Pinus halepensis, Pinus pinaster, Pinus pinea and Pinus sylvestris Essential Oils Chemotypes and Monoterpene Hydrocarbon Enantiomers, before and after Inoculation with the Pinewood Nematode Bursaphelenchus xylophilus

Limonene Enantiomeric Ratios from Anthropogenic and Biogenic Emission Sources

Emissions from volatile chemical products (VCPs) have been identified as contributors to air quality degradation in urban areas. Limonene can be a tracer compound for VCPs containing fragrances in densely populated regions, but limonene is also emitted from conifers that are planted in urban areas. This creates challenges for using limonene to estimate VCP emissions. In this study, the -/+ enantiomeric ratios of limonene from VCP and conifer emission sources were quantified to evaluate if this measurement could be used to aid in source apportionment and emission inventory development. Samples were analyzed using a gas chromatograph equipped with a chiral column and mass spectrometry. The results demonstrate that limonene exhibits distinct enantiomeric ratios when sourced from VCPs versus conifers. (+)-Limonene was dominant in VCP sources (>97%), which was not universally true for conifer sources. The results were compared to those of air samples collected outside at two locations and indoors. The levels of (-)-limonene in outdoor air in Irvine and Portland and in indoor air were 50%, 22%, and 4%, respectively. This suggests outdoor limonene had both VCP and plant emission sources while indoor air was dominated by VCP sources. This study demonstrates the potential utility of enantiomeric analysis for improving VCP emission estimates in urban areas.

Essential Oil Compositions of Pinus Species (P. contorta Subsp. contorta, P. ponderosa var. ponderosa, and P. flexilis); Enantiomeric Distribution of Terpenoids in Pinus Species

Pinus species are important in traditional medicine throughout their ranges, and pine essential oils are of interest in aromatherapy and as topical treatments. In this work, the leaf (needle) essential oils of Pinus ponderosa var. ponderosa and Pinus contorta subsp. contorta from Oregon and Pinus flexilis growing in Idaho, have been obtained by hydrodistillation and analyzed by gas chromatographic techniques. The leaf essential oil of P. ponderosa was dominated by β-pinene (21.5-55.3%), methyl chavicol (8.5-41.5%), α-pinene (3.6-9.6%), δ-3-carene (3.6-6.2%), and α-terpineol (1.4-5.3%). The major components of P. contorta essential oil were β-phellandrene (23.8%), terpinen-4-ol (11.0%). The essential oil of P. flexilis was dominated by α-pinene (37.1%), β-pinene (21.9%), bornyl acetate (12.8%), and camphene (8.5%). Chiral gas chromatography revealed the enantiomeric ratios of α-pinene and limonene to be variable, but (-)-β-pinene predominated in Pinus essential oils.

Anthracnose Disease Control and Postharvest Quality of Hass Avocado Stored in Biobased PLA/PBAT/Pine Essential Oil/Chitosan Active Packaging Nets

For sale in the domestic market, Hass avocados are kept in non-biodegradable plastic nets and stored at an ambient temperature. The fungus Colletotrichum gloeosporioides can cause important losses at this stage. Consequently, formulations based on polylactic acid (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) 60/40 biodegradable blends added with pine essential oil (PEO) at 10, 12, 14, and 20% and coated with 1% chitosan (CH) were used for the elaboration of nets, which were evaluated on C. gloeosporioides and Rhizopus stolonifer on nutrient media and fruit and on the ripening behavior of Hass avocados at ambient temperature. The spore germination stage of C. gloeosporioides was the most extensively damaged (78% inhibition). The incidence of anthracnose was notably reduced by almost 80% in the avocados stored in the 60/40 PLA/PBAT nets coated with 1% CH. The overall values regarding weight loss, °Brix, and dry matter were c.a. 23.5%, 7.5, and 24.5%, respectively. The changes in firmness, color, and CO₂ production were particularly associated with the initial harvest index and storage temperature rather than with the nets. In future research, essays on nets should include evaluations at the commercial levels.

