Antibacterial Activities AgainstStaphylococcus aureusof Terpene Alcohols With Aliphatic Carbon Chains

Multidrug resistance of Botrytis cinerea associated with its adaptation to plant secondary metabolites

Fungicides are an effective way to control gray mold of grapes, but the pathogen Botrytis cinerea can develop resistance, overcoming the effectiveness of a fungicide that is repeatedly applied. More importantly, the emergence of multidrug resistance (MDR) in the field, where multiple fungicides with different modes of action simultaneously lose their efficacies, is a significant concern. MDR is associated with ATP-binding cassette (ABC) transporters of the pathogen, and certain plant secondary metabolites (PSMs) stimulate the upregulation of ABC transporters, we hypothesized that the pathogen's preadaptation to PSMs might contribute to MDR development. To test this in B. cinerea, ten PSMs, namely, resveratrol, reserpine, chalcone, flavanone, eugenol, farnesol, anethene, camptothecin, salicylic acid, and psoralen, were selected based on their association with ABC transporters involved in fungicide resistance. B. cinerea strain B05.10 was continuously transferred for 15 generations on potato dextrose agar amended with a PSM (PDAP), and sensitivities to PSMs and fungicides were examined on the 5th, 10th, and 15th generations. RNA was extracted from B. cinerea from the selected generations. After 15 generations of culture transfers, an up-regulation was observed in the expression of ABC transporter-encoding genes BcatrB, BcatrD, and BcatrK using quantitative polymerase chain reaction (qPCR). This upregulation was found to contribute to MDR of B. cinerea against two or more fungicides, among azoxystrobin, boscalid, fludioxonil, difenoconazole, prochloraz, and pyrimethanil. This finding was confirmed through genetic transformation. The decreased sensitivity of B. cinerea to fungicides was confirmed as a subsequent MDR phenotype after exposure to camptothecin, flavanone, and resveratrol. Besides, transcriptome analysis also revealed the upregulation of transcription factors related to ABC expression following resveratrol exposure. This suggests that PSMs contributed to inducing preadaptation of B. cinerea, leading to subsequent MDR.IMPORTANCEThe emergence of MDR in plant pathogens is a threat to plant disease management and leads to the use of excessive fungicides. Botrytis cinerea is of particular concern because its MDR has widely emerged in the field. Understanding its genesis is the first step for controlling MDR. In this study, the contribution of PSMs to MDR has been examined. Effective management of this pathogen in agroecosystems relies on a better understanding of how it copes with phytochemicals or fungicides.

Silicone-geranium essential oil blend for long-term antifouling coatings

This study explores the potential of geranium essential oil as a natural solution for combating marine biofouling, addressing the environmental concerns associated with commercial antifouling coatings. Compounds with bactericidal activities were identified by 13Carbon nuclear magnetic resonance (13C NMR). Thermogravimetric analysis (TGA) revealed minimal impact on film thermal stability, maintaining suitability for antifouling applications. The addition of essential oil induced changes in the morphology of the film and Fourier transform infrared spectroscopy (FTIR) analysis indicated that oil remained within the film. Optical microscopy showed an increase in coating porosity after immersion in a marine environment. A total of 18 bacterial colonies were isolated, with Psychrobacter adeliensis and Shewanella algidipiscicola being the predominant biofilm-forming species. The geranium essential oil-based coating demonstrated the ability to reduce the formation of Psychrobacter adeliensis biofilms and effectively inhibit macrofouling adhesion for a duration of 11 months.

