1H-imidazo [4,5-f] [1,10] phenanthrolin-2-yl) -4-methyl-N-(p-tolyl) aniline) were synthesized and characterized by 1H NMR, 13C NMR and HRMS. The detailed molecular structure of Ru-3 was determined by single crystal X-ray diffraction. Their antibacterial activities against Staphylococcus aureus (Staphylococcus aureus) were obvious and Ru-3 showed the best antibacterial effect with the minimum inhibitory concentration value of 4 μg ml⁻¹. Therefore, further study on its biological activity showed that Ru-3 can effectively inhibit the formation of biofilm and destroy cell membrane. In vitro hemolysis test showed that Ru-3 has almost negligible cytotoxicity to mammalian red blood cells. In the toxicity test of wax moth insect model, Ru-3 exhibited low toxicity in vivo. These results, combined with histopathological studies, strongly suggest that Ru-3 was almost non-toxic. In addition, the synergistic effect of Ru-3 with common antibiotics such as ampicillin, chloramphenicol, tetracycline, kanamycin and gentamicin on Staphylococcus aureus was detected by chessboard method. Finally, in vivo results revealed that Ru-3 could obviously promote the wound healing of Staphylococcus aureus infected mice.

Immortelle (Helichrysum italicum (Roth) G. Don) Essential Oil Showed Antibacterial and Biofilm Inhibitory Activity against Respiratory Tract Pathogens

The biofilm formation of bacteria in different parts of the human body can influence the success of antibiotic therapy. Essential oils (EOs) and their components are becoming increasingly popular in point of view of medicinal applications, because of their antibacterial efficacy. The immortelle EO has been used traditionally as an expectorant; however, there are no studies summarizing its antibacterial effect against respiratory tract bacteria. Our aim was to investigate the antibacterial and biofilm inhibitory activity of immortelle (Helichrysum italicum) EO against respiratory tract pathogens such as Haemophilus influenzae, H. parainfluenzae, Pseudomonas aeruginosa and Streptococcus pneumoniae. In order to prove the antibacterial effect of the immortelle EO, broth microdilution and biofilm inhibition tests, and membrane damage assay were investigated. Scanning electron microscopy was used to identify the structural modifications in bacterial cells. Our results showed that immortelle EO has antibacterial and anti-biofilm effects against respiratory tract bacteria used in this study. H. parainfluenzae was the most sensitive to each treatment, however, P. aeruginosa was the most resistant bacteria. In conclusion, the studied EO may have a role in the treatment of respiratory tract infections due to their antibacterial and anti-biofilm activity.

The Antimicrobial and Antibiofilm Activity of Oregano Essential Oil against Enterococcus faecalis and Its Application in Chicken Breast

Oregano essential oil (OEO) possesses anti-inflammatory, antioxidant, and cancer-suppressive properties. Enterococcus faecalis is a foodborne opportunistic pathogen that can be found in nature and the food processing industry. The goal of this investigation was to explore the antimicrobial action and mechanism of OEO against E. faecalis, inactivation action of OEO on E. faecalis in mature biofilms, and its application in chicken breast. The minimum inhibitory concentration (MIC) of OEO against E. faecalis strains (ATCC 29212 and nine isolates) ranged from 0.25 to 0.50 μL/mL. OEO therapy reduced intracellular adenosine triphosphate (ATP) levels, caused cell membrane hyperpolarization, increased the intracellular reactive oxygen species (ROS), and elevated extracellular malondialdehyde (MDA) concentrations. Furthermore, OEO treatment diminished cell membrane integrity and caused morphological alterations in the cells. In biofilms on stainless-steel, OEO showed effective inactivation activity against E. faecalis. OEO reduced the number of viable cells, cell viability and exopolysaccharides in the biofilm, as well as destroying its structure. Application of OEO on chicken breast results in a considerable reduction in E. faecalis counts and pH values, in comparison to control samples. These findings suggest that OEO could be utilized as a natural antibacterial preservative and could effectively control E. faecalis in food manufacturing.

Antioxidant and Antibacterial Activity of Helichrysum italicum (Roth) G. Don. from Central Europe

Helichrysum italicum (Roth) G. Don. is one of the most important cosmetic and medicinal plants originating from the Mediterranean region of Europe. The aim of this study was to assess the chemical profile as well as antioxidant and antibacterial potential of the species cultivated in the temperate climate of Central Europe. The analyses were carried out using herbs and inflorescences. The content of essential oil ranged from 0.25 g × 100 g⁻¹ in the herb to 0.31 g × 100 g⁻¹ in the inflorescences. Neryl acetate, accompanied by α-pinene in the herb (10.42%), and nerol in inflorescences (15.73%) were the dominants here. Rutoside, as well as rosmarinic, chlorogenic, neochlorogenic, isochlorogenic b and cichoric acids, were detected in both raw materials using HPLC-DAD. Within this group, cichoric acid was the dominant (2647.90 mg × 100 g⁻¹ in the herb, 1381.06 mg × 100 g⁻¹ in the inflorescences). The herb appeared to be more abundant in phenolics in comparison with the inflorescences. When given antioxidant activity (determined using DPPH and ABTS assays), both methanolic extract and essential oil obtained from the herb indicated higher potential than those originating from the inflorescences (74.72, 61.38 and 63.81, 58.59% in the case of DPPH, respectively). In turn, regarding antimicrobial activity, the essential oil from inflorescences was distinguished by stronger bacteriostatic power than the herb essential oil. Gram-positive bacteria were more sensitive to both essential oils in comparison with Gram-negative ones, with S. aureus ATCC 25923 as the most susceptible (MIC 1; MBC 16 mg × mL⁻¹) among tested strains.

