Monoterpenoid accumulation in 1,8-cineole, terpinolene and terpinen-4-ol chemotypes of Melaleuca alternifolia seedlings

Ethnopharmacology, Biological Activity and Phytochemistry of Scaevola spinescens

Scaevola spinescens is endemic to Australia and has traditionally been used by Aboriginal and Torres Strait Islander communities to treat a variety of conditions including colds, flu, fever, stomach pain, urinary disorders, sores, tinea, leprosy, and cancer. Extracts prepared from S. spinescens are non-toxic and have been linked with various medicinal properties including antiviral, antibacterial, anti-inflammatory, and anticancer activities. These studies support the ethnopharmacological use of S. spinescens by Indigenous peoples of Australia and highlight the need for further investigations on the plant for potential use in pharmaceutical and food applications. This review provides a comprehensive, up-to-date review of the literature on S. spinescens focusing on the traditional use, medicinal properties, phytochemicals, and factors that affect their composition during pre-treatment and extraction, as well as providing a framework for future studies of the plant.

Fabrication of Antibacterial Nanofibrous Membrane Infused with Essential Oil Extracted from Tea Tree for Packaging Applications

Nanofibers made by electrospinning are being applied to an unlimited number of applications. In this paper, we propose the fabrication of antimicrobial functional nanofibers infused with essential oil for packaging applications that can extend the shelf-life of fruits. The morphology of nanofibers with different concentrations of essential oil was characterized by SEM and mechanical enhancement was confirmed via universal testing machine (UTM). The surface chemistry and crystalline of the nanofibers were investigated by FTIR and XRD, respectively. The CO₂ reduction study was carried out using a hand-made experimental apparatus and nanofiber hydrophobicity, which can prevent moisture penetration from the outside, was evaluated by contact angle. Antimicrobial properties of the functional nanofibers were estimated by using Gram-negative/positive bacteria. The cytotoxicity of the functional nanofibers was studied using fibroblast cells. Furthermore, this study investigated how long the shelf-life of tomatoes was extended. The nanofibers could serve as a multifunctional packaging, as an emerging technology in agricultural products, and even contribute to a better quality of various distributed agricultural products.

Oxidative stress and mitochondrial impairment mediated apoptotic cell death induced by terpinolene in Schizosaccharomyces pombe

Terpinolene is one of the most abundant monoterpenes used as a food supplement or odorant in cosmetics and the pharmaceutical industry. In this study, we aimed to assess apoptotic, oxidative and cytotoxic effects of terpinolene. We used the fission yeast (Schizosaccharomyces pombe) as a promising uni-cellular model organism in molecular toxicology and cell death research, due to its resemblance to mammalian cells at the molecular level. After terpinolene exposure (200-800 mg L-1), the IC50 and LC50 were calculated as 349.17 mg L-1 and 593.87 mg L-1. Cells, stained with acridine orange/ethidium bromide and DAPI, showed apoptotic nuclear morphology, chromatin condensation and fragmentation. 2,7-Dichlorodihydrofluorescein diacetate (DCFDA) fluorescence gradually increased (1.5-2-fold increase) in correlation with increasing concentrations of terpinolene (200-800 mg L-1). Mitochondrial impairment at higher concentrations of terpinolene (400-800 mg L-1) was shown by Rhodamine 123 staining. Real-time PCR experiments showed significant increases (1.5-3-fold) in SOD1 and GPx1 levels (p < 0.05) as well as 2-2.5-fold increases (p < 0.05) in pro-apoptotic factors, Pca1 and Sprad9. The potential effects of terpinolene on programmed cell death and the underlying mechanisms were clarified in unicellular model fungi, Schizosaccharomyces pombe.