Perspective of Secondary Metabolites in Respect of Multidrug Resistance (MDR): A Review

Aberrant and haphazard use of antibiotics has created the development of antimicrobial resistance which is a bizarre challenge for human civilization. This emerging crisis of antibiotic resistance for microbial pathogens is alarming all the nations posing a global threat to human health. It is difficult to treat bacterial infections as they develop resistance to all antimicrobial resistance. Currently used antibacterial agents inhibit a variety of essential metabolic pathways in bacteria, including macro-molecular synthesis (MMS) pathways (e.g. protein, DNA, RNA, cell wall) most often by targeting a specific enzyme or subcellular component e.g. DNA gyrase, RNA polymerase, ribosomes, transpeptidase. Despite the availability of diverse synthetic molecules, there are still many complications in managing progressive and severe antimicrobial resistance. Currently not even a single antimicrobial agent is available for which the microbes do not show resistance. Thus, the lack of efficient drug molecules for combating microbial resistance requires continuous research efforts to overcome the problem of multidrug-resistant bacteria. The phytochemicals from various plants have the potential to combat the microbial resistance produced by bacteria, fungi, protozoa and viruses without producing any side effects. This review is a concerted effort to identify some of the major active phytoconstituents from various medicinal plants which might have the potential to be used as an alternative and effective strategy to fight against microbial resistance and can promote research for the treatment of MDR.

Real-time in vivo monitoring of the antimicrobial action of combination therapies in the management of infected topical wounds

The increasing prevalence of non-healing infected wounds has become a serious concern in the clinical practice, being associated to population aging and to the rising prevalence of several chronic conditions such as diabetes. Herein, the evaluation of the bactericidal and antibiofilm effects of the natural antiseptic terpenes thymol and farnesol standing alone or in combination with the standard care antiseptic chlorhexidine was carried out both in vitro and in vivo. The in vitro combinatorial treatment of chlorhexidine associated with those terpenes against Staphylococcus aureus in its planktonic and sessile forms demonstrated a superior antibacterial activity than that of chlorhexidine alone. Real-time in vivo monitoring of infection progression and antimicrobial treatment outcomes were evaluated using the bioluminescent S. aureus strain Xen36. In vivo studies on infected wound splinting murine models corroborated the superior bactericidal effects of the combinatorial treatments here proposed. Moreover, the encapsulation of thymol in electrospun Eudragit® S100 (i.e., a synthetic anionic copolymer of methacrylic acid and ethyl acrylate)-based wound dressings was also carried out in order to design efficient antimicrobial wound dressings.

Phytochemicals as Antimicrobials: Prospecting Himalayan Medicinal Plants as Source of Alternate Medicine to Combat Antimicrobial Resistance

Among all available antimicrobials, antibiotics hold a prime position in the treatment of infectious diseases. However, the emergence of antimicrobial resistance (AMR) has posed a serious threat to the effectiveness of antibiotics, resulting in increased morbidity, mortality, and escalation in healthcare costs causing a global health crisis. The overuse and misuse of antibiotics in global healthcare setups have accelerated the development and spread of AMR, leading to the emergence of multidrug-resistant (MDR) pathogens, which further limits treatment options. This creates a critical need to explore alternative approaches to combat bacterial infections. Phytochemicals have gained attention as a potential source of alternative medicine to address the challenge of AMR. Phytochemicals are structurally and functionally diverse and have multitarget antimicrobial effects, disrupting essential cellular activities. Given the promising results of plant-based antimicrobials, coupled with the slow discovery of novel antibiotics, it has become highly imperative to explore the vast repository of phytocompounds to overcome the looming catastrophe of AMR. This review summarizes the emergence of AMR towards existing antibiotics and potent phytochemicals having antimicrobial activities, along with a comprehensive overview of 123 Himalayan medicinal plants reported to possess antimicrobial phytocompounds, thus compiling the existing information that will help researchers in the exploration of phytochemicals to combat AMR.

A novel water-soluble chitosan grafted with nerol: Synthesis, characterization and biological activity

In order to improve the antibacterial activity of chitosan and change its solubility, a novel water-soluble chitosan (CS)-nerol (N) derivative (CS-N) was prepared via Schiff base reaction and grafting reaction. FT-IR, NMR, XRD, TGA and SEM were used to characterize the structure and physicochemical properties, and in vitro antibacterial, antioxidant, and cellular assays were used to test for bioactivity and safety. The results revealed that the C6 hydroxyl group of CS was substituted with N, with a degree of substitution of 38 % for CS-N. Furthermore, compared to CS, CS-N demonstrated superior antibacterial activity against Escherichia coli and Staphylococcus aureus, as well as significant DPPH and ABTS free radical scavenging activity. Most importantly, CS-N did not harm HaCaT cells. In conclusion, this study provides a promising strategy for the design of chitosan derivatives with significant potential for application in pharmaceutical, food and cosmetic applications.

