Comparative study on the antiviral activity of selected monoterpenes derived from essential oils

Essential oils are complex natural mixtures, their main constituents, e.g. terpenes and phenylpropanoids, being responsible for their biological properties. Essential oils from eucalyptus, tea tree and thyme and their major monoterpene compounds α‐terpinene, γ‐terpinene, α‐pinene, p‐cymene, terpinen‐4‐ol, α‐terpineol, thymol, citral and 1,8‐cineole were examined for their antiviral activity against herpes simplex virus type 1 (HSV‐1) in vitro. These essential oils were able to reduce viral infectivity by >96%, the monoterpenes inhibited HSV by about >80%. The mode of antiviral action has been determined, only moderate antiviral effects were revealed by essential oils and monoterpenes when these drugs were added to host cells prior to infection or after entry of HSV into cells. However, both essential oils and monoterpenes exhibited high anti‐HSV‐1 activity by direct inactivation of free virus particles. All tested drugs interacted in a dose‐dependent manner with herpesvirus particles thereby inactivating viral infection. Among the analysed compounds, monoterpene hydrocarbons were slightly superior to monoterpene alcohols in their antiviral activity, α‐pinene and α‐terpineol revealed the highest selectivity index. However, mixtures of different monoterpenes present in natural tea tree essential oil revealed a ten‐fold higher selectivity index and a lower toxicity than its isolated single monoterpenes. Copyright © 2009 John Wiley & Sons, Ltd.     

Anti‐leishmanial Activities of Extracts and Isolated Compounds from Drechslera rostrata and Eurotium tonpholium

The fungal extract of Drechslera rostrata and Eurotium tonpholium showed a significant anti‐leishmanial activity against Leishmania major; IC₅₀ was 28.8 and 28.2 μg/mL, respectively. Seven compounds, five from D. rostrata (H1–H5) and two from E. tonpholium (H6 and H7), were isolated and identified using different spectroscopic analysis including ¹HNMR, ¹³CNMR, Hetero‐nuclear multiple bond connectivity (HMBC), Hetero‐nuclear Multiple Quantum Correlation (HMQC), and EI‐MS. The isolated compounds are: di‐2‐ethylhexyl phthalate (1), (22E)‐5α,8α‐epidioxyergosta‐6,22‐diene‐3β‐ol (2),1,3,8‐trihydroxy‐6‐methyl‐nthraquinone (3), aloe‐emodine 8‐O‐glucopyranoside(4), 2R, 3R,4R,5R hexane 1, 2, 3, 4, 5, 6 hexole (Mannitol) (5), 1,8‐dihydroxy‐3‐methoxy‐6‐methyl‐anthraquinone (6) and 1, 4, 5‐trihydroxy‐7‐methoxy‐2‐methyl‐anthraquinone (7). However, compounds (1) and (6) showed activity against L. major with IC₅₀ of 3.2 and 10.38 µg/mL, respectively. On the other hand, oral administration of the two extracts (100 mg/kg) and compounds 1 and 6 (50 mg/kg) showed very good activity when compared with the anti‐leishmanial drug Pentostam (125 mg/kg). Interestingly, the complete heeling activity of the extracts and compounds (1) and (6) was obtained after 13–17 days of treatment, while complete healing activity of Pentostam was obtained after 28 days. No alteration on liver and kidney functions was recorded on animals treated with the two extracts for 15 consecutive days. Copyright © 2013 John Wiley & Sons, Ltd.     

Bioassay-guided evaluation of antinociceptive properties and chemical variability of the essential oil of Hyptis fruticosa