Chemical Characterization and Bioactivity of Commercial Essential Oils and Hydrolates Obtained from Portuguese Forest Logging and Thinning

Essential oils (EOs) and hydrolates (Hds) are natural sources of biologically active ingredients with broad applications in the cosmetic industry. In this study, nationally produced (mainland Portugal and Azores archipelago) EOs (11) and Hds (7) obtained from forest logging and thinning of Eucalyptus globulus, Pinus pinaster, Pinus pinea and Cryptomeria japonica, were chemically evaluated, and their bioactivity and sensorial properties were assessed. EOs and Hd volatiles (HdVs) were analyzed by GC-FID and GC-MS. 1,8-Cineole was dominant in E. globulus EOs and HdVs, and α- and β-pinene in P. pinaster EOs. Limonene and α-pinene led in P. pinea and C. japonica EOs, respectively. P. pinaster and C. japonica HVs were dominated by α-terpineol and terpinen-4-ol, respectively. The antioxidant activity was determined by DPPH, ORAC and ROS. C. japonica EO showed the highest antioxidant activity, whereas one of the E. globulus EOs showed the lowest. Antimicrobial activity results revealed different levels of efficacy for Eucalyptus and Pinus EOs while C. japonica EO showed no antimicrobial activity against the selected strains. The perception and applicability of emulsions with 0.5% of EOs were evaluated through an in vivo sensory study. C. japonica emulsion, which has a fresh and earthy odour, was chosen as the most pleasant fragrance (60%), followed by P. pinea emulsion (53%). In summary, some of the studied EOs and Hds showed antioxidant and antimicrobial activities and they are possible candidates to address the consumers demand for more sustainable and responsibly sourced ingredients.

A Bursaphelenchus xylophilus pathogenic protein Bx-FAR-1, as potential control target, mediates the jasmonic acid pathway in pines

BACKGROUND

The pine wilt disease (PWD) caused by Bursaphelenchus xylophilus is a devastating forest disease and its pathogenesis remains unclear. Secreted enzymes and proteins are important pathogenicity determinants and Bx-FAR-1 is an important pathogenic protein involved in the interaction between pine and B. xylophilus. However, the function of the Bx-FAR-1 protein in monitoring and prevention PWD remains unknown.

RESULTS

We found a small peptide of B. xylophilus effector Bx-FAR-1 is sufficient for immunosuppression function in Nicotiana benthamiana. Transient expression of Bx-FAR-1 in N. benthamiana revealed that nuclear localization is required for its function. The results of the ligand binding test showed that Bx-FAR-1 protein had the ability to bind fatty acid and retinol. We demonstrated that Bx-FAR-1 targeted to the nuclei of Pinus thunbergii using the polyclonal antibody by immunologic approach. The content of jasmonic acid (JA) was significantly increased in P. thunbergii infected with B. xylophilus when Bx-FAR-1 was silenced. We identified an F-box protein as the host target of Bx-FAR-1 by yeast two-hybrid and co-immunoprecipitation. Moreover, we found that Pt-F-box-1 was up-regulated during B. xylophilus infection and the expression of Pt-F-box-1 was increased in Bx-FAR-1 double-stranded RNA (dsRNA)-treated host pines.

CONCLUSION

This study illustrated that Bx-FAR-1 might mediate the JA pathway to destroy the immune system of P. thunbergii, indicating that PWN likely secretes effectors to facilitate parasitism and promote infection, which could better reveal the pathogenesis mechanisms of B. xylophilus and would be beneficial for developing disease control strategies.