Harnessing the Role of Bacterial Plasma Membrane Modifications for the Development of Sustainable Membranotropic Phytotherapeutics

Membrane-targeted molecules such as cationic antimicrobial peptides (CAMPs) are amongst the most advanced group of antibiotics used against drug-resistant bacteria due to their conserved and accessible targets. However, multi-drug-resistant bacteria alter their plasma membrane (PM) lipids, such as lipopolysaccharides (LPS) and phospholipids (PLs), to evade membrane-targeted antibiotics. Investigations reveal that in addition to LPS, the varying composition and spatiotemporal organization of PLs in the bacterial PM are currently being explored as novel drug targets. Additionally, PM proteins such as Mla complex, MPRF, Lpts, lipid II flippase, PL synthases, and PL flippases that maintain PM integrity are the most sought-after targets for development of new-generation drugs. However, most of their structural details and mechanism of action remains elusive. Exploration of the role of bacterial membrane lipidome and proteome in addition to their organization is the key to developing novel membrane-targeted antibiotics. In addition, membranotropic phytochemicals and their synthetic derivatives have gained attractiveness as popular herbal alternatives against bacterial multi-drug resistance. This review provides the current understanding on the role of bacterial PM components on multidrug resistance and their targeting with membranotropic phytochemicals.

Synergy by Perturbing the Gram-Negative Outer Membrane: Opening the Door for Gram-Positive Specific Antibiotics

New approaches to target antibacterial agents toward Gram-negative bacteria are key, given the rise of antibiotic resistance. Since the discovery of polymyxin B nonapeptide as a potent Gram-negative outer membrane (OM)-permeabilizing synergist in the early 1980s, a vast amount of literature on such synergists has been published. This Review addresses a range of peptide-based and small organic compounds that disrupt the OM to elicit a synergistic effect with antibiotics that are otherwise inactive toward Gram-negative bacteria, with synergy defined as a fractional inhibitory concentration index (FICI) of <0.5. Another requirement for the inclusion of the synergists here covered is their potentiation of a specific set of clinically used antibiotics: erythromycin, rifampicin, novobiocin, or vancomycin. In addition, we have focused on those synergists with reported activity against Gram-negative members of the ESKAPE family of pathogens namely, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and/or Acinetobacter baumannii. In cases where the FICI values were not directly reported in the primary literature but could be calculated from the published data, we have done so, allowing for more direct comparison of potency with other synergists. We also address the hemolytic activity of the various OM-disrupting synergists reported in the literature, an effect that is often downplayed but is of key importance in assessing the selectivity of such compounds for Gram-negative bacteria.

Tackling Multiple-Drug-Resistant Bacteria With Conventional and Complex Phytochemicals

Emerging antibiotic resistance in bacteria endorses the failure of existing drugs with chronic illness, complicated treatment, and ever-increasing expenditures. Bacteria acquire the nature to adapt to starving conditions, abiotic stress, antibiotics, and our immune defense mechanism due to its swift evolution. The intense and inappropriate use of antibiotics has led to the development of multidrug-resistant (MDR) strains of bacteria. Phytochemicals can be used as an alternative for complementing antibiotics due to their variation in metabolic, genetic, and physiological fronts as well as the rapid evolution of resistant microbes and lack of tactile management. Several phytochemicals from diverse groups, including alkaloids, phenols, coumarins, and terpenes, have effectively proved their inhibitory potential against MDR pathogens through their counter-action towards bacterial membrane proteins, efflux pumps, biofilms, and bacterial cell-to-cell communications, which are important factors in promoting the emergence of drug resistance. Plant extracts consist of a complex assortment of phytochemical elements, against which the development of bacterial resistance is quite deliberate. This review emphasizes the antibiotic resistance mechanisms of bacteria, the reversal mechanism of antibiotic resistance by phytochemicals, the bioactive potential of phytochemicals against MDR, and the scientific evidence on molecular, biochemical, and clinical aspects to treat bacterial pathogenesis in humans. Moreover, clinical efficacy, trial, safety, toxicity, and affordability investigations, current status and developments, related demands, and future prospects are also highlighted.

