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This study aimed to investigate the chemical composition of the leaf essential oil from Ivoirian Isolona dewevrei. A combination of chromatographic and spectroscopic techniques (GC(RI), GC-MS and 13C-NMR) was used to analyze two oil samples (S1 and S2). Detailed analysis by repetitive column chromatography (CC) of essential oil sample S2 was performed, leading to the isolation of four compounds. Their structures were elucidated by QTOF-MS, 1D and 2D-NMR as (10βH)-1β,8β-oxido-cadin-4-ene (38), 4-methylene-(7αH)-germacra-1(10),5-dien-8β-ol (cis-germacrene D-8-ol) (52), 4-methylene-(7αH)-germacra-1(10),5-dien-8α-ol (trans-germacrene D-8-ol) (53) and cadina-1(10),4-dien-8β-ol (56). Compounds 38, 52 and 53 are new, whereas NMR data of 56 are reported for the first time. Lastly, 57 constituents accounting for 95.5% (S1) and 97.1% (S2) of the whole compositions were identified. Samples S1 and S2 were dominated by germacrene D (23.6 and 20.5%, respectively), followed by germacrene D-8-one (8.9 and 8.7%), (10βH)-1β,8β-oxido-cadin-4-ene (7.3 and 8.7), 4-methylene-(7αH)-germacra-1(10),5-dien-8β-ol (7.8 and 7.4%) and cadina-1(10),4-dien-8β-ol (7.6 and 7.2%). Leaves from I. dewevrei produced sesquiterpene-rich essential oil with an original chemical composition, involving various compounds reported for the first time among the main components. Integrated analysis by GC(RI), GC-MS and 13C-NMR appeared fruitful for the knowledge of such a complex essential oil.

The volatile components of the leaves of five Bursera species, B. copallifera, B. exselsa, B. mirandae, B. ruticola and B. fagaroides var. purpusii were determined by gas chromatography–mass spectrometry (GC–MS). Germacrene D was one of the predominant components (15.1–56.2%) of all of these species. Germacrene D has also been found in other Bursera species and some species of Commiphora, the sister group of Bursera, suggesting that the production of germacrene D might be an ancient trait in the genus Bursera.

Germacrene D, a sesquiterpenoid compound found mainly in plant essential oils at a low level as (+) and/or (−) enantiomeric forms, is an ingredient for the fragrance industry, but a process for the sustainable supply of enantiopure germacrene D is not yet established. Here, we demonstrate metabolic engineering in yeast ( Saccharomyces cerevisiae ) achieving biosynthesis of enantiopure germacrene D at a high titer. To boost farnesyl pyrophosphate (FPP) flux for high-level germacrene D biosynthesis, a background yeast chassis (CENses5C) was developed by genomic integration of the expression cassettes for eight ergosterol pathway enzymes that sequentially converted acetyl-CoA to FPP and by replacing squalene synthase promoter with a copper-repressible promoter, which restricted FPP flux to the competing pathway. Galactose-induced expression of codon-optimized plant germacrene D synthases led to 13–30 fold higher titers of (+) or (−)-germacrene D in CENses5C than the parent strain CEN.PK2.1C. Furthermore, genomic integration of germacrene D synthases in GAL80 , LPP1 and rDNA loci generated CENses8(+D) and CENses8(−D) strains, which produced 41.36 µg/ml and 728.87 µg/ml of (+) and (−)-germacrene D, respectively, without galactose supplementation. Moreover, coupling of mitochondrial citrate pool to the cytosolic acetyl-CoA, by expressing a codon-optimized ATP-citrate lyase of oleaginous yeast, resulted in 137.71 µg/ml and 815.81 µg/ml of (+) or (−)-germacrene D in CENses8(+D)* and CENses8(−D)* strains, which were 67–120 fold higher titers than in CEN.PK2.1C. In fed-batch fermentation, CENses8(+D)* and CENses8(−D)* produced 290.28 µg/ml and 2519.46 µg/ml (+) and (−)-germacrene D, respectively, the highest titers in shake-flask fermentation achieved so far. Key points • Engineered S. cerevisiae produced enantiopure (+) and (−)-germacrene D at high titers • Engineered strain produced up to 120-fold higher germacrene D than the parental strain • Highest titers of enantiopure (+) and (−)-germacrene D achieved so far in shake-flask