Variations in Essential oils from South Siberian conifers of the Pinaceae family: new data towards identification and quality control

Conifer essential oils have been used for centuries in traditional medicine, and nowadays they are of special interest for official medicine, aromatherapy and perfumery. In the present work, comprehensive information is given on the composition of essential oils prepared from the twigs of the conifer trees of the pine family ( Pinaceae ): Abies sibirica Ledeb., Larix sibirica Ledeb., Picea obovata Ledeb., Pinus sibirica Du Tour, Pinus sylvestris L. A total of 50 samples of essential oils have been studied. The samples were prepared during vegetation stage in the time period 1998-2012 from the growing wild trees in the South part of the Western Siberia (Russian Federation) and neighboring territories of Republic of Kazakhstan within the area with geographical coordinates LAT 49.180012-57.908583 and LON 83.213217-91.258717 at elevation of 82-2070 m above sea level. All the essential oil samples were obtained from freshly collected plant raw material by steam distillation at atmospheric pressure in stainless steel apparatus, which had been specially designed for field research. All the chromatographic profiles were prepared from authentic samples whose voucher specimens are deposited at the Central Siberian Botanical Garden of the Siberian Branch of the Russian Academy of Sciences (NS). The following information for each sample is provided: (1) date and location of the plant raw material collecting, indicating administrative areas and the exact geographic coordinates; (2) yield of essential oil, (3) chemical composition of the essential oil sample based on GC-MS experiments using full mass-spectra (EI, 70 eV) and linear retention indices of the components, (4) results of GC-FID quantification based on internal standards and response factors, (5) enantiomeric composition of the main components based on GC×GC experiments using the 2nd column with cyclodextrine-based chiral selector, (6) GC profile of the high-boiling fractions indicating the characteristic sesquiterpenoids. Therefore, this study provides reliable information about the variability and true composition of the Siberian conifer oils, and the experimental data given can serve as reference chromatographic profiles of volatile substances to solve the problems of quality, authenticity and safety.

Phytochemicals as Biopesticides against the Pinewood Nematode Bursaphelenchus xylophilus: A Review on Essential Oils and Their Volatiles

The impacts of a rapidly changing environment together with the growth in global trade activities has promoted new plant pest pandemic events in forest ecosystems. The pinewood nematode (PWN), Bursaphelenchus xylophilus, causes strong worldwide economic and ecological impacts. Direct control is performed through trunk injection of powerful nematicides, however many of these (hemi)synthetic compounds have raised ecological and human health concerns for affecting non-target species and accumulating in food products. As sustainable alternatives, essential oils (EOs) have shown very promising results. In this work, available literature on the direct activity of EOs against PWN is reviewed, as a contribution to advance the search for safer and greener biopesticides to be used in sustainable PWD pest management strategies. For the first time, important parameters concerning the bioassays performed, the PWNs bioassayed, and the EOs used are summarized and comparatively analyzed. Ultimately, an overview of the chemical composition of the most active EOs allowed to uncover preliminary guidelines for anti-PWN EO efficiency. The analysis of important information on the volatile phytochemicals composing nematicidal EOs provides a solid basis to engineer sustainable biopesticides capable of controlling the PWN under an integrated pest management framework and contributes to improved forest health.

Insights Into the Mechanisms Implicated in Pinus pinaster Resistance to Pinewood Nematode

Pine wilt disease (PWD), caused by the plant-parasitic nematode Bursaphelenchus xylophilus, has become a severe environmental problem in the Iberian Peninsula with devastating effects in Pinus pinaster forests. Despite the high levels of this species' susceptibility, previous studies reported heritable resistance in P. pinaster trees. Understanding the basis of this resistance can be of extreme relevance for future programs aiming at reducing the disease impact on P. pinaster forests. In this study, we highlighted the mechanisms possibly involved in P. pinaster resistance to PWD, by comparing the transcriptional changes between resistant and susceptible plants after infection. Our analysis revealed a higher number of differentially expressed genes (DEGs) in resistant plants (1,916) when compared with susceptible plants (1,226). Resistance to PWN is mediated by the induction of the jasmonic acid (JA) defense pathway, secondary metabolism pathways, lignin synthesis, oxidative stress response genes, and resistance genes. Quantification of the acetyl bromide-soluble lignin confirmed a significant increase of cell wall lignification of stem tissues around the inoculation zone in resistant plants. In addition to less lignified cell walls, susceptibility to the pine wood nematode seems associated with the activation of the salicylic acid (SA) defense pathway at 72 hpi, as revealed by the higher SA levels in the tissues of susceptible plants. Cell wall reinforcement and hormone signaling mechanisms seem therefore essential for a resistance response.

