Antimicrobial activity of essential oils and other plant extracts

The antimicrobial activity of plant oils and extracts has been recognized for many years. However, few investigations have compared large numbers of oils and extracts using methods that are directly comparable. In the present study, 52 plant oils and extracts were investigated for activity against Acinetobacter baumanii, Aeromonas veronii biogroup sobria, Candida albicans, Enterococcus faecalis, Escherichia col, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enterica subsp. enterica serotype typhimurium, Serratia marcescens and Staphylococcus aureus, using an agar dilution method. Lemongrass, oregano and bay inhibited all organisms at concentrations of < or = 2.0% (v/v). Six oils did not inhibit any organisms at the highest concentration, which was 2.0% (v/v) oil for apricot kernel, evening primrose, macadamia, pumpkin, sage and sweet almond. Variable activity was recorded for the remaining oils. Twenty of the plant oils and extracts were investigated, using a broth microdilution method, for activity against C. albicans, Staph. aureus and E. coli. The lowest minimum inhibitory concentrations were 0.03% (v/v) thyme oil against C. albicans and E. coli and 0.008% (v/v) vetiver oil against Staph. aureus. These results support the notion that plant essential oils and extracts may have a role as pharmaceuticals and preservatives.     

The effects of essential oils and their major compounds on fish bacterial pathogens – a review

The increased resistance of fish pathogens to conventional treatments has lead researchers to investigate the antibacterial properties of natural resources, such as essential oils (EOs) of plants, in an effort to find products that are less harmful to the environment. The objective of this review is to provide an overview of the studies, in vivo and in vitro, that addressed the use of EOs and their major compounds as antimicrobial agents in fish, to identify the best EOs and compounds to investigate considering feasibility of application and suggest possible future studies. To date, studies suggest that the use of EOs in the prevention and/or treatment of infectious diseases in fish may be a promising strategy to reduce the use of conventional antibiotics in aquaculture, since several EOs effectively reduce or avoid the effects of bacterial infections in fish. The use of EOs through nanotechnology delivery systems, especially in dietary supplementation experiments, is promising. This form of application of the EOs allows a potentiation and targeting of the desired effect of the EOs and also allows the protection of EOs active constituents against enzymatic hydrolysis, deserving further study.     

Vanadium compounds as antiparasitic agents: An approach to their mechanisms of action

BackgroundParasitic infections are a public health problem since they have high morbidity and mortality worldwide. In parasitosis such as malaria, leishmaniasis and trypanosomiasis it is necessary to develop new compounds for their treatment since an increase in drug resistance and toxic effects have been observed. Therefore, the use of different compounds that couple vanadium in their structure and that have a broad spectrum against different parasites have been proposed experimentally.ObjectiveReport the mechanisms of action exerted by vanadium in different parasites.ConclusionIn this review, some of the targets that vanadium compounds have were identified and it was observed that they have a broad spectrum against different parasites, which represents an advance to continue investigating therapeutic options.     

Antimutagenic compounds and their possible mechanisms of action

Mutagenicity refers to the induction of permanent changes in the DNA sequence of an organism, which may result in a heritable change in the characteristics of living systems. Antimutagenic agents are able to counteract the effects of mutagens. This group of agents includes both natural and synthetic compounds. Based on their mechanism of action among antimutagens, several classes of compounds may be distinguished. These are compounds with antioxidant activity; compounds that inhibit the activation of mutagens; blocking agents; as well as compounds characterized with several modes of action. It was reported previously that several antitumor compounds act through the antimutagenic mechanism. Hence, searching for antimutagenic compounds represents a rapidly expanding field of cancer research. It may be observed that, in recent years, many publications were focused on the screening of both natural and synthetic compounds for their beneficial muta/antimutagenicity profile. Thus, the present review attempts to give a brief outline on substances presenting antimutagenic potency and their possible mechanism of action. Additionally, in the present paper, a screening strategy for mutagenicity testing was presented and the characteristics of the most widely used antimutagenicity assays were described.     

Antibacterial action mechanisms and mode of trypsin inhibitors: a systematic review

This systematic review (SR) aimed to gather studies describing the antibacterial action mechanisms and mode of trypsin inhibitors. The review protocol was registered (PROSPERO: CRD42020189069). Original articles resulting from studies in animal models, in bacterial culture, and using cells that describe antibacterial action of trypsin inhibitor-type peptides or proteins were selected in PubMed, Science Direct, Scopus, Web of Science, BVS, and EMBASE. The methodological quality assessment was performed using the PRISMA and OHAT tool. 2382 articles were retrieved, 17 of which were eligible. Four studies demonstrated the action mechanism directly on the bacterial membrane, and the fifth study on endogenous proteases extracted from the bacteria themselves. The antibacterial action mode was presented in the other studies, which can generate bacteriostatic or bactericidal effects without describing the mechanisms. This study generated information to enable new preclinical or clinical studies with molecules contributing to public health.     