The composition of three samples of essential oil (EO) extracted from the leaves and flowers of Hyptis fruticosa (Lamiaceae) were investigated by GC/MS and GC‐FID. The variability of the constituents and biological activity were evaluated in the oil samples. Acetic acid‐induced abdominal constrictions and formalin‐induced pain tests in mice were used for screening the antinociceptive activity. The possible antagonism of the essential oils or morphine (MOR) antinociceptive effects by pretreatment with naloxone, showed no influence on the antinociceptive action of the oils in the acetic acid‐induced writhing test. All examined oil samples presented antinociceptive activity. The oil sample obtained from the leaves collected during the vegetative growth stage, near São Cristóvão at Sítio Tujubeba exhibited the highest effect. The same oil sample had a main percentage of 1,8‐cineole (18.70%). Nevertheless, the oil obtained from flowers collected at the same location, showed a significant difference (p < 0.05) in the response intensity in the first phase of paw licking (100 mg/kg) possibly due to the higher contents of α‐pinene (20.51%) and β‐pinene (13.64%). The results provide evidence for the use of H. fruticosa by traditional medicine practitioners in the management of pain. Copyright © 2011 John Wiley & Sons, Ltd.     

Antiplasmodial activity of isolated compounds from Carpesium divaricatum

The whole plants of Carpesium divaricatum are used in traditional medicine as an antipyretic, analgesic and vermifugic, including a topical application for sores and inflammation. In a previous paper, the isolation and structural elucidation of isolated ineupatorolides A from methanol extracts of C. rosulatum (Compositae) were reported. The present paper deals with the isolation and identification of antiplasmodial compounds from C. divaricatum in Carpesium spp. Five compounds, 1β,6α‐dihydroxy‐4(15)‐eudesmene [1], β‐dictyopterol [2], 2‐isopropenyl‐6‐acetyl‐8‐methoxy‐1,3‐benzodioxin‐4‐one [3], (3E,6E,10E,14E,18E)‐2,6,10,15,19,23‐hexamethyl‐3,6,10,14,18,22‐tetracosahexaen‐2‐ol [4] and neophytadiene [5], were isolated from the whole plants of C. divaricatum. The in vitro activity against P. falciparum strain D10 was assessed using the parasite lactate dehydrogenase assay method. The main antiplasmodial principle, 2‐isopropenyl‐6‐acetyl‐8‐methoxy‐1,3‐benzodioxin‐4‐one [3], has been isolated from C. divaricatum for the first time. Compound 3 exhibited an antiplasmodial activity with IC₅₀ values of 2.3 ± 0.3 μm . This is the first report on the antiplasmodial activity of the compounds from C. divaricatum. Copyright © 2009 John Wiley & Sons, Ltd.     

胡椒薄荷叶挥发油化学成分及活性分析

目的:研究胡椒薄荷Mentha piperita叶挥发油的化学成分及其生物活性,为胡椒薄荷资源的开发利用奠定基础。方法:采用超临界CO_2萃取法提取叶片挥发油,通过气相色谱-质谱联用技术(GC-MS)分析其化学成分,分别采用DPPH法和卤虫幼体研究其抗氧化活性及生物毒性,纸片扩散法及埃及伊蚊幼虫毒杀法评价其抗菌活性和杀虫活性。结果:用超临界CO_2萃取法提取得到的挥发油得率为0.089%,从中鉴定了11个化学成分,已鉴定出的组分占挥发油总量的93.0%,其中芳樟醇占总挥发油的49.9%,可以认为是其主要成分;挥发油对DPPH的半数抑制浓度(IC50)0.45 g·L~(-1),对卤虫幼体的半数致死浓度(LC50)526.0 mg·L~(-1);在挥发油质量浓度为10 g·L~(-1)时,对大肠埃希菌抑菌圈直径为(9±1)mm,对金黄色葡萄球菌效果不明显;对埃及伊蚊的LC50339.6 mg·L~(-1)。结论:胡椒薄荷叶挥发油对大肠埃希菌有一定的抑制作用,在抗氧化及杀虫方面具有一定活性,但是相对较弱,不宜用于杀虫剂产品开发;此外,胡椒薄荷叶挥发油具有弱的生物毒性。本研究为胡椒薄荷的开发利用提供了科学依据。     

Characterisation of Antimicrobial Extracts from Dandelion Root (Taraxacum officinale) Using LC‐SPE‐NMR

