Leaf essential oil from Ivorian Isolona dewevrei (Annonaceae): Chemical composition and structure elucidation of four new natural sesquiterpenes

Abstract

This work is a contribution to the characterization of aromatic and medicinal plants from Côte d’Ivoire. To date, no phytochemical investigation was reported on Isolona dewevrei. Thus, the aim of this study was to investigate for the first time, the chemical composition of the leaf essential oil from I dewevrei. Two essential oil samples (S1, S2) were analysed by combination of chromatographic [GC(FID) and GC(RI)] and spectroscopic [MS, 13C‐NMR] techniques. As several compounds remained unidentified, particularly in sample S1, this oil was fractionated on silica gel column, leading to the isolation and structural elucidation of four new natural compounds by QTOF‐MS, 1D and 2D‐NMR analyses. These new natural sesquiterpenes were identified as (5αH,10βMe)‐6,12‐oxido‐elema‐1,3,6,11(12)‐tetraene, 6,12‐oxido‐germacra‐1(10),4,6,11(12)‐tetraene, (1βH,5βH)‐6,12‐oxido‐guaia‐6,10(14),11(12)‐trien‐4α‐ol and germacra‐1(10),4,7(11)‐trien‐6,12‐γ‐lactone. Finally, sixty‐eight constituents were identified in both investigated essential oil samples. They accounted for 96.1 and 97.3%, respectively, of the whole chemical composition of S1 and S2. Leaf essential oil from Idewevrei is very rich in sesquiterpenes. Indeed, its majority compounds were germacrene B (20.8 and 24.8%), (5αH,10βMe)‐6,12‐oxido‐elema‐1,3,6,11(12)‐tetraene (10.3 and 0.3%, new compound), germacrene D (7.5 and 17.8%), (Z)‐β‐ocimene (7.8 and 9.7%),γ‐elemene (6.9 and 7.5%) and (E)‐β‐caryophyllene (6.8 and 3.5%). The contents of thermolabile components were assessed by combination of GC(FID) and 13C‐NMR.

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

“…The extraction yields calculated on a weight basis ( w/w ) were in the range of 0.094–0.506%. Analyses were carried out using a combination of GC(RI), GC-MS and 13 C-NMR, following a computerized method developed at the University of Corsica [ 15 , 22 ]. Most of the constituents were identified by the three techniques, including the identification by 13 C-NMR of components present at a content as low as 0.4–0.5% and compiled in our laboratory-made 13 C-NMR spectral data library.…”

“…Special attention was paid to the identification of some compounds. For instance, eight sesquiterpenes previously isolated and characterized from the leaf essential oil of I. dewevrei were identified by their reported 13 C-NMR data and retention indices [ 15 , 16 ]: (5αH,10βMe)-6,12-oxido-elema-1,3,6,11(12)-tetraene (fractions F3 from samples S14 and S47; 48.5 and 39.2%, respectively), 6,12-oxido-germacra-1(10),4,6,11(12)-tetraene (fraction F3 from sample S14; 7.2%), (1βH,5βH)-6,12-oxido-guaia-6,10(14),11(12)-trien-4α-ol (fraction F5 from sample S14; 56.4%), germacra-1(10),4,7(11)-trien-6,12-γ-lactone (fraction F6 from sample S14; 19.3%), (10βH)-1β,8β-oxido-cadina-4-ene (fraction F4 from samples S2, S24 and S44; 34.7, 18.6 and 14.7%, respectively), (7βH)-germacrene D-8α-ol (fraction F5 from sample S24; 29.4%), (7βH)-germacrene D-8β-ol (fraction F5 from sample S24; 9.8%) and cadina-1(10),4-dien-8β-ol (fraction F5 from sample S24; 39.2%). Similarly, germacrene D-8-one previously isolated from the stem bark essential oil of the same species was identified in fraction F3 from sample S24 (28.6%) [ 14 ].…”

“…This was the case for 6,12-oxido-germacra-1(10),4,6,11(12)-tetraene and (5αH,10βMe)-6,12-oxido-elema-1,3,6,11(12)-tetraene, and then germacrene B and γ-elemene. Therefore, their correct contents were obtained by a combination of GC(FID) and 13 C-NMR as previously reported [ 15 , 16 ]. However, δ-elemene and β-elemene were really secondary metabolites produced by the plant and not rearranged products since germacrene A and germacrene C were not detected by 13 C-NMR in the samples.…”

“…The leaf oil studies led to the isolation of seven new sesquiterpenes, characterized as 6,12-oxido-germacra-1(10),4,6,11(12)-tetraene (5αH,10βMe)-6,12-oxido-elema-1,3,6,11(12)-tetraene, germacra-1(10),4,7(11)-trien-6,12-γ-lactone, (1βH,5βH)-6,12-oxido-guaia-6,10(14),11(12)-trien-4α-ol, (10βH)-1β,8β-oxido-cadina-4-ene, (7βH)-germacrene D-8α-ol and (7βH)-germacrene D-8β-ol. NMR data of cadina-1(10),4-dien-8β-ol were also reported for the first time [ 15 , 16 ]. The studied leaf oil samples evidenced three chemical compositions dominated either by germacrene B, (5αH,10βMe)-6,12-oxido-elema-1,3,6,11(12)-tetraene, germacrene D, ( Z )-β-ocimene, γ-elemene and ( E )-β-caryophyllene, or by germacrene D, germacrene D-8-one, (10βH)-1β,8β-oxido-cadina-4-ene, (7βH)-germacrene D-8α-ol and cadina-1(10),4-dien-8β-ol, or by (10βH)-1β,8β-oxido-cadina-4-ene, ( E )-β-caryophyllene, germacrene D, cadina-1(10),4-dien-8β-ol and caryophyllene oxide.…”

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

“…In previous works, we investigated and reported for the first time the chemical compositions of leaf, root and stem bark essential oils from I. dewevrei, dominated by germacrene B/germacrene D and by cyperene, respectively. From the leaf oil, four new compounds were isolated and characterized as 6,12-oxido-germacra-1(10),4,6,11 (12)-tetraene, (5αH,10βMe)-6,12-oxido-elema-1,3,6,11 (12)-tetraene, germacra-1(10),4,7(11)-trien-6,12-γ-lactone and (1βH,5βH)-6,12-oxido-guaia-6,10(14),11 (12)-trien-4α-ol [8]. The structure of germacrene D-8-one, another new natural compound, was also elucidated after isolation from the stem bark essential oil of the plant [9].…”