In vitro inhibition of Candida albicans growth by plant extracts and essential oils

The opportunistic Candida albicans yeast strain ATCC 10261 grows at 37 °C and gives germ tubes after 3 h on corn meal agar and blood plasma. It produces chlamydospores and assimilates sucrose, dextrose, galactose, maltose, trehalose and xylose among the tested carbon sources. Other growth characters were also investigated. The agar diffusion cut plug technique revealed that 200 l of Foeniculum vulgare Miller (fennel), Mentha piperita L. (peppermint) and Citrus limon (lemon) essential oils showed inhibitory actions. Fumigation test of the three essential oils had complete inhibition on the growth. The essential oil of Eucalyptus occidentalis End1 (eucalyptus, eucalypt) had no influence on C. albicans growth by the two tests. Meanwhile, methanol extracts of both leaves and male cones of the conifer Thuja orientalis (eastern thuya) had an inhibitory influence on the growth by two tests (cut plug and filter paper disc assay). In comparative tests the antibiotics mycostatin and dermatin had an inhibitory activity on C. albicans at the concentrations of 50–80 g per hole. Crude methanol extract of leaves of eastern thuya (10–80 g/ml) reduced C. albicans growth and intercellular protein nitrogen on liquid media.     

Antibacterial activity of selected plant essential oils against Escherichia coli O157:H7

AIMS: To quantify the antibacterial properties of five essential oils (EO) on a non-toxigenic strain of Escherichia coli O157:H7 in the presence and absence of a stabilizer and an emulsifier and at three different temperatures. METHODS AND RESULTS: Five EOs known to exhibit antibacterial properties were screened by disc diffusion assay and the most active were selected for further study in microdilution colorimetric assays. Oregano (Origanum vulgare) and thyme (Thymus vulgaris; light and red varieties) EO had the strongest bacteriostatic and bactericidal properties, followed by bay (Pimenta racemosa) and clove bud (Eugenia caryophyllata synonym: Syzygium aromaticum) EO. Oregano oil was colicidal at 625 microl l(-1) at 10, 20 and 37 degrees C. The addition of 0.05% (w/v) agar as stabilizer reinforced the antibacterial properties, particularly at 10 degrees C, whereas 0.25% (w/v) lecithin reduced antibacterial activity. Scanning electron micrographs showed extensive morphological changes to treated cells. CONCLUSIONS: Oregano and thyme EO possess significant in vitro colicidal and colistatic properties, which are exhibited in a broad temperature range and substantially improved by the addition of agar as stabilizer. Bay and clove bud EO are less active. Lecithin diminished antibacterial properties. The bactericidal concentration of oregano EO irreversibly damaged E. coli O157:H7 cells within 1 min. SIGNIFICANCE AND IMPACT OF THE STUDY: Oregano and light thyme EO, particularly when enhanced by agar stabilizer, may be effective in reducing the number or preventing the growth of E. coli O157:H7 in foods.     

Antibiofilm activity of selected plant essential oils and their major components

The aim of the study was to examine the antibiofilm activity of selected essential oils (EO): Lavandula angustifblia (LEO), Melaleuca alternifolia (TTO), Melissa officinalis (MEO) and some of their major constituents: linalool, linalyl acetate, alpha-terpineol, terpinen-4-ol. Biofilms were formed by Staphylococcus aureus ATCC 29213 and Escherichia coli NCTC 8196 on the surface of medical biomaterials (urinary catheter, infusion tube and surgical mesh). TTC reduction assay was used for the evaluation of mature biofilm eradication from these surfaces. Moreover, time-dependent eradication ofbiofilms preformed in polystyrene 96-well culture microplates was examined and expressed as minimal biofilm eradication concentration (evaluated by MTT reduction assay). TTO, alpha-terpineol and terpinen-4-ol as well as MEO, showed stronger anti-biofilm activity than LEO and linalool or linalyl acetate. Among the biomaterials tested, surgical mesh was the surface most prone to persistent colonization since biofilms formed on it, both by S. aureus and E. coli, were difficult to destroy. The killing rate studies of S. aureus biofilm treated with TTO, LEO, MEO and some of their constituents revealed that partial (50%) destruction of 24-h-old biofilms (MBEC50) was achieved by the concentration 4-8 x MIC after 1 h, whereas 2-4 x MIC was enough to obtain 90% reduction in biomass metabolic activity (MBEC90) after just 4 h of treatment. A similar dose-dependent effect was observed for E. coli biofilm which, however, was more susceptible to the action of phytochemicals than the biofilms of S. aureus. It is noteworthy that an evident decrease in biofilm cells metabolic activity does not always lead to their total destruction and eradication.     

