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, 13 C‐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 13 C‐NMR.