Plant extracts have traditionally been used as sources of natural antimicrobial compounds, although in many cases, the compounds responsible for their antimicrobial efficacy have not been identified. In this study, crude and dialysed extracts from dandelion root (Taraxacum officinale) were evaluated for their antimicrobial properties against Gram positive and Gram negative bacterial strains. The methanol hydrophobic crude extract (DRE3) demonstrated the strongest inhibition of microbial growth against Staphylococcus aureus, methicillin‐resistant S. aureus and Bacillus cereus strains. Normal phase (NP) fractionation of DRE3 resulted in two fractions (NPF4 and NPF5) with enhanced antimicrobial activity. Further NP fractionation of NPF4 resulted in two fractions (NPF403 and NPF406) with increased antimicrobial activity. Further isolation and characterisation of compounds in NPF406 using liquid chromatography solid phase extraction nuclear magnetic resonance LC‐SPE‐NMR resulted in the identification of 9‐hydroxyoctadecatrienoic acid and 9‐hydroxyoctadecadienoic acid, while the phenolic compounds vanillin, coniferaldehyde and p‐methoxyphenylglyoxylic acid were also identified respectively. The molecular mass of these compounds was confirmed by LC mass spectroscopy (MS)/MS. In summary, the antimicrobial efficacy of dandelion root extracts demonstrated in this study support the use of dandelion root as a source of natural antimicrobial compounds. Copyright © 2015 John Wiley & Sons, Ltd.     

Inhibitory Effect of Phenylbutanoid‐rich Zingiber cassumunar Extracts on Nitric Oxide Production by Murine Macrophage‐like RAW264.7 Cells

Four phenylbutanoids, (E)‐4‐(3,4‐dimethoxyphenyl)but‐3‐en‐l‐ol (I), (E)‐4‐(3,4‐dimethoxyphenyl)but‐3‐en‐l‐yl acetate (II), (E)‐1‐(3,4‐dimethoxyphenyl)butadiene (III) and (E)‐3‐(3,4‐dimethoxyphenyl)‐4‐[(E)‐3,4‐dimethoxystyryl]cyclohex‐1‐ene (IV), isolated from Zingiber cassumunar, were used as standard markers for quantitative determination and preparation of phenylbutanoid‐enriched Z. cassumunar extracts (PZEs). A reversed‐phase HPLC method was established for the simultaneous determination of the phenylbutanoids in Z. cassumunar extracts. Systematic extraction studies to maximize phenylbutanoid content revealed that hexane was the most appropriate solvent for extraction. A one‐step purification of the hexane crude extract of Z. cassumunar, using silica gel vacuum chromatography, provided the PZEs. The content of phenylbutanoids in the PZEs was up to 48.3% w/w dry weight. The anti‐inflammatory activity of PZEs via inhibition of nitric oxide production by murine macrophage‐like RAW264.7 cells was stronger than those of the four individual phenylbutanoids, the crude hexane extract and the essential oil of Z. cassumunar. Copyright © 2012 John Wiley & Sons, Ltd.     

Organ Accumulation in Mice After Inhalation of Single or Mixed Essential Oil Compounds

Essential oils are composed of multiple components. It is thought that the effect of essential oils is due to specific component ratios, which may differ from the original ratio when the essential oil is absorbed. However, very little detailed research exists in this area. We studied the distribution of essential oil components after inhalation of single and mixed components in mice. This research was done using four main components of Alpinia zerumbet (Pers.) B. L. Burtt. and R. M. Sm.: α‐pinene, p‐cymene, 1,8‐cineole, and limonene. After inhalation of single or mixed components for 90 min, component levels in the brain and liver of mice were measured. The results indicated that the amount of α‐pinene in the brain and liver was twofold greater after mixed‐component inhalation than that after single‐component inhalation. In a comparison of the components of the mixed inhalation, the ratio of α‐pinene increased to about three times that of 1,8‐cineole. It is thought that the absorption via the nasal mucus greatly influences this phenomenon. The results of this investigation of the bodily distribution of essential oil volatile components may provide clues for elucidating their action. Copyright © 2012 John Wiley & Sons, Ltd.     