In vitro Effect of Geranylgeraniol (GGOH) on Bisphosphonate-Induced Cytotoxicity of Oral Mucosa Cells

Medication-related osteonecrosis of the jaw (MRONJ) is an often-severe complication found in patients receiving bisphosphonates in the management of Paget's, osteoporosis and metastatic bone cancer. Mucosal breakdown with bone exposure is a primary clinical presentation of MRONJ linked to the inhibitory effect of nitrogen-containing bisphosphonates (N-BP) on the mevalonate pathway. Geranylgeraniol (GGOH) has demonstrated a rescue effect on N-BP-treated osteoclasts but the biological effects on oral soft tissues and cells remain unclear. This study aimed to determine whether GGOH could prevent bisphosphonate induced toxicity to oral mucosa cells in vitro. Primary oral fibroblasts and keratinocytes were exposed to different GGOH concentrations or GGOH in combination with two nitrogen-containing bisphosphonates, zoledronic acid (ZA) or pamidronic acid (PA), for 72 h. The metabolic activity of each cell type was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. GGOH without bisphosphonates significantly reduced the metabolic activity of oral mucosa cells. Fibroblasts treated with GGOH and ZA in combination showed a slight increase in metabolic status compared to fibroblasts treated with ZA alone, however this positive effect was not observed in keratinocytes. In the presence of PA, GGOH was unable to increase the metabolic activity of either cell type. These findings demonstrate that GGOH is toxic to oral mucosa cells and that GGOH was not able to prevent bisphosphonate induced toxicity. These data show that GGOH does not have therapeutic potential for bisphosphonate-induced soft tissue toxicity in MRONJ and the use of GGOH as an MRONJ treatment should be strongly reconsidered.

Transcriptomic analysis of interactions between Lymantria dispar larvae and carvacrol

Due to its biological activity, carvacrol (CAR) is widely used in medicine, agriculture, and forestry. Our previous studies showed that in Lymantria dispar larvae, CAR treatment can induce the production of antifeedants and lead to growth inhibition and death of larvae. However, the effect CAR exerts on RNA levels in L. dispar larvae remains unclear. In this study, the Illumina HiSeq4000 sequencing platform was used to sequence the total RNA of L. dispar larvae. A total of six cDNA libraries (three treatments and three controls) were established and 39,807 genes were generated. Compared with the control group, 296 differentially expressed genes (DEGs) (142 up-regulated and 154 down-regulated) were identified after CAR treatment. GO and KEGG enrichment analyses showed that these DEGs mainly clustered in the metabolism of xenobiotics, carbohydrates, and lipids. Furthermore, 12 DEGs were found to be involved in detoxification, including six cytochrome P450s, two esterases, one glutathione peroxidase, one UDP-glycosyltransferase gene, and two genes encoding heat shock proteins. The expression levels of detoxification genes changed under CAR treatment (especially P450s), which further yielded candidate genes for explorations of the insecticidal mechanism of CAR. The reliability of transcriptome data was verified by qRT-PCR. The enzyme activities of CYP450 and acid phosphatase significantly increased (by 38.52 U/mg·prot and 0.12 μmol/min·mg, respectively) 72 h after CAR treatment. However, the activity of alkaline phosphatase did not change significantly. These changes in enzyme activity corroborated the reliability of the transcriptome data at the protein level. The results of GO enrichment analysis of DEGs indicated that CAR influenced the oxidation-reduction process in L. dispar larvae. Furthermore, CAR can cause oxidative stress in L. dispar larvae, identified through the determination of peroxidase and polyphenol oxidase activities, total antioxidant capacity, and hydrogen peroxide content. This study provides useful insight into the insecticidal mechanism of CAR.

