New Natural Oxygenated Sesquiterpenes and Chemical Composition of Leaf Essential Oil from Ivoirian Isolona dewevrei (De Wild. & T. Durand) Engl. & Diels

Creation of New Oregano Genotypes with Different Terpene Chemotypes via Inter- and Intraspecific Hybridization

Oregano is a medicinal and aromatic plant of value in the pharmaceutical, food, feed additive, and cosmetic industries. Oregano breeding is still in its infancy compared with traditional crops. In this study, we evaluated the phenotypes of 12 oregano genotypes and generated F₁ progenies by hybridization. The density of leaf glandular secretory trichomes and the essential oil yield in the 12 oregano genotypes varied from 97-1017 per cm² and 0.17-1.67%, respectively. These genotypes were divided into four terpene chemotypes: carvacrol-, thymol-, germacrene D/β-caryophyllene-, and linalool/β-ocimene-type. Based on phenotypic data and considering terpene chemotypes as the main breeding goal, six oregano hybrid combinations were performed. Simple sequence repeat (SSR) markers were developed based on unpublished whole-genome sequencing data of Origanum vulgare, and 64 codominant SSR primers were screened on the parents of the six oregano combinations. These codominant primers were used to determine the authenticity of 40 F₁ lines, and 37 true hybrids were identified. These 37 F₁ lines were divided into six terpene chemotypes: sabinene-, β-ocimene-, γ-terpinene-, thymol-, carvacrol-, and p-cymene-type, four of which (sabinene-, β-ocimene-, γ-terpinene-, and p-cymene-type) were novel (i.e., different from the chemotypes of parents). The terpene contents of 18 of the 37 F₁ lines were higher than those of their parents. The above results lay a strong foundation for the creating of new germplasm resources, constructing of genetic linkage map, and mapping quantitative trait loci (QTLs) of key horticultural traits, and provide insights into the mechanism of terpenoid biosynthesis in oregano.

Neuropeltis acuminata (P. Beauv.): Investigation of the Chemical Variability and In Vitro Anti-inflammatory Activity of the Leaf Essential Oil from the Ivorian Species

The variability of chemical composition of the leaf essential oil (EO) from Neuropeltis acuminata, a climbing liana growing wild in Ivory Coast, was investigated for the first time. The in vitro anti-inflammatory activity was also evaluated. Thirty oil samples were isolated from leaves collected in three forests of the country and analyzed using a combination of Column Chromatography (CC), Gas Chromatography with Retention Indices (GC(FID)), Gas Chromatography-Mass Spectrometry (GC-MS), and ¹³Carbon-Nuclear Magnetic Resonance (¹³C-NMR). Fractionation by CC led to the first-time isolation from natural source of δ-cadinen-11-ol, whose structural elucidation by one dimension (1D) and 2D-NMR spectroscopy is reported here. Finally, 103 constituents accounting for 95.7 to 99.6% of the samples’ compositions were identified. As significant variations of the major constituents were observed, the 30 oil compositions were submitted to hierarchical cluster and principal components analyses. Five distinct groups were evidenced: Group I, dominated by (E)-β-caryophyllene, kessane, and δ-cadinene, while the main constituents of Group II were germacrene B, ledol, α-humulene, (E)-γ-bisabolen-12-ol, and γ-elemene. Group III exhibited guaiol, germacrene D, atractylone, (E)-γ-bisabolen-12-ol, δ-cadinene and bulnesol as main compounds. Group IV was dominated by (E)-nerolidol, guaiol, selina-4(15),7(11)-diene and bulnesol, whereas (E)-β-caryophyllene, α-humulene and α-muurolene were the prevalent compounds of Group V. As the harvest took place in the same dry season in the three forests, the observed chemical variability could be related to harvest sites, which includes climatic and pedologic factors, although genetic factors could not be excluded. The leaf oil sample S24 behaved as a high inhibitor of LipOXygenase (LOX) activity (half maximum Inhibitory Concentration, IC₅₀: 0.059 ± 0.001 mg mL⁻¹), suggesting an anti-inflammatory potential.

Chemical Variability and In Vitro Anti-Inflammatory Activity of Leaf Essential Oil from Ivorian Isolona dewevrei (De Wild. & T. Durand) Engl. & Diels

The chemical variability and the in vitro anti-inflammatory activity of the leaf essential oil from Ivorian Isolona dewevrei were investigated for the first time. Forty-seven oil samples were analyzed using a combination of CC, GC(RI), GC-MS and 13C-NMR, thus leading to the identification of 113 constituents (90.8-98.9%). As the main components varied drastically from sample to sample, the 47 oil compositions were submitted to hierarchical cluster and principal components analyses. Three distinct groups, each divided into two subgroups, were evidenced. Subgroup I-A was dominated by (Z)-β-ocimene, β-eudesmol, germacrene D and (E)-β-ocimene, while (10βH)-1β,8β-oxido-cadina-4-ene, santalenone, trans-α-bergamotene and trans-β-bergamotene were the main compounds of Subgroup I-B. The prevalent constituents of Subgroup II-A were germacrene B, (E)-β-caryophyllene, (5αH,10βMe)-6,12-oxido-elema-1,3,6,11(12)-tetraene and γ-elemene. Subgroup II-B displayed germacrene B, germacrene D and (Z)-β-ocimene as the majority compounds. Germacrene D was the most abundant constituent of Group III, followed in Subgroup III-A by (E)-β-caryophyllene, (10βH)-1β,8β-oxido-cadina-4-ene, germacrene D-8-one, and then in Subgroup III-B by (Z)-β-ocimene and (E)-β-ocimene. The observed qualitative and quantitative chemical variability was probably due to combined factors, mostly phenology and season, then harvest site to a lesser extent. The lipoxygenase inhibition by a leaf oil sample was also evaluated. The oil IC50 (0.020 ± 0.005 mg/mL) was slightly higher than the non-competitive lipoxygenase inhibitor NDGA IC50 (0.013 ± 0.003 mg/mL), suggesting a significant in vitro anti-inflammatory potential.

New Natural Oxygenated Sesquiterpenes and Chemical Composition of Leaf Essential Oil from Ivoirian Isolona dewevrei (De Wild. & T. Durand) Engl. & Diels

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.