Background The sesquiterpene germacrene D is a highly promising product due to its wide variety of insecticidal activities and ability to serve as a precursor for many other sesquiterpenes. Biosynthesis of high value compounds through genome mining for synthases and metabolic engineering of microbial factories, especially Saccharomyces cerevisiae , has been proven to be an effective strategy. However, there have been no studies on the de novo synthesis of germacrene D from carbon sources in microbes. Hence, the construction of the S. cerevisiae cell factory to achieve high production of germacrene D is highly desirable. Results We identified five putative sesquiterpene synthases (AcTPS1 to AcTPS5) from Acremonium chrysogenum and the major product of AcTPS1 characterized by in vivo, in vitro reaction and NMR detection was revealed to be (–)-germacrene D. After systematically comparing twenty-one germacrene D synthases, AcTPS1 was found to generate the highest amount of (–)-germacrene D and was integrated into the terpene precursor-enhancing yeast strain, achieving 376.2 mg/L of (–)-germacrene D. Iterative engineering was performed to improve the production of (–)-germacrene D, including increasing the copy numbers of AcTPS1 , tHMG1 and ERG20 , and downregulating or knocking out other inhibitory factors (such as erg9 , rox1 , dpp1 ). Finally, the optimal strain LSc81 achieved 1.94 g/L (–)-germacrene D in shake-flask fermentation and 7.9 g/L (–)-germacrene D in a 5-L bioreactor, which is the highest reported (–)-germacrene D titer achieved to date. Conclusion We successfully achieved high production of (–)-germacrene D in S. cerevisiae through terpene synthase mining and metabolic engineering, providing an impressive example of microbial overproduction of high-value compounds.

Specificity of olfactory receptor neurones plays an important role in food and host preferences of a species, and may have become conserved or changed in the evolution of polyphagy and oligophagy. We have identified a major type of plant odour receptor neurones responding to the sesquiterpene germacrene D in three species of heliothine moths, the polyphagous Heliothis virescens and Helicoverpa armigera and the oligophagous Helicoverpa assulta. The neurones respond with high sensitivity and selectivity to (-)-germacrene D, as demonstrated by screening via gas chromatography with numerous mixtures of plant volatiles. Germacrene D was present in both host and non-host plants, but only in half of the tested species. The specificity of the neurones was similar in the three species, as shown by the \"secondary\" responses to a few other sesquiterpenes. The effect of (-)-germacrene D was about ten times stronger than that of the (+)-enantiomer, which again was about ten times stronger than that of (-)-alpha-ylangene. Weaker effects were obtained for (+)-beta-ylangene, (+)-alpha-copaene, beta-copaene and two unidentified sesquiterpenes. The structure-activity relationship shows that the important properties of (-)-germacrene D in activating the neurones are the ten-membered ring system and the three double bonds acting as electron-rich centres, in addition to the direction of the isopropyl-group responsible for the different effects of the germacrene D enantiomers.

Eryngium dilatatum Lam. is a thorny Iberian Peninsula endemic species belonging to the Apiaceae family that has not been previously analysed from a chemical point of view. Following our studies on this genus, we characterized the chemical composition of the essential oils from the different parts (inflorescences, stems + leaves, and roots) of this species; these parts were gathered in Cádiz (Spain). The specimens were collected in July during the flowering period and air-dried before the oil extraction by hydro-distillation. The essential oils were analysed by gas chromatography and gas chromatography coupled with mass spectrometry. The different parts of the plant yielded low amounts of pale yellow oil, with the roots being the fraction that provided the lowest amount of oil. The chemical characterization of the essential oils showed qualitative and quantitative differences between the fractions examined, but all of them showed the same principal compound, germacrene D (9.1–46.5%). Similarly, all the fractions shared most of their representative constituents, with their percentage compositions being different from one sample to the other: α-cadinol (3.8%), bicyclogermacrene (3.5%), octanal (3.1%), and spathulenol (2.5%) were found in the inflorescences; octanal (8.1%), α-cadinol (3.7%), δ-cadinene (3.6%), (E)-caryophyllene (2.6%), bicyclogermacrene (2.5%), and spathulenol (2.4%) were found in the stems and leaves; and spathulenol (4.6%), α-cadinol (4.4%), khusinol (3.2%), α-muurolol (3.1%), and δ-cadinene (2.6%) were found in the roots. As far as we know, this is the first report about the chemical composition of this endemic species of the Iberian Peninsula. It contributes to the knowledge of this species and to the genus to which it belongs. This species could be considered as a natural source of germacrene D, which is a sesquiterpene hydrocarbon with active properties.