Transcriptome analysis of terpene chemotypes of Melaleuca alternifolia across different tissues

Plant chemotypes or chemical polymorphisms are defined by discrete variation in secondary metabolites within a species. This variation can have consequences for ecological interactions or the human use of plants. Understanding the molecular basis of chemotypic variation can help to explain how variation of plant secondary metabolites is controlled. We explored the transcriptomes of the 3 cardinal terpene chemotypes of Melaleuca alternifolia in young leaves, mature leaves, and stem and compared transcript abundance to variation in the constitutive profile of terpenes. Leaves from chemotype 1 plants (dominated by terpinen-4-ol) show a similar pattern of gene expression when compared to chemotype 5 plants (dominated by 1,8-cineole). Only terpene synthases in young leaves were differentially expressed between these chemotypes, supporting the idea that terpenes are mainly synthetized in young tissue. Chemotype 2 plants (dominated by terpinolene) show a greater degree of differential gene expression compared to the other chemotypes, which might be related to the isolation of plant populations that exhibit this chemotype and the possibility that the terpinolene synthase gene in M. alternifolia was derived by introgression from a closely related species, Melaleuca trichostachya. By using multivariate analyses, we were able to associate terpenes with candidate terpene synthases.

Effect of tea tree (Melaleuca alternifolia) oil as a natural antimicrobial agent in lipophilic formulations

There has been increased interest surrounding the use of tea tree oil (TTO) as a natural antimicrobial. In this study, the antimicrobial activity of TTO and its components were investigated in vitro and in a predominantly lipid-based personal care formulation. In vitro, TTO showed minimal inhibitory concentrations of 0.2% (for Saccharomyces cerevisiae and Pythium sulcatum), 0.4% (for Escherichia coli, Bacillus subtilis, and Rhizopus stolonifer), and 0.8% (for Botrytis cinerea). TTO at 0.08%-0.8% was often as efficient as parabens. Comparison of the antimicrobial activities of TTO components showed that terpinen-4-ol and γ-terpinene were generally most effective in inhibiting microbial growth. TTO activity in a personal care product was evaluated through air and water exposure, artificial inoculation, and shelf life studies. While TTO did not increase shelf life of unopened products, it decreased microbial load in products exposed to water and air. Results from this study support that antimicrobial activity of TTO can be attributed to varying levels of its components and that low levels of TTO were effective in reducing microbial growth during the use of the product. This study showed that TTO can act as a suitable preservative system within an oil-based formulation.

Near Infrared Spectroscopy Facilitates Rapid Identification of Both Young and Mature Amazonian Tree Species

Precise identification of plant species requires a high level of knowledge by taxonomists and presence of reproductive material. This represents a major limitation for those working with seedlings and juveniles, which differ morphologically from adults and do not bear reproductive structures. Near-infrared spectroscopy (FT-NIR) has previously been shown to be effective in species discrimination of adult plants, so if young and adults have a similar spectral signature, discriminant functions based on FT-NIR spectra of adults can be used to identify leaves from young plants. We tested this with a sample of 419 plants in 13 Amazonian species from the genera Protium and Crepidospermum (Burseraceae). We obtained 12 spectral readings per plant, from adaxial and abaxial surfaces of dried leaves, and compared the rate of correct predictions of species with discriminant functions for different combinations of readings. We showed that the best models for predicting species in early developmental stages are those containing spectral data from both young and adult plants (98% correct predictions of external samples), but even using only adult spectra it is still possible to attain good levels of identification of young. We obtained an average of 75% correct identifications of young plants by discriminant equations based only on adults, when the most informative wavelengths were selected. Most species were accurately predicted (75-100% correct identifications), and only three had poor predictions (27-60%). These results were obtained despite the fact that spectra of young individuals were distinct from those of adults when species were analyzed individually. We concluded that FT-NIR has a high potential in the identification of species even at different ontogenetic stages, and that young plants can be identified based on spectra of adults with reasonable confidence.

Intensive sampling identifies previously unknown chemotypes, population divergence and biosynthetic connections among terpenoids in Eucalyptus tricarpa

Australian members of the Myrtaceae produce large quantities of ecologically and economically important terpenes and display abundant diversity in both yield and composition of their oils. In a survey of the concentrations of leaf terpenes in Eucalyptus tricarpa (L.A.S. Johnson) L.A.S. Johnson & K.D. Hill, which were previously known from few samples, exceptional variability was found in composition. The aim was to characterize the patterns of variation and covariation among terpene components in this species and to use this information to enhance our understanding of their biosynthesis. There were marked discontinuities in the distributions of numerous compounds, including the overall proportions of mono- and sesquiterpenes, leading us to delineate three distinct chemotypes. Overall, positive covariation predominated, but negative covariation suggested competitive interactions involved in monoterpene synthesis. Two groups of covarying monoterpenes were found, each of which was positively correlated with a group of sesquiterpenes and negatively correlated with the alternate sesquiterpene group. These results imply substantial cross-talk between mono- and sesquiterpene biosynthesis pathways. However, only those compounds hypothesized to share final carbocation intermediates or post-processing steps were strongly positively correlated within chemotypes. This suggests that the broader patterns of covariation among groups of compounds may result from co-regulation of multiple biosynthetic genes, controlling the complex terpene profiles of the chemotypes of Eucalyptus.