Antibiotic resistance modifying ability of phytoextracts in anthrax biological agent Bacillus anthracis and emerging superbugs: a review of synergistic mechanisms

Background and objectives

The chemotherapeutic management of infections has become challenging due to the global emergence of antibiotic resistant pathogenic bacteria. The recent expansion of studies on plant-derived natural products has lead to the discovery of a plethora of phytochemicals with the potential to combat bacterial drug resistance via various mechanisms of action. This review paper summarizes the primary antibiotic resistance mechanisms of bacteria and also discusses the antibiotic-potentiating ability of phytoextracts and various classes of isolated phytochemicals in reversing antibiotic resistance in anthrax agent Bacillus anthracis and emerging superbug bacteria.

Methods

Growth inhibitory indices and fractional inhibitory concentration index were applied to evaluate the in vitro synergistic activity of phytoextract-antibiotic combinations in general.

Findings

A number of studies have indicated that plant-derived natural compounds are capable of significantly reducing the minimum inhibitory concentration of standard antibiotics by altering drug-resistance mechanisms of B. anthracis and other superbug infection causing bacteria. Phytochemical compounds allicin, oleanolic acid, epigallocatechin gallate and curcumin and Jatropha curcas extracts were exceptional synergistic potentiators of various standard antibiotics.

Conclusion

Considering these facts, phytochemicals represents a valuable and novel source of bioactive compounds with potent antibiotic synergism to modulate bacterial drug-resistance.

Towards Advances in Medicinal Plant Antimicrobial Activity: A Review Study on Challenges and Future Perspectives

The increasing incidence of drug- resistant pathogens raises an urgent need to identify and isolate new bioactive compounds from medicinal plants using standardized modern analytical procedures. Medicinal plant-derived compounds could provide novel straightforward approaches against pathogenic bacteria. This review explores the antimicrobial activity of plant-derived components, their possible mechanisms of action, as well as their chemical potential. The focus is put on the current challenges and future perspectives surrounding medicinal plants antimicrobial activity. There are some inherent challenges regarding medicinal plant extracts and their antimicrobial efficacy. Appropriate and optimized extraction methodology plant species dependent leads to upgraded and selective extracted compounds. Antimicrobial susceptibility tests for the determination of the antimicrobial activity of plant extracts may show variations in obtained results. Moreover, there are several difficulties and problems that need to be overcome for the development of new antimicrobials from plant extracts, while efforts have been made to enhance the antimicrobial activity of chemical compounds. Research on the mechanisms of action, interplay with other substances, and the pharmacokinetic and/or pharmacodynamic profile of the medicinal plant extracts should be given high priority to characterize them as potential antimicrobial agents.

Exploring Phytochemicals for Combating Antibiotic Resistance in Microbial Pathogens

Antibiotic resistance or microbial drug resistance is emerging as a serious threat to human healthcare globally, and the multidrug-resistant (MDR) strains are imposing major hurdles to the progression of drug discovery programs. Newer antibiotic-resistance mechanisms in microbes contribute to the inefficacy of the existing drugs along with the prolonged illness and escalating expenditures. The injudicious usage of the conventional and commonly available antibiotics in human health, hygiene, veterinary and agricultural practices is proving to be a major driver for evolution, persistence and spread of antibiotic-resistance at a frightening rate. The drying pipeline of new and potent antibiotics is adding to the severity. Therefore, novel and effective new drugs and innovative therapies to treat MDR infections are urgently needed. Apart from the different natural and synthetic drugs being tested, plant secondary metabolites or phytochemicals are proving efficient in combating the drug-resistant strains. Various phytochemicals from classes including alkaloids, phenols, coumarins, terpenes have been successfully demonstrated their inhibitory potential against the drug-resistant pathogens. Several phytochemicals have proved effective against the molecular determinants responsible for attaining the drug resistance in pathogens like membrane proteins, biofilms, efflux pumps and bacterial cell communications. However, translational success rate needs to be improved, but the trends are encouraging. This review highlights current knowledge and developments associated challenges and future prospects for the successful application of phytochemicals in combating antibiotic resistance and the resistant microbial pathogens.