气相色谱法测定岗松油中芳樟醇和桉油精的含量

 目的 建立岗松油中芳樟醇和桉油精的含量测定方法。方法 采用气相色谱法,FID检测器,以无水乙醇为溶剂,十一烷为内标,在SE-54毛细管色谱柱上,实现了芳樟醇和桉油精与各组分的基线分离。结果 芳樟醇在0.488-2.930 mg·mL^-1内,线性关系良好,回归方程为:Y=0.873 9X-0.0265,r=0.9999,回收率为100.8％(RSD=1.9％,n=5);桉油精在1.395-8.372 mg·mL^-1内,线性关系良好,回归方程为Y=0.931 8X-0.0076,r=0.9998,回收率为100.0％(RSD=1.7％,n=5)。结论 经方法学验证,该方法灵敏、准确、可靠,适用于岗松油中芳樟醇和桉油精的含量测定。     

α‐Glucosidase Inhibitors from the Stems of Embelia ribes

From the ethyl acetate extract of the stems of Embelia ribes (Myrsinaceae), a new alkenylresorcinol, embeliphenol A (1), together with 11 known compounds have been isolated. Their structures were elucidated on the basis of spectroscopic data. All compounds possessed significant α‐glucosidase inhibitory activity in a concentration‐dependent manner, except for 2 and 9. Compounds 1, 3–6, 8, and 12 showed more potent inhibitory activity, with IC₅₀ values ranging from 10.4 to 116.7 μM, than that of a positive control acarbose (IC₅₀, 214.5 μM). Copyright © 2014 John Wiley & Sons, Ltd.     

Osmitopsis asteriscoides (Asteraceae)-the antimicrobial activity and essential oil composition of a Cape-Dutch remedy

The essential oil composition and antimicrobial activity of Osmitopsis asteriscoides, a medicinal plant used in traditional herbal preparations in South Africa has been investigated. Three different antimicrobial methods (disc diffusion, minimum inhibitory concentration by micro-titer plate and time-kill studies) were comparatively evaluated against Candida albicans, Staphylococcus aureus and Pseudomonas aeruginosa. A preliminary screening was done using the disc diffusion method on nine bacterial and four fungal isolates. Minimum inhibitory concentrations showed some correlation with the disc diffusion method. However, time-kill studies appear to be a more superior method for determining antimicrobial activity of volatile compounds such as essential oils. Two moderately susceptible and one resistant organism were selected to further demonstrate the variability between the three methods. The antimicrobial activity of the essential oil, tested by means of time-kill methodology at concentrations ranging from 0.5 to 2% (v/v) indicate a strong fungicidal activity against Candida albicans and the oil was also found to be bacteriostatic against Staphylococcus aureus in a concentration-dependent manner. The essential oil rapidly reduced viable counts of Pseudomonas aeruginosa, but regrowth was noted after 240 min. The results have been generated in duplicate in separate microbiology laboratories using different time-kill methods and the results are congruent. The two major essential oil components camphor and 1,8-cineole were investigated indicating the positive antimicrobial efficacy of 1,8-cineole independently and in combination with camphor. In addition to (-)-camphor and 1,8-cineole, 40 compounds were identified by GC-MS in the hydro-distilled essential oil. The high concentration of cineole and camphor and their synergistic effect is presented as a possible explanation for the traditional use of Osmitopsis asteriscoides for treating microbe-related illnesses.     

The spasmolytic activity of the essential oil of Thymus baeticus boiss in rats

Gas chromatography and GC/MS studies of Thymus baeticus Boiss essential oil showed its major component to be 1,8-cineole. The essential oil was found to present a marked spasmolytic activity in rat duodenum against acetylcholine via a non-competitive type of inhibition. This action was not related to its major component, 1,8-cineole.     

Spasmolytic activity of Thymus membranaceus essential oil

The spasmolytic activity of Thymus membranaceus essential oil in the duodenum isolated from rat has been investigated. The qualitative and quantitative composition of the essential oil was studied. The essential oil affects the duodenum in two ways, showing a spasmogenic action (due to 1,8-cineole) and, on the other hand, an antagonistic non-competitive effect against the contractions by acetylcholine (due to the phenols and hydrocarbons).     