The yield of essential oils in Melaleuca alternifolia (Myrtaceae) is regulated through transcript abundance of genes in the MEP pathway

Medicinal tea tree (Melaleuca alternifolia) leaves contain large amounts of an essential oil, dominated by monoterpenes. Several enzymes of the chloroplastic methylerythritol phosphate (MEP) pathway are hypothesised to act as bottlenecks to the production of monoterpenes. We investigated, whether transcript abundance of genes encoding for enzymes of the MEP pathway were correlated with foliar terpenes in M. alternifolia using a population of 48 individuals that ranged in their oil concentration from 39 -122 mg.g DM⁻¹. Our study shows that most genes in the MEP pathway are co-regulated and that the expression of multiple genes within the MEP pathway is correlated with oil yield. Using multiple regression analysis, variation in expression of MEP pathway genes explained 87% of variation in foliar monoterpene concentrations. The data also suggest that sesquiterpenes in M. alternifolia are synthesised, at least in part, from isopentenyl pyrophosphate originating from the plastid via the MEP pathway.

Antimicrobial and antioxidant activities of essential oils of Satureja thymbra growing wild in Libya

The composition of essential oil isolated from Satureja thymbra, growing wild in Libya, was analyzed by GC and GC-MS. The essential oil was characterized by γ-terpinene (39.23%), thymol (25.16%), p-cymene (7.17%) and carvacrol (4.18%) as the major constituents. Antioxidant activity was analyzed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method. It possessed strong antioxidant activity (IC50 = 0.0967 mg/mL). The essential oil was also screened for its antimicrobial activity against eight bacterial and eight fungal species, showing excellent antimicrobial activity against the microorganisms used, in particular against the fungi. The oil of S. thymbra showed bacteriostatic activity at 0.001-0.1 mg/mL and was bactericidal at 0.002-0.2 mg/mL; fungistatic effects at 0.001-0.025 mg/mL and fungicidal effects at 0.001-0.1 mg/mL. The main constituents thymol, carvacrol and γ-terpinene also showed strong antimicrobial activity. The commercial fungicide bifonazole showed much lower antifungal activity than the tested oil.

An examination of the medicinal potential of Scaevola spinescens: Toxicity, antibacterial, and antiviral activities

Background:

Scaevola spinescens is an endemic Australian native plant with a history of use as a medicinal agent by indigenous Australians. Yet the medicinal bioactivities of this plant are poorly studied.

Materials and Methods:

S. spinescens solvent extracts were tested for antimicrobial activity, antiviral activity and toxicity in vitro.

Results:

All extracts displayed antibacterial activity in the disc diffusion assay. The methanol extract proved to have the broadest specificity, inhibiting the growth of 7 of the 14 bacteria tested (50%). The water, ethyl acetate, chloroform, and hexane extracts inhibited the growth of 6 (42.9%), 5 (35.7%), 5 (35.7%), and 4 (28.6%) of the 14 bacteria tested, respectively. S. spinescens methanolic extracts were equally effective against Gram-positive (50%) and Gram-negative bacteria (50%). All other extracts were more effective at inhibiting the growth of Gram-negative bacteria. All extracts also displayed antiviral activity in the MS2 plaque reduction assay with the methanol, water, ethyl acetate, chloroform, and hexane extracts inhibiting 95.2 ± 1.8%, 72.3 ± 6.3%, 82.6 ± 4.5%, 100 ± 0% and 47.7 ± 12.9% of plaque formation, respectively. All S. spinescens extracts were nontoxic in the Artemia fransiscana bioassay with no significant increase in mortality induced by any extract at 24 and 48 h. The only increase in mortality was seen for the water extract at 72 h, although even this extract displayed low toxicity, inducing only 41.7 ± 23.3% mortality.

