Synthesis of α-Corocalene
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K. Ngo, K. Cheung and G. D. Brown, J. Chem. Res. (S), 1998, 80 DOI: 10.1039/A705069KKeywords:
Pulegone
Monoterpene
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Pulegone
Monoterpene
Terpene
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Twenty-six glucoconjugated monoterpene indole alkaloids, including 12 new compounds, rhynchophyllosides A–L (1–12), and 14 known ones, 13–26, were obtained from the hook-bearing stems of Uncaria rhynchophylla (Miq.) Miq. ex Havil. Their structures were unambiguously elucidated by analyses of UV, MS, NMR, ECD, and single-crystal X-ray diffraction data. The ESI-MSn behavior of the new glucoalkaloids was also elucidated. Although comprising the same glucosyl moiety, the aglycone skeletons and glucosidic numbers and linkage varied greatly, implying the diversity in biosynthetic pathways. This is the first report of such structurally diverse glucoconjugated monoterpene indole alkaloids from U. rhynchophylla. Compound 1 represents a new subtype of oxindole alkaloid with a seven-membered D-ring, 10 is a rare monoterpene indole alkaloid with the glucosyl moiety located at C-9, 4 and 5 are the first two oxindole alkaloid diglycosides, and 11 and 12 represent the first two examples of alkaloids with a quinolone nucleus from the genus Uncaria. Compound 10 exhibited moderate acetylcholinesterase (AChE) inhibitory activity with an IC50 value of 10.5 μM. Molecular docking was performed to explore the binding mode of inhibitor 10 at the active site of AChE.
Monoterpene
Indole alkaloid
Moiety
Oxindole
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Abstract The essential oil of Minthostachys spicata (Benth.) Epl. was obtained by hydrodistillation from aerial parts of the plant in a 0.53% yield related to the dry weight. The composition of the oil was analysed by gas chromatography and gas chromatography‐mass spectrometry. The oil was found to contain 54.7% oxygenated monoterpenes, the major compounds being menthone (14.5%), 2‐hydroxy‐ p ‐menth‐1‐en‐3‐one (12.5%) and pulegone (9.7%). Spathulenol (4.9%) was the principal oxygenated sesquiterpene. There were few monoterpene hydrocarbons (3.2%) with limonene as the main component of this fraction. β‐Caryophyllene (4.9%) and viridiflorene (3.5%) were the most abundant sesquiterpene hydrocarbons.
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Monoterpene
Menthone
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Abstract Rotundifolone, a monoterpene isolated from the essential oil of the leaves of Mentha x villosa, is a constituent of several essential oils and known to have spasmolytic activity. The present study aimed to investigate the correlation between structure and spasmolytic activity of rotundifolone and its analogues in ileum isolated from guinea-pig. Five of the seven tested analogues were found to have a spasmolytic effect more potent than rotundifolone itself, except for pulegone and (+)-limonene. The comparison between rotundifolone and limonene oxide showed that the absence of the keto group did not decrease the relaxant effect. Comparison of the spasmolytic activity between rotundifolone and (+)-pulegone showed that the absence of the epoxy group did not decrease the relaxation of the ileum. Carvone epoxide was found to be significantly more potent than rotundifolone. The monoterpene (-)-carvone produced ileum relaxation and was more potent than its enantiomer (+)-carvone. (+)-Limonene and pulegone oxide showed a similar effect. The study showed that the functional groups and their position at the ring of rotundifolone contributed to the relaxation activity of the ileum. The absence of the oxygenated molecular structure is not a critical requirement for the molecule to be bioactive.
Pulegone
Monoterpene
Carvone
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Pulegone
Monoterpene
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Monoterpene
Pulegone
Mentha arvensis
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The composition of the essential oils of Bystropogon plumosus, B. origanifolius var. palmensis, B. wildpretii, B. maderensis, and B. canariensis var. smithianus were studied by GLC and GLC/MS. The first four species provide relatively similar oils characterized by monoterpene ketones as the main constituents while the last species is quite different with main constituents consisting of mono- and sesquiterpene hydrocarbons. In B. plumosus the ontogenetic variation of the monoterpene ketones was studied for a period of four years. During this time the behaviour of pulegone was inversely correlated with that of menthone and isomenthone. Pulegone was the most active compound of the monoterpene ketones in antimicrobial tests using three species of bacteria and fungi, respectively.
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Monoterpene
Menthone
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Pelargonium graveolens is a wild predecessor to rose-scented geranium hybrids prized for their essential oils used as fragrances and flavorings. However, little is known about their biosynthesis. Here we present metabolic evidence that at least two distinct monoterpene biosynthetic pathways contribute to their volatile profiles, namely, cyclic p-menthanes such as (-)-isomenthone and acyclic monoterpene alcohols such as geraniol and (-)-citronellol and their derivatives (referred to here as citronelloid monoterpenes). We established their common origin via the 2C-methyl-d-erythritol-4-phosphate pathway but found no indication these pathways share common intermediates beyond geranyl diphosphate. Untargeted volatile profiling of 22 seed-grown P. graveolens lines demonstrated distinct chemotypes that preferentially accumulate (-)-isomenthone, geraniol, or (-)-citronellol along with approximately 85 minor volatile products. Whole plant 13CO2 isotopic labeling performed under physiological conditions permitted us to measure the in vivo rates of monoterpenoid accumulation in these lines and quantify differences in metabolic modes between chemotypes. We further determined that p-menthane monoterpenoids in Pelargonium are likely synthesized from (+)-limonene via (+)-piperitone rather than (+)-pulegone. Exploitation of this natural population enabled a detailed dissection of the relative rates of competing p-menthane and citronelloid pathways in this species, providing real time rates of monoterpene accumulation in glandular trichomes.
Monoterpene
Pulegone
Citronellol
Chemotype
Carvone
Terpene
Pelargonium
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Monoterpene
Pulegone
Terpene
Carvone
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Essential oil content and composition of the leaves of Bystropogon plumosus (L. fil.) L'Her. (Lamiaceae) have been analyzed by GLC/MS, GLC, TLC, 13C-NMR of the entire oil and polarimetry of the main compounds. These are the monoterpene ketones (+)-pulegone, (+)-isomenthone, (-)-menthone, (rac)-piperitone and piperitenone as well as (-)-limonene and (+)-linalool, representing more than 85% of the components. A relatively high yield of volatiles (> 1 ml per 100 g fr. w.) was obtained.
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Monoterpene
Menthone
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