Pimarane‐type Diterpenes Obtained by Biotransformation: Antimicrobial Properties Against Clinically Isolated Gram‐positive Multidrug‐resistant Bacteria

The present study describes the antimicrobial activity of five pimarane‐type diterpenes obtained by fungal biotransformation against several nosocomial multidrug‐resistant bacteria. Among the investigated metabolites, ent‐8(14),15‐pimaradien‐3β‐ol was the most active compound, with very promising minimal inhibitory concentration values (between 8.0 and 25.0 µg mL^?1). Time‐kill assays using this metabolite against Staphylococcus aureus (HCRP180) revealed that this compound exerted its bactericidal effect within 24 h at all the evaluated concentrations (8.0, 16.0, and 24.0 µg mL^?1). When this metabolite was associated with vancomycin at their minimal bactericidal concentration values, the resulting combination was able to drastically reduce the number of viable strains of S. aureus within the first 6 h, compared with these chemicals alone. The checkerboard assays conducted against this microorganism did not evidence any synergistic effects when this same combination was employed. In conclusion, our results point out that ent‐8(14),15‐pimaradien‐3β‐ol is an important metabolite in the search for new effective antimicrobial agents. Copyright © 2012 John Wiley & Sons, Ltd.     

短柱八角和假地枫皮果皮挥发油的气相色谱-质谱分析

用GC-MS法对短柱八角和假地枫皮果皮的挥发油进行分析,检出75个成分,鉴定其中66个化合物。柠檬烯和芳樟醇在两种挥发油中的含量均较高,且短柱八角果皮挥发油中尚含较多的1,8-桉叶素和萜品烯醇-4。     

Carvacrol and human health: A comprehensive review

Carvacrol (CV) is a phenolic monoterpenoid found in essential oils of oregano (Origanum vulgare), thyme (Thymus vulgaris), pepperwort (Lepidium flavum), wild bergamot (Citrus aurantium bergamia), and other plants. Carvacrol possesses a wide range of bioactivities putatively useful for clinical applications such antimicrobial, antioxidant, and anticancer activities. Carvacrol antimicrobial activity is higher than that of other volatile compounds present in essential oils due to the presence of the free hydroxyl group, hydrophobicity, and the phenol moiety. The present review illustrates the state‐of‐the‐art studies on the antimicrobial, antioxidant, and anticancer properties of CV. It is particularly effective against food‐borne pathogens, including Escherichia coli, Salmonella, and Bacillus cereus. Carvacrol has high antioxidant activity and has been successfully used, mainly associated with thymol, as dietary phytoadditive to improve animal antioxidant status. The anticancer properties of CV have been reported in preclinical models of breast, liver, and lung carcinomas, acting on proapoptotic processes. Besides the interesting properties of CV and the toxicological profile becoming definite, to date, human trials on CV are still lacking, and this largely impedes any conclusions of clinical relevance.     

β‐Bisabolene,a Sesquiterpene from the Essential Oil Extract of Opoponax (Commiphora guidottii), Exhibits Cytotoxicity in Breast Cancer Cell Lines

The essential oils from Commiphora species have for centuries been recognized to possess medicinal properties. Here, we performed gas chromatography‐mass spectrometry on the essential oil from opoponax (Commiphora guidotti) and identified bisabolene isomers as the main constituents of this essential oil. Opoponax essential oil, a chemical component; β‐bisabolene and an alcoholic analogue, α‐bisabolol, were tested for their ability to selectively kill breast cancer cells. Only β‐bisabolene, a sesquiterpene constituting 5% of the essential oil, exhibited selective cytotoxic activity for mouse cells (IC₅₀ in normal Eph4: >200 µg/ml, MG1361: 65.49 µg/ml, 4T1: 48.99 µg/ml) and human breast cancer cells (IC₅₀ in normal MCF‐10A: 114.3 µg/ml, MCF‐7: 66.91 µg/ml, MDA‐MB‐231: 98.39 µg/ml, SKBR3: 70.62 µg/ml and BT474: 74.3 µg/ml). This loss of viability was because of the induction of apoptosis as shown by Annexin V‐propidium iodide and caspase‐3/7 activity assay. β‐bisabolene was also effective in reducing the growth of transplanted 4T1 mammary tumours in vivo (37.5% reduction in volume by endpoint). In summary, we have identified an anti‐cancer agent from the essential oil of opoponax that exhibits specific cytotoxicity to both human and murine mammary tumour cells in vitro and in vivo, and this warrants further investigation into the use of β‐bisabolene in the treatment of breast cancers. Copyright © 2015 John Wiley & Sons, Ltd.     