Conclusions:

The lack of toxicity of the S. spinescens extracts and their inhibitory bioactivity against bacteria and viruses validate the Australian Aboriginal usage of S. spinescens and indicates its medicinal potential.

Chemotypic variation of essential oils in the medicinal plant, Anemopsis californica

Anemopsis californica (Saururaceae) commonly called yerba mansa, is an important medicinal plant in many deserts in the southwestern region of North America. Populations of A. californica, collected throughout New Mexico, were examined for chemical variability in roots and rhizomes for select monocyclic (cymene, limonene, piperitone and thymol) and bicyclic (alpha-pinene, 1,8-cineole and myrtenol) monoterpenoid and phenylpropanoid (methyleugenol, isoeugenol and elemicin) derived essential oil components. Three distinct chemotypes were detected using a hierarchical clustering analysis on the concentration of 10 different analytes in three individuals from each of 17 populations. One chemotype was characterized by high elemicin concentrations, a second chemotype by high methyleugenol concentrations and the third by high piperitone and thymol concentrations. Steam distilled oil was used to screen for anticancer bioactivity. A. californica root oils demonstrated anti-proliferative activity against AN3CA and HeLa cells in vitro but no activity against lung, breast, prostate or colon cancer cells. The IC(50) values for the root oil were 0.056% and 0.052% (v/v) for the AN3CA and HeLa cells, respectively.

Early ontogenetic patterns in chemical defense in Plantago (Plantaginaceae): genetic variation and trade-offs

Predictions based on the plant age and growth-differentiation balance hypotheses of defense were tested in two congeneric species, Plantago lanceolata and P. major, by quantifying iridoid glycosides, defensive chemicals, in seeds and leaves during the first 6 wk of growth. Concentrations decreased from the seed to 2-wk-old seedling stage in P. lanceolata, but increased during this period in P. major. In both species, levels were similar for 2- and 4-wk-old plants, then significantly increased from 4 to 6 wk. Genetic variation in the ontogeny of iridoid glycoside production was significant in both species at the maternal family level and at the population level. To examine whether allocation costs could explain the low production of iridoid glycosides in seedlings, relationships between growth and defense (iridoid glycosides) were characterized. Growth and defense had a positive or null relationship in all age groups, indicating that there was no trade-off in these plants at any age. This study provides some support for the growth-differentiation balance hypothesis, but offers no support for the plant age hypothesis. Measuring how herbivory affects plant fitness at different ontogenetic stages may shed light on these patterns in Plantago and on the evolution of the ontogeny of defense.

Chemical Composition and Bioactivity of the Leaf Oil of Calyptranthes pallens (Poir.) Griseb. from Abaco Island, Bahamas

The leaf oil of Calyptranthes pallens was obtained by hydrodistillation and analyzed by GC/MS. The most abundant oil components were the monoterpenoids α-pinene (24.7%), α-terpineol (13.8%), and trans-pinocarveol (11.6%). The antimicrobial activity against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger, and the in-vitro cytotoxicity of the oil on Hep G2, MDA-MB-231, Hs 578T, and PC-3 human tumor cells were also examined.

Regulation of oil accumulation in single glands of Eucalyptus polybractea

The accumulation of terpenoid oil was examined in the leaves of Eucalyptus polybractea at scales ranging from individual oil glands to the whole plant. Variations in oil composition and concentration of oil were measured and related to both morphological and physiological parameters. Within a plant, all glands produced oil of broadly similar composition that was not regulated by leaf age or the position of the gland within the leaf. There were, however, distinct differences between plants, suggesting that composition is controlled primarily at the whole-plant level. Oil concentration, too, was regulated primarily at the whole-plant level and was limited by gland capacity. Gland capacity was linked to leaf area and thickness, the final products of leaf expansion. Leaf and plant oil composition is determined not by a mosaic of glands specializing in producing a single or a small group of compounds, but rather by glands with remarkably similar capacities for terpenoid biosynthesis, although oil concentration, limited by gland capacity, may be linked to leaf expansion rather than biosynthetic capacity.

