New compounds from the essential oil of Vetiveria nigritana roots from Mali

Essential oil from roots (2% w/w) of Vetiveria nigritana (Benth.) Stapf (Poaceae) from Mali was analysed by GC–MS. Among the components, four new compounds were isolated from the oil and identified by combination of EI–MS and NMR data; they were two norsesquiterpene hydrocarbons, 9,9‐dimethyl‐8‐methylenetricyclo[5.2.2.03,7]undec‐3‐ene (dehydronigritene 1) and 8,9,9‐trimethyltricyclo[5.2.2.03