Selective antileishmania activity of 13,28‐epoxy‐oleanane and related triterpene saponins from the plant families Myrsinaceae,Primulaceae, Aceraceae and Icacinaceae

Maesa saponins with the 13,28‐epoxy‐oleanane triterpene core skeleton were described recently to possess strong and selective in vitro and in vivo antileishmania activity. In the absence of direct chemical derivatization possibilities, a structure‐based literature search was carried out to explore a structure‐activity relationship. Crude alcohol extracts from several plant species of Myrsinaceae, Primulaceae, Aceraceae and Icacinaceae were evaluated for in vitro activity against Leishmania infantum intracellular amastigotes and cytotoxicity on MRC‐5_SV2 cells, while the saponin content was evaluated qualitatively by TLC. A clear correlation was found between the presence of close analogue 13,28‐epoxy‐oleanane triterpene saponins and potent and selective antileishmania activity. This was most striking in Maesa species, except for M. macrosepala. Interesting activities were also found in extracts that did not exactly match the TLC characteristics of the Maesa saponin references, as was the case for Ardisia angusta, A. amherstiana, A. caudata, A. gigantifolia, A. roseiflora, Myrsine affinis, Acer brevipes and A. laurinum var. petelotii. This study indicates that the 13,28‐epoxy‐oleanane triterpene moiety is essential for selective antileishmania potential and that several other plant species could still be explored for antileishmania drug discovery. Copyright © 2009 John Wiley & Sons, Ltd.     

Essential Oil of Juniperus communis subsp. alpina (Suter) Čelak Needles: Chemical Composition,Antifungal Activity and Cytotoxicity

Essential oils are known to possess antimicrobial activity against a wide spectrum of bacteria and fungi. In the present work the composition and the antifungal activity of the oils of Juniperus communis subsp. alpina (Suter) ?elak were evaluated. Moreover, the skin cytotoxicity, at concentrations showing significant antifungal activity, was also evaluated. The oils were isolated by hydrodistillation and analysed by gas chromatography and gas chromatography–mass spectrometry. Minimal inhibitory concentration (MIC) and minimal lethal concentration (MLC) were used to evaluate the antifungal activity of the oil against dermatophytes (Epidermophyton floccosum, Microsporum canis, M. gypseum, Trichophyton mentagrophytes, T. mentagrophytes var. interdigitale, T. rubrum, T. verrucosum), yeasts (Candida albicans, C. guillermondii, C. krusei, C. parapsilosis, C. tropicalis, Cryptococcus neoformans) and Aspergillus species (Aspergillus flavus, A. fumigatus, A. niger). Cytotoxicity was tested in HaCaT keratinocytes through the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay. Essential oil of J. communis subsp. alpina needles was predominantly composed of monoterpene hydrocarbons (78.4%), with the main compounds being sabinene (26.2%), α‐pinene (12–9%) and limonene (10.4%). Results concerning the antifungal activity demonstrated the potential of needle oil against dermatophytes, particularly for Microsporum canis and Trichophyton rubrum with MIC and MLC of 0.32 μL/mL. Furthermore, evaluation of cell viability showed no significant cytotoxicity in HaCaT keratinocytes at concentrations between 0.32 and 0.64 μL/mL. These results show that it is possible to find appropriate doses of J. communis subsp. alpina oil with both antifungal activity and a very low detrimental effect on keratinocytes. Copyright © 2012 John Wiley & Sons, Ltd.