Impact of Altitudinal Variation on the Phytochemical Profile, Anthelmintic and Antimicrobial Activity of Two Pinus Species

Active components from natural sources are the current focus in most pharmacological research to provide new therapeutic agents for clinical use. Essential oils from the Pinus species have been traditionally used in medicine. This study aimed to investigate the chemical profile of two Pinus species, Pinus halepensis L. and Pinus pinea Mill, from different altitudes in Libya and study the effect of environmental conditions on the biological activities of essential oils. A clevenger apparatus was used to prepare the essential oils by hydrodistillation. Analyses were done using GC/MS. Anthelmintic and antimicrobial activities were tested against the earthworm Allolobophora caliginosa, gram-positive bacteria, gram-negative bacteria, and fungi. Different chemical profiles were observed among all tested essential oils, and terpenes were the most dominant class. All studied essential oils from the Pinus species exhibited a remarkable anthelmintic activity compared to the standard piperazine citrate drug. Pinus halepensis from both altitudes showed broad-spectrum antimicrobial activity against all tested microorganisms, while Pinus pinea was effective against only Escherichia coli. From these findings, one can conclude that there are variations between studied species. The essential oil compositions are affected by environmental factors, which consequently affect the anthelmintic and antimicrobial activity.

Pinus pinaster Early Hormonal Defence Responses to Pinewood Nematode (Bursaphelenchus xylophilus) Infection

The pinewood nematode (PWN) is the causal agent of pine wilt disease, a pathology that affects conifer forests, mainly Pinus spp. PWN infection can induce the expression of phytohormone-related genes; however, changes at the early phytohormone level have not yet been explored. Phytohormones are low-abundance metabolites, and thus, difficult to quantify. Moreover, most methodologies focus mainly on Arabidopsis or crop species. This work aimed to validate a fast (run time 6.6 min) liquid chromatography-triple quadrupole tandem mass spectrometry (LC-QqQ-MS/MS) analytical method to quantify 14 phytohormones in Pinus pinaster stem tissues. This method was further applied to evaluate, for the first time, early phytohormone changes in susceptible and resistant phenotypes of P. pinaster 24, 48 and 72 h after inoculation (HAI) with PWN. A significant increase in salicylic acid (SA, 48 and 72 HAI) and jasmonic acid methyl ester (JA-ME, 72 HAI) was observed in susceptible phenotypes. Results indicate that the higher susceptibility of P. pinaster to PWN infection might result from an inefficient trigger of hypersensitive responses, with the involvement of JA and SA pathways. This work provides an important update in forest research, and adds to the current knowledge of Pinus spp. defence responses to PWN infection.

Mass spectrometry-based forest tree metabolomics

Research in forest tree species has advanced slowly when compared with other agricultural crops and model organisms, mainly due to the long-life cycles, large genome sizes, and lack of genomic tools. Additionally, trees are complex matrices, and the presence of interferents (e.g., oleoresins and cellulose) challenges the analysis of tree tissues with mass spectrometry (MS)-based analytical platforms. In this review, advances in MS-based forest tree metabolomics are discussed. Given their economic and ecological significance, particular focus is given to Pinus, Quercus, and Eucalyptus forest tree species to better understand their metabolite responses to abiotic and biotic stresses in the current climate change scenario. Furthermore, MS-based metabolomics technologies produce large and complex datasets that require expertize to adequately manage, process, analyze, and store the data in dedicated repositories. To ensure that the full potential of forest tree metabolomics data are translated into new knowledge, these data should comply with the FAIR principles (i.e., Findable, Accessible, Interoperable, and Re-usable). It is essential that adequate standards are implemented to annotate metadata from forest tree metabolomics studies as is already required by many science and governmental agencies and some major scientific publishers. © 2019 John Wiley & Sons Ltd. Mass Spec Rev 40:126-157, 2021.