NATURAL HEALTH PRODUCTS AND DRUG DISPOSITION

Botanicals such as herbal products (HPs) and nutraceuticals (NCs) are often regarded as low risk because of their long history of human use. Anecdotal and literature reports of adverse drug events (ADEs) and clinical studies with HPs are increasing, but many of the reports are incomplete and contradictory. These reports need to identify confounding factors and explain contradictory findings if they are to help health care professionals or patients understand what risks are involved. HPs are complex botanicals, not single-active ingredient (SAI) products. Studies can be confounded by different manufacturing processes and formulations, including cosmetics and food supplements; environment; chemotypes; misidentification or adulteration; and factors associated with the patient or user population such as use, total drug load, and genetics. Future studies need to be conducted with characterized product that includes all commercially available related products. Clinical trials should be relevant to the user population and take into account the confounding factors that may influence the interpretation of the findings.

The capacity for thermal protection of photosynthetic electron transport varies for different monoterpenes in Quercus ilex

Heat stress resistance of foliar photosynthetic apparatus was investigated in the Mediterranean monoterpene-emitting evergreen sclerophyll species Quercus ilex. Leaf feeding with fosmidomycin, which is a specific inhibitor of the chloroplastic isoprenoid synthesis pathway, essentially stopped monoterpene emission and resulted in the decrease of the optimum temperature of photosynthetic electron transport from approximately 38 degrees C to approximately 30 degrees C. The heat stress resistance was partly restored by fumigation with 4 to 5 nmol mol(-1) air concentrations of monoterpene alpha-pinene but not with fumigations with monoterpene alcohol alpha-terpineol. Analyses of monoterpene physicochemical characteristics demonstrated that alpha-pinene was primarily distributed to leaf gas and lipid phases, while alpha-terpineol was primarily distributed to leaf aqueous phase. Thus, for a common monoterpene uptake rate, alpha-terpineol is less efficient in stabilizing membrane liquid-crystalline structure and as an antioxidant in plant membranes. Furthermore, alpha-terpineol uptake rate (U) strongly decreased with increasing temperature, while the uptake rates of alpha-pinene increased with increasing temperature, providing a further explanation of the lower efficiency of thermal protection by alpha-terpineol. The temperature-dependent decrease of alpha-terpineol uptake was both due to decreases in stomatal conductance, g(w), and increased volatility of alpha-terpineol at higher temperature that decreased the monoterpene diffusion gradient between the ambient air (F(A)) and leaf (F(I); U = g(w)[F(A) - F(I)]). Model analyses suggested that alpha-pinene reacted within the leaf at higher temperatures, possibly within the lipid phase, thereby avoiding the decrease in diffusion gradient, F(A) - F(I). Thus, these data contribute to the hypothesis of the antioxidative protection of leaf membranes during heat stress by monoterpenes. These data further suggest that fumigation with the relatively low atmospheric concentrations of monoterpenes that are occasionally observed during warm windless days in the Mediterranean canopies may significantly improve the heat tolerance of nonemitting vegetation that grows intermixed with emitting species.

Inhibition of acetylcholinesterase by Tea Tree oil

Pediculosis is a widespread condition reported in schoolchildren. Treatment most commonly involves the physical removal of nits using fine-toothcombs and the chemical treatment of adult lice and eggs with topical preparations. The active constituents of these preparations frequently exert their effects through inhibition of acetylcholinesterase (AChE, EC 3.1.1.7). Increasing resistance to many preparations has led to the search for more effective treatments. Tea Tree oil, otherwise known as Melaleuca oil, has been added to several preparations as an alternative treatment of head lice infestations. In this study two major constituents of Tea Tree oil, 1,8-cineole and terpinen-4-ol, were shown to inhibit acetylcholinesterase at IC50 values (inhibitor concentrations required to give 50% inhibition) of 0.04 and 10.30 mM, respectively. Four samples of Tea Tree oil tested (Tisserand, Body Treats, Main Camp and Irish Health Culture Association Pure Undiluted) showed anticholinesterase activity at IC50 values of 0.05, 0.10, 0.08 and 0.11 microL mL(-1), respectively. The results supported the hypothesis that the insecticidal activity of Tea Tree oil was attributable, in part, to the anticholinesterase activity of Tea Tree oil.