Essential oil from the leaves of Artemisia vulgaris L. (Compositae) cultivated in Brazil was investigated for its chemical composition and biological activities including antibacterial, antifungal, and anthelmintic. The constituents of essential oils isolated by hydro-distillation were examined by GC-MS and a total of 18 components were identified. The essential oil was dominated by oxygenated sesquiterpenes (44.4%), sesquiterpene hydrocarbons (33.3%), and oxygenated monoterpenes (16.6%). Caryophyllene (37.45%), germacrene D (16.17%), and humulene (13.66%) were the major components. The essential oils from A. vulgaris showed bactericidal and fungicidal properties against Staphylococcus aureus and Candida albicans, respectively. Anthelmintic activity against Haemonchus contortus was absent in this essential oil. Altogether above results indicate that essential oils from A. vulgaris can be used for various medicinal purposes.

Hedyosmum purpurascens is an endemic species found in the Andes of Ecuador and it is characterized by its pleasant smell. In this study, essential oil (EO) from H. purpurascens was obtained by the hydro-distillation method with a Clevenger-type apparatus. The identification of the chemical composition was carried out by GC–MS and GC–FID in two capillary columns, DB-5ms and HP-INNOWax. A total of 90 compounds were identified, representing more than 98% of the total chemical composition. Germacrene-D, ϒ-terpinene, α-phellandrene, sabinene, O-cymene, 1,8-cineole and α-pinene accounted for more than 59% of the EO composition. The enantioselective analysis of the EO revealed the occurrence of (+)-α-pinene as a pure enantiomer; in addition, four pairs of enantiomers were found (α-phellandrene, o-cymene, limonene and myrcene). The biological activity against microbiological strains and antioxidants and the anticholinesterase properties were also evaluated and the EO showed a moderate anticholinesterase and antioxidant effect, with an IC50 value of 95.62 ± 1.03 µg/mL and a SC50 value of 56.38 ± 1.96. A poor antimicrobial effect was observed for all the strains, with MIC values over 1000 µg/mL. Based on our results, the H. purpurasens EO presented remarkable antioxidant and AChE activities. Despite these promising results, further research seems essential to validate the safety of this medicinal species as a function of dose and time. Experimental studies on the mechanisms of action are essential to validate its pharmacological properties.

Cacao (Theobroma cacao L.) is a crop of globally importance on whose production around 20 million people depend directly. The crop is threatened due to the incidence of diseases caused by phytopathogenic fungi such as Moniliophthora roreri, causing losses of more than 80 % of the annual production. For this reason, in this study, a natural product such as the essential oil (EO) obtained from Siparuna guianensis was evaluated as a control alternative. The chemical composition of the EO, as well as the antifungal effect in vitro and in vivo on M. roreri, the causal agent of moniliasis frosty pod rot, were determined in the cacao pods located in a commercial plantation in southern Huila, Colombia. 28 compounds were detected, predominating: D-Germacrene (26.5 %), (E)-nerolidol (21.5 %), β-caryophyllene (9.3 %), elemol (8.0 %), bicyclogermacrene (7.5 %), δ-elemene (3.5 %), β-elemene (3.0 %), and α-pineno (2.4 %). At a concentration of 1000 μg ml-1 of EO in vitro, an inhibitory effect of 98 % on the mycelial growth of M. roreri was obtained. In the in vivo test at concentrations of 1000 μg ml-1 and 750 μg ml-1, a direct relationship in the decrease of the incidence, external gravity, and internal gravity of M. roreri in cocoa pods was observed, using EO as fungicide. It was concluded that S. guianensis EO represents a great potential for the control of frosty pod rot.

This study investigated optimal supplemental multispectral light-emitting diode (LED) conditions for the growth and essential oil accumulation of Ocimum gratissimum L. (OG) cultivated in a net house over 15 weeks. We hypothesized that supplemental lighting could increase biomass while affecting oil yield or vice versa. Nine lighting treatments were established, combining red (R) and blue (B) with ultraviolet-A (UV-A), green (G), or far-red (Fr) lights, applied for 4, 6, or 8 h/night at 80–120 µmol·m−2·s−1. Essential oils were analyzed by GC/MS-FID, revealing 21–28 compounds, dominated by phenylpropanoids (59.4–71.2%). Eugenol (58.5–69.8%), (Z)-β-ocimene (10.2–12.1%), and germacrene D (7.6–12.1%) were the major constituents. The oils showed weak antimicrobial activity against Candida albicans. All lighting treatments significantly enhanced fresh biomass and oil yield (p < 0.001) compared with the control. The optimal treatment (F2; R, B, and UV-A lights at a photon flux ratio of 71:20:9; 100 µmol·m−2·s−1, 6 h/night) yielded the highest fresh biomass (13.07 ± 0.71 Mg/ha), essential oil (31.39 ± 1.71 L/ha), and eugenol (21.09 ± 1.15 L/ha). These findings demonstrate the strong influence of spectral composition and exposure duration on OG productivity and highlight the potential of tailored LED strategies to improve both biomass and oil quality in cultivation systems.