Effect of Essential Oils on the Release of TNF-α and CCL2 by LPS-Stimulated THP‑1 Cells

Plants and their constituents have been used to treat diverse ailments since time immemorial. Many plants are used in diverse external and internal formulations (infusions, alcoholic extracts, essential oils (EOs), etc.) in the treatment of inflammation-associated diseases, such as those affecting the respiratory tract or causing gastrointestinal or joint problems, among others. To support the traditional uses of plant extracts, EOs have been assessed for their alleged anti-inflammatory properties. However, the effect of EOs on the release of cytokines and chemokines has been much less reported. Considering their traditional use and commercial relevance in Portugal and Angola, this study evaluated the effect of EOs on the in vitro inhibition of the cytokine tumor necrosis factor-α (TNF-α) and the chemokine (C-C motif) ligand 2 (CCL2) by lipopolysaccharide (LPS)-stimulated human acute monocytic leukemia cells (THP-1 cells). Twenty EOs extracted from eighteen species from seven families, namely from Amaranthaceae (Dysphania ambrosioides), Apiaceae (Foeniculum vulgare), Asteraceae (Brachylaena huillensis, Solidago virgaurea), Euphorbiaceae (Spirostachys africana), Lamiaceae (Lavandula luisieri, Mentha cervina, Origanum majorana, Satureja montana, Thymbra capitata, Thymus mastichina, Thymus vulgaris, Thymus zygis subsp. zygis), Myrtaceae (Eucalyptus globulus subsp. maidenii, Eucalyptus radiata, Eucalyptus viminalis) and Pinaceae (Pinus pinaster) were assayed for the release of CCL2 and TNF-α by LPS-stimulated THP-1 cells. B. huillensis, S. africana, S. montana, Th. mastichina and Th. vulgaris EOs showed toxicity to THP-1 cells, at the lowest concentration tested (10 μg/mL), using the tetrazolium dye assay. The most active EOs in reducing TNF-α release by LPS-stimulated THP-1 cells were those of T. capitata (51% inhibition at 20 μg/mL) and L. luisieri (15-23% inhibition at 30 μg/mL and 78-83% inhibition at 90 μg/mL). L. luisieri EO induced a concentration-dependent inhibition of CCL2 release by LPS‑stimulated THP-1 cells (23%, 54% and 82% inhibition at 10, 30 and 90 μg/mL, respectively). These EOs are potentially useful in the management of inflammatory diseases mediated by CCL2 and TNF‑α, such as atherosclerosis and arthritis.

The Effect of Nanocoatings Enriched with Essential Oils on 'Rocha' Pear Long Storage

The effect of coating 'Rocha' pears with alginate-based nanoemulsions enriched with lemongrass essential oil (LG) or citral (Cit) was investigated. Fruit were treated with the nanoemulsions: sodium alginate 2% (w/w) + citral 1% (w/w) (Cit1%); sodium alginate 2% (w/w) + citral 2% (w/w) (Cit2%); sodium alginate 2% (w/w) + lemongrass 1.25% (w/w) (LG1.25%); sodium alginate 2% (w/w) + lemongrass 2.5% (w/w) (LG2.5%). Then, fruit were stored at 0 °C and at 95% relative humidity, for six months. Fruit samples were taken after two, four and six months, and then placed at 22 °C. Upon removal and after 7 d shelf-life, fruit were evaluated for colour CIE (L*, h◦), firmness, soluble solids content (SSC), titratable acidity (TA), weight loss, electrolytic leakage, microbial growth, symptoms of superficial scald and internal browning. All nanoemulsions had droplets in the nano range <500 nm, showed uniformity of particle size and stable dispersion. Cit-nanoemulsions had lower droplet size and higher stability than LG. No nanoemulsion showed cytotoxicity. Coatings reduced fruit colour evolution and preserved better firmness than control. After shelf-life, better firmness was found in LG-coated fruit. Coatings did not affect SSC and TA. Microbial growth was below the safety limits in all treatments. Fruit treated with LG-nanoemulsions did not show scald symptoms and panelists preferred LG1.25% coated fruit. Cit2% treated fruit showed the highest scald and internal browning symptoms, while LG1.25% did not show any disorders. This study suggests that LG-nanocoatings have the potential for preserving the quality of 'Rocha' pear.