Antioxidant and Toxic Activity of Helichrysum arenarium (L.) Moench and Helichrysum italicum (Roth) G. Don Essential Oils and Extracts

Helichrysum arenarium (L.) Moench (sandy everlasting) is the only species from genus Helichrysum Mill that grows spontaneously in Lithuania. The chemical composition of the essential oils (EOs) from inflorescences and leaves of H. arenarium wild plants was analysed by GC-MS. Palmitic (≤23.8%), myristic (≤14.9%) and lauric (6.1%) acids, n-nonanal (10.4%), and trans-β-caryophyllene (≤6.5%) were the major constituents in the EOs. For comparison, the main components in EO from flowers (commercial herb material) of H.italicum were γ-curcumene (21.5%), β-selinene (13.6%), α-selinene (8.1%), β-eudesmol (8.3%), and α-pinene (6.5%). Composition of H. arenarium methanolic extracts was investigated by HPLC-DAD-TOF. The main compounds were the following: luteolin-7-O-glucoside, naringenin and its glucoside, apigenin, chlorogenic acid, arenol, and arzanol. Antioxidant activity of EOs and extracts was tested by DPPH^● and ABTS^●+ assays. Sandy everlasting extracts exhibited significantly higher radical scavenging activities (for leaves 11.18 to 19.13 and for inflorescences 1.96 to 6.13 mmol/L TROLOX equivalent) compared to those of all tested EOs (0.25 to 0.46 mmol/L TROLOX equivalent). Antioxidant activity, assayed electrochemically by cyclic and square wave voltammetry correlated with total polyphenolic content in extracts and radical scavenging properties of EOs and extracts. The toxic activity of EOs of both Helichrysum species was evaluated using a brine shrimp (Artemia salina) bioassay. H. italicum inflorescence EO was found to be toxic (LC₅₀ = 15.99 µg/mL) as well as that of H. arenarium (LC₅₀ ≤ 23.42 µg/mL) oils.

Linking the antimicrobial and anti-inflammatory effects of immortelle essential oil with its chemical composition - The interplay between the major and minor constituents

Immortelle (Helichrysum italicum, Asteraceae) essential oil has been widely used in alternative medicine to accelerate wound healing, as well as in cosmetic products to stimulate skin regeneration and to reduce the appearance of wrinkles. It is also considered a natural and safe culinary spice that could also be applied in the food industry as a preservative in the future. The therapeutic efficacy of this oil changes with the natural variability of the composition. Herein we tested and mutually compared the antimicrobial and anti-inflammatory activities of four commercial immortelle oils differing in the relative amounts of marker compounds, i.e. neryl esters, α-pinene, γ- and ar-curcumenes, and β-diketones. The anti-inflammatory effect of selected chromatographic fractions, enriched in the aforementioned constituents, was evaluated by studying toxicity toward rat peritoneal macrophages, their nitric oxide production, myeloperoxidase, and arginase activities. Subsequently, the compositional and activity data were subjected to a multivariate statistical treatment to reveal the possible correlation(s) between the percentage of essential-oil constituents and the observed activities. The obtained results imply that immortelle oil efficiency as an antimicrobial and/or anti-inflammatory agent is most plausibly a result of a synergistic action between its constituents, and/or, rather unexpectedly, the presence of some minor constituents.

Synthetic cajaninstilbene acid derivatives eradicate methicillin-resistant Staphylococcus aureus persisters and biofilms

The Staphylococcus aureus can switch to a transient genotype-invariant dormancy, known as a persister, to survive treatment with high doses of antibiotics. This transient persister is an important reason underlying its resistance. There is an urgent need to find new antibacterial agents capable of eradicating methicillin-resistant S. aureus (MRSA) persisters. In this study, 37 new derivatives of cajaninstilbene acid (CSA) were designed and synthesized, and their biological activity against MRSA persisters was evaluated. Most of the newly synthesized derivatives exhibit more potent antimicrobial properties against S. aureus and MRSA than CSA itself, and 23 of the 37 derivatives show a tendency to eradicate MRSA persisters. A representative compound (A6) was demonstrated to target bacterial cell membranes. It eradicated the adherent biofilm of MRSA in a concentration dependent manner, and showed a synergistic antibacterial effect with piperacilin. In a model mouse abscess caused by MRSA persisters, A6 effectively reduced the bacterial load in vivo. These results indicate that A6 is a potential candidate for treatment of MRSA persister infections.