Evaluation of the antioxidant, antibacterial, and antibiofilm activity of the sesquiterpene nerolidol

The aim of this study was to evaluate the antioxidant, antibacterial, and antibiofilm activities of nerolidol. The antioxidant activity of nerolidol was determined using the total antioxidant activity method. Antibacterial activity was performed using the microdilution method to determine the minimum inhibitory concentration (MIC) against seven standard strains of the ATCC and four bacterial clinical isolates with a resistance profile, following the Clinical and Laboratory Standards Institute (CLSI). The antibiofilm activity of nerolidol was performed using the crystal violet method. The results of the antioxidant test revealed a total antioxidant activity of 93.94%. Nerolidol inhibited the growth of Staphylococcus aureus (MIC = 1 mg/mL), Streptococcus mutans (MIC = 4 mg/mL), Pseudomonas aeruginosa (MIC = 0.5 mg/mL), and Klebsiella pneumoniae (MIC = 0.5 mg/mL). For clinical isolates, nerolidol showed an inhibitory potential against multidrug-resistant P. aeruginosa, K. pneumoniae carbapenemase (MIC = 0.5 mg/mL), methicillin-susceptible S. aureus (MIC = 2 mg/mL), and methicillin-resistant S. aureus (MIC = 2 mg/mL). Nerolidol showed similar antibacterial activity against ATCC strains and hospital clinical isolates with resistance profile, suggesting that even though these strains are resistant to antibiotics, they are still sensitive to nerolidol. Nerolidol exerted a dose-dependent effect on the inhibition of biofilm formation, even at subinhibitory concentrations. Nerolidol inhibited bacterial biofilms of ATCC strains at a rate ranging from 51 to 98%, at concentrations ranging from 0.5 to 4 mg/mL. For clinical bacterial isolates, biofilm inhibition ranged from 6 to 60%. Therefore, the present study showed the antioxidant, antibacterial, and antibiofilm properties of nerolidol.

Plant Secondary Metabolites in the Battle of Drugs and Drug-Resistant Bacteria: New Heroes or Worse Clones of Antibiotics?

Infectious diseases that are caused by bacteria are an important cause of mortality and morbidity in all regions of the world. Bacterial drug resistance has grown in the last decades, but the rate of discovery of new antibiotics has steadily decreased. Therefore, the search for new effective antibacterial agents has become a top priority. The plant kingdom seems to be a deep well for searching for novel antimicrobial agents. This is due to the many attractive features of plants: they are readily available and cheap, extracts or compounds from plant sources often demonstrate high-level activity against pathogens, and they rarely have severe side effects. The huge variety of plant-derived compounds provides very diverse chemical structures that may supply both the novel mechanisms of antimicrobial action and provide us with new targets within the bacterial cell. In addition, the rapid development of modern biotechnologies opens up the way for obtaining bioactive compounds in environmentally friendly and low-toxic conditions. In this short review, we ask the question: do antibacterial agents derived from plants have a chance to become a panacea against infectious diseases in the "post-antibiotics era".

Review on plant antimicrobials: a mechanistic viewpoint

Microbial resistance to classical antibiotics and its rapid progression have raised serious concern in the treatment of infectious diseases. Recently, many studies have been directed towards finding promising solutions to overcome these problems. Phytochemicals have exerted potential antibacterial activities against sensitive and resistant pathogens via different mechanisms of action. In this review, we have summarized the main antibiotic resistance mechanisms of bacteria and also discussed how phytochemicals belonging to different chemical classes could reverse the antibiotic resistance. Next to containing direct antimicrobial activities, some of them have exerted in vitro synergistic effects when being combined with conventional antibiotics. Considering these facts, it could be stated that phytochemicals represent a valuable source of bioactive compounds with potent antimicrobial activities.