Repellent efficacy of essential oils and plant extracts against Tribolium castaneum and Plodia interpunctella

This study was conducted to investigate the repellent efficacy of essential oils (Origanum vulgare, Pimpinella anisum, and Tanacetum cinerariifolium) and four plant extracts (Agastache rugosa, Capsicum annuum, Citrus reticulata, and Ginkgo biloba) against Tribolium castaneum (adults and larvae) and Plodia interpunctella (larvae). Gas chromatography/mass spectrometry analysis revealed the presence of carvacrol, anethole, and jasmolin I as the predominant constituent in O. vulgare, P. anisum, and T. cinerariifolium, respectively. Furthermore, ethyl hexopyranoside, 9,12‐octadecadienoic acid, cyclopentanol, and 2‐cresol were identified in A. rugosa, C. annuum, C. reticulata, and G. biloba, respectively. The repellent efficacy of each essential oil, plant extract, and the combination of oils was evaluated using a specially designed cylinder trap for 120 h. Among the three oils, O. vulgare and T. cinerariifolium had greatest repellent efficacy against P. interpunctella larvae. T. cinerariifolium exhibited effective repellence against the adults and larvae of T. castaneum. Therefore, O. vulgare (O) and T. cinerariifolium (T) were selected for further investigation of combined effects. Two essential oils were mixed in three different ratios of OT1 (1:3), OT2 (1:1), and OT3 (3:1). The repellent efficacies of OT1 and OT2 against the adults of T. castaneum were significantly greater than that of OT3. OT1 was effective against the larvae of T. castaneum, whereas OT2 was effective against the larvae of P. interpunctella. OT1 enhanced the repellent efficacy by approximately five times against larvae of T. castaneum, compared with that of T. cinerariifolium. Overall, OT1 was selected as the best repellent substance against all the tested insects.     

Anabolic steroids: a review of their effects on the muscles, of their possible mechanisms of action and of their use in athletics.

Anabolic steroids are synthetic molecules developed in the hope of obtaining a complete separation of the androgenic and myotrophic (anabolic) actions of testosterone. Such a goal has never been fully achieved. However, some synthetic steroids present a partial dissociation between these two activities. Since a single hormonal receptor apparently mediates the androgenic as well as the anabolic actions of testosterone, differences in patterns of androgen metabolization in the muscles and the sex accessory organs have been proposed as a possible cause of this phenomenon. Undoubtedly, androgens are able to exert a trophic effect on skeletal and cardiac muscle fibres in subjects with low circulating levels of testosterone such as prepubertal or hypogonadal males and females; however, the widespread use of anabolic steroids in male athletes to increase their physical performances poses the question of whether these compounds are active in the presence of normal circulating levels of testosterone. Most experimental animal studies indicate that anabolic steroids are ineffective in this situation. Since the results of the experiments performed in humans are largely contradictory, it is still not clear whether anabolic steroids are able to improve athletic performances. These and other relevant issues are reviewed.     

Toxicity of plant essential oils and their components against Lycoriella ingenua (Diptera: Sciaridae)

Plant essential oils from 20 plant species were tested for their insecticidal activity against larvae of Lycoriella ingenua (Dufour) (Diptera: Sciaridae) by using a fumigation bioassay. Good insecticidal activity (>90%) against larvae of L. ingenua was achieved with essential oils of caraway seed Carum carvi (L.)], lemongrass [Cymbopogon citratus (D.C.) Stapf.], mandarine (Citrus reticulate Blanco), nutmeg (Myristica fragrans Houtt), cade (Juniperus oxycedrus L.), spearmint (Mentha spicata L.), cumin (Cuminum cyminum L.), and thyme red [Thymus vulgaris (L.)] oils at 30 X 10-3 mg/1 air. Among them, caraway seed, spearmint, cumin, and thyme red essential oils were highly effective against L. ingenua at 20 x 10(-3) mg/ml air. Analysis by gas chromatography-mass spectrometry led to identification of 4, 9, 8, and 17 compounds from caraway seed, spearmint, cumin, and thyme red oils, respectively. These compounds were tested individually for their insecticidal activities against larvae of L. ingenua, and compared with the toxicity of dichlorvos. Carvacrol, thymol, linalool, cuminaldehyde, p-cymen, terpinen-4-ol, and carvone was effective at 10 x 10(-3) mg/l. The insecticidal activity of dichlorvos was 60% at 10 x 10(-3) mg/ml. Effects of four selected plant essential oils on growth of oyster mushroom, Pleurotus ostreatus, also were investigated.     

Nematicidal activity of essential oils: a review

Plant parasitic nematodes are the most destructive group of plant pathogens worldwide and their control is extremely challenging. Plant Essential oils (EOs) and their constituents have a great potential in nematode control since they can be developed for use as nematicides themselves or can serve as model compounds for the development of derivatives with enhanced activity. This study reviews the plant EOs evaluated as potential nematicides and their toxic effects against pinewood nematode (Bursaphelenchus xylophilus) and root-knot nematodes (Meloidogyne spp.). Additionally, the nematicidal activity to M. javanica of several EOs from Spanish aromatic plants and their components is described.     