Helichrysum araxinum Takht. ex Kirp. grown in Italy: volatiloma composition and in vitro antimicrobial activity

In the present work the composition of biogenic volatile organic compounds (BVOCs) and the essential oil (EO) of Helichrysum araxinum Takht. ex Kirp. aerial parts, together with the antimicrobial activity, were investigated. The results showed the prevalence of sesquiterpene hydrocarbons in both spontaneous emissions as well as in the EO. The main compounds of BVOCs were γ-curcumene (10.7%), γ-muurolene (9.2%), and β-selinene (8.5%). This latter constituent also showed a similar amount in the EO and represented the most abundant compounds together with α-selinene (8.0%). It is Interesting to note the same percentage of monoterpene hydrocarbons (MHs) in both the aroma profile and the EO (18.0%) with the same most abundant compounds: β-pinene (6.3% in BVOCs vs. 5.1% in EO, respectively) and limonene (4.5% in VOCs vs. 4.9% in EO, respectively). With regard to the antimycotic activity, the EO showed to be inactive against the tested strains, while a moderate antibacterial activity was shown against Staphylococcus isolates.

Action mode of cranberry anthocyanin on physiological and morphological properties of Staphylococcus aureus and its application in cooked meat

This study researched the action mode of cranberry anthocyanin (CA) against Staphylococcus aureus and the effect of CA on the counts of S. aureus and the quantity of cooked meat during storage. The antibacterial effect was assessed by minimum inhibitory concentration (MIC) and survival populations of S. aureus strains after CA treatments. The changes in intracellular adenosine 5'-triphosphate (ATP) concentration, cell membrane potential, content of bacterial protein and cell morphology were analyzed to reveal possible action mode. Application potentials of CA as antimicrobial agent were assessed during storage of cooked pork and beef. The result showed that the MIC of CA against S. aureus strains was 5 mg/mL. Approximately 8 log CFU/mL of S. aureus strains can be completely inhibited after treatment with 2.0 MIC of CA for 0.5 h. Treatments of CA resulted in lower intracellular ATP and soluble protein levels, damaged membrane structure and leakage of cytoplasmic. Application of CA on cooked pork and beef caused a significant decrease in S. aureus counts and pH values, and color-darkening compared with control samples. These findings demonstrated that CA played an effective antimicrobial against S. aureus and had a potential as natural preservative to inhibit the growth of food pathogens.

Antibacterial Activity of Olive Oil Polyphenol Extract Against Salmonella Typhimurium and Staphylococcus aureus: Possible Mechanisms

Polyphenols are a group of active ingredients in olive oil, and have been reported to exhibit antioxidant activity. Salmonella enterica subsp. enterica serovar Typhimurium (Salmonella Typhimurium) and Staphylococcus aureus are common foodborne pathogens causing serious infections and food poisoning in humans. This study was conducted to analyze the antibacterial activity of olive oil polyphenol extract (OOPE) against Salmonella Typhimurium and S. aureus, and reveal the possible antibacterial mechanism. The antibacterial activity was estimated using minimum inhibitory concentration (MIC) values and bacterial survival rates when treated with OOPE. The antibacterial mechanism was revealed through determinations of changes in intracellular ATP concentration and cell membrane potential, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and transmission electron microscopy analysis. The results showed the MICs of OOPE against Salmonella Typhimurium and S. aureus were 0.625 and 0.625-1.25 mg/mL, respectively. The growth of Salmonella Typhimurium and S. aureus (∼8 log CFU/mL) was completely inhibited after treatments with 0.625 mg/mL of OOPE for 3 h and 0.625-1.25 mg/mL for 5 h, respectively. When Salmonella Typhimurium and S. aureus were exposed to OOPE, the physiological functions associated with cell activity were destroyed, as manifested by reduction of intracellular ATP concentrations, cell membrane depolarization, lower bacterial protein content, and leakage of cytoplasm. These findings suggested a strong antibacterial effect of OOPE against Salmonella Typhimurium and S. aureus, and provided a possible strategy of controlling contamination by these two pathogens in food products.

Separation of phytochemicals from Helichrysum italicum: An analysis of different isolation techniques and biological activity of prepared extracts

Helichrysum italicum presents a valuable source of natural bioactive compounds. In this work, a literature review of terpenes, phenolic compounds, and other less common phytochemicals from H. italicum with regard to application of different separation methods is presented. Data including extraction/separation methods and experimental conditions applied, obtained yields, number of identified compounds, content of different compound groups, and analytical techniques applied are shown as corresponding tables. Numerous biological activities of both isolates and individual compounds are emphasized. In addition, the data reported are discussed, and the directions for further investigations are proposed.