Effect of Monochamus galloprovincialis feeding on Pinus pinaster and Pinus pinea, oleoresin and insect volatiles

In Portugal, the pine black sawyer Monochamus galloprovincialis is the principal vector of the pinewood nematode, Bursaphelenchus xylophilus, the causal agent of pine wilt disease (PWD), a lethal phyopathogen with major ecological and economic consequences to European forestry. The aim of this study was to determine the influence of M. galloprovincialis feeding on the volatiles emitted by pine trees. This study focused on the pine species which are most relevant to Portugal, that is, Pinus pinaster (maritime pine) and Pinus pinea (stone or umbrella pine), assessing to what extent pine chemotypes might influence feeding by the insect vector. Preliminary evaluation of each maritime pine essential oil allowed recognizing the existence of two main chemotypes (C1 and C2) and absence of chemical variability in P. pinea. Emission of volatiles from pine trees was evaluated before and during 24 h of feeding by a mixed-sex pair of newly emerged, unfed M. galloprovincialis. Volatiles were also collected from the oleoresin released from the feeding wounds as well as from the insects after feeding. Pine volatiles were collected by solid phase microextraction (SPME) and insect volatiles extracted with pentane, and all analysed by gas chromatography-mass spectrometry (GC-MS) and by GC for component identification and quantification, respectively. Of the seventeen emitted volatiles detected in SPME analyses of P. pinaster, β-pinene, α-pinene, β-caryophyllene, and germacrene D showed the highest average fold increases as a result of M. galloprovincialis feeding. When grouped by P. pinaster chemotype, C1 and C2 groups of trees showed different patterns of responses. β-Caryophyllene and germacrene D showed the highest fold increase in C1 trees, whereas β-pinene and α-pinene clearly dominated in C2 trees. Likewise, the oleoresin volatiles from C1 trees were dominated by δ-3-carene and/or β-pinene, whereas α-pinene and β-pinene were the main volatile components from oleoresin of C2 trees. Nine components were detected in P. pinea volatiles, of which limonene showed the highest fold increase as a result of insect feeding. The volatiles collected from the insects after they had fed on P. pinaster included α-pinene, β-pinene, and abietic acid, and by the straight-chain n-alkanes n-C27, n-C29, and n-C25, together with the methyl-branched hydrocarbons 3-meC29, 2-meC28, and 3-meC27. A better understanding of the responses of different P. pinaster chemotypes to feeding by M. galloprovincialis may be helpful in the development of new lures to improve pine sawyer trapping in integrated pest management for control of PWD.

Experimental Design and Sample Preparation in Forest Tree Metabolomics

Appropriate experimental design and sample preparation are key steps in metabolomics experiments, highly influencing the biological interpretation of the results. The sample preparation workflow for plant metabolomics studies includes several steps before metabolite extraction and analysis. These include the optimization of laboratory procedures, which should be optimized for different plants and tissues. This is particularly the case for trees, whose tissues are complex matrices to work with due to the presence of several interferents, such as oleoresins, cellulose. A good experimental design, tree tissue harvest conditions, and sample preparation are crucial to ensure consistency and reproducibility of the metadata among datasets. In this review, we discuss the main challenges when setting up a forest tree metabolomics experiment for mass spectrometry (MS)-based analysis covering all technical aspects from the biological question formulation and experimental design to sample processing and metabolite extraction and data acquisition. We also highlight the importance of forest tree metadata standardization in metabolomics studies.