Endothelin: A review of its effects and possible mechanisms of action

The recently identified endothelium-derived peptide, endothelin, is a potent vasoconstrictor, but also binds specifically to many types of smooth muscle and to nerve tissue. Endothelin has been detected in plasma and may have physiological or pathological functions. Like other agonists, endothelin increases the turnover of phosphatidyl inositol and liberates intracellular stocks of Ca²⁺. It also increases plasmalemmal Ca²⁺ permeability, an effect that is antagonized by calcium entry blockers in some tissues. However, the characteristics of this antagonism are not always typical of that seen when other types of agonists are employed. It seems that in at least some cell types endothelin might activate specific L-type Ca²⁺ channels indirectly, perhaps secondarily to the activation of another type of cation channel. The endothelin originally described is one of a family of peptides that are closely related to the sarafotoxins. The comparative pharmacology of these peptides and of some analogues of the originally described endothelin have revealed some surprising differences and may indicate the existence of different endothelin receptors.Special issue dedicated to Dr. Sidney Udenfriend.     

Telomeres and telomerase: their mechanisms of action and the effects of altering their functions

The molecular features of telomeres and telomerase are conserved among most eukaryotes. How telomerase and telomeres function and how they interact to promote the chromosome-stabilizing properties of telomeres are discussed here.     

Antibacterial effect of essential oils and interaction with food components

The antibacterial effect of essential oils (EOs) derived from Citrus lemon, Juniperus communis, Origanum majorana, and Salvia sclarea, was investigated either alone or in combination, on 2 food related bacteria (Bacillus cereus and Escherichia coli). The influence of food ingredients — hydrolyzed proteins originating from animal and plant (meat extract and soy peptone) and sucrose — on the antibacterial effect of EOs was also tested. The most effective antibacterial activities were obtained with marjoram and clary sage oil, alone and in combination. High concentration of meat extract protected the bacteria from the growth inhibiting effect of marjoram oil, while soy peptone had no such effect. Sucrose intensified the lag phase lengthening by marjoram oil in a dose-independent manner.     

Efficacy of some medicinal plant extracts and essential oils against Colorado potato beetle,Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae)

The Colorado potato beetle (CPB), Leptinotarsa decemlineata Say is one of the most important defoliator pests of potato in the world and it often causes extremely large potato yield losses. Potatoes are the preferred hosts for the pest, but it may feed and reproduce on a number of other plants in the Solanaceae family. Public concern related to pesticides and their residues in and on the foods had prompted a rise of consumer interest in organically produced foods. There have been growing efforts to detect and introduce suitable plant compounds that they have insecticidal properties. However, discovering of plant extracts for possible use in control of this pest requires more studying about plant extracts and compounds. Since resistance of CPB to common chemical insecticides is well documented and potato is one of the most prominent nutritious food products for many people in many countries, we examined the effect of essential oils (EOs) of European pennyroyal, lavander, mint, oregano and savory and methanolic extracts of fumitory, licorice and oregano on the pest. These plants were selected because they have medicinal properties and they are safe to human and environment. Adult CPBs were exposed to mentioned plant extracts and essential oils. LC₅₀ values for EOs of lavander and European pennyroyal were 4154 and 3561 ppm, respectively. The results demonstrated that essential oil of European pennyroyal (Mentha longifolia) would be suitable compound to control the pest, but essential oil of mint (Mentha spicata) was not effective against the pest. Also it is notable that at all treatments, the amount of adult feeding was very low.     

Antibacterial free fatty acids: activities, mechanisms of action and biotechnological potential

Amongst the diverse and potent biological activities of free fatty acids (FFAs) is the ability to kill or inhibit the growth of bacteria. The antibacterial properties of FFAs are used by many organisms to defend against parasitic or pathogenic bacteria. Whilst their antibacterial mode of action is still poorly understood, the prime target of FFA action is the cell membrane, where FFAs disrupt the electron transport chain and oxidative phosphorylation. Besides interfering with cellular energy production, FFA action may also result from the inhibition of enzyme activity, impairment of nutrient uptake, generation of peroxidation and auto-oxidation degradation products or direct lysis of bacterial cells. Their broad spectrum of activity, non-specific mode of action and safety makes them attractive as antibacterial agents for various applications in medicine, agriculture and food preservation, especially where the use of conventional antibiotics is undesirable or prohibited. Moreover, the evolution of inducible FFA-resistant phenotypes is less problematic than with conventional antibiotics. The potential for commercial or biomedical exploitation of antibacterial FFAs, especially for those from natural sources, is discussed.