Farnesol-Induced Disruption of the Staphylococcus aureus Cytoplasmic Membrane

Farnesol, a sesquiterpene alcohol with an aliphatic carbon chain, inhibited the growth of Staphylococcus aureus and induced the leakage of potassium ions. We investigated the action of farnesol on the cytoplasmic membrane of S. aureus. No ion channels that would account for the loss of potassium ions were detected. Electron paramagnetic resonance measurements suggested that farnesol proceeds into the cytoplasmic membrane of S. aureus cells, where it induces the disordering and eventual disruption of the cytoplasmic membrane. This was supported by the result that the effects of farnesol decreased by the addition of carotenoid which was the stabilizing reagent for the lipid bilayer.

Nerolidol: A Sesquiterpene Alcohol with Multi-Faceted Pharmacological and Biological Activities

Nerolidol (3,7,11-trimethyl-1,6,10-dodecatrien-3-ol) is a naturally occurring sesquiterpene alcohol that is present in various plants with a floral odor. It is synthesized as an intermediate in the production of (3E)-4,8-dimethy-1,3,7-nonatriene (DMNT), a herbivore-induced volatile that protects plants from herbivore damage. Chemically, nerolidol exists in two geometric isomers, a trans and a cis form. The usage of nerolidol is widespread across different industries. It has been widely used in cosmetics (e.g., shampoos and perfumes) and in non-cosmetic products (e.g., detergents and cleansers). In fact, U.S. Food and Drug Administration (FDA) has also permitted the use of nerolidol as a food flavoring agent. The fact that nerolidol is a common ingredient in many products has attracted researchers to explore more medicinal properties of nerolidol that may exert beneficial effect on human health. Therefore, the aim of this review is to compile and consolidate the data on the various pharmacological and biological activities displayed by nerolidol. Furthermore, this review also includes pharmacokinetic and toxicological studies of nerolidol. In summary, the various pharmacological and biological activities demonstrated in this review highlight the prospects of nerolidol as a promising chemical or drug candidate in the field of agriculture and medicine.

Himalayan Aromatic Medicinal Plants: A Review of their Ethnopharmacology, Volatile Phytochemistry, and Biological Activities

Aromatic plants have played key roles in the lives of tribal peoples living in the Himalaya by providing products for both food and medicine. This review presents a summary of aromatic medicinal plants from the Indian Himalaya, Nepal, and Bhutan, focusing on plant species for which volatile compositions have been described. The review summarizes 116 aromatic plant species distributed over 26 families.

Volatile oils: Potential agents for the treatment of respiratory infections

Due to presence of secondary bioactive metabolites, natural compounds are considered a major source of new active molecules that can be developed as new drugs. Infectious diseases, and mainly the common respiratory infections, are major challenges to the current chemotherapy systems and, therefore, there is a requirement to find new compounds with therapeutic potential. The volatile natural compounds and essential oils are the main treasure agents in the natural compounds with antibiotic potential. The present chapter reviews natural traditional remedies used in the treatment of respiratory infections with the emphasis on antibacterial, antiviral, and antiinflammation activities of the volatile natural compounds (essential oils, etc.), and provides a brief view in some of structural activity relationships between antibacterial potencies and chemical structures of the essential oil’s constituents.

Effect of farnesol on mevalonate pathway of Staphylococcus aureus

To investigate the mechanism of action by which farnesol functions as an antibacterial agent and inhibits Staphylococcus aureus growth, the growth rates of S. aureus cultured in farnesol versus S. aureus cultured in farnesol and supplemented with 3-hydroxy-3-methylglutaryl (HMG)-CoA or mevalonate were compared. The investigation was designed to observe whether farnesol affected on the mevalonate pathway by using the intermediate metabolites of the pathway. The resulting growth curves demonstrated that mevalonate reduced the antibacterial activity of farnesol, but HMG-CoA did not inhibit farnesol. These results suggest that farnesol affects the mevalonate pathway. Moreover, farnesol inhibited HMG-CoA reductase activity in an in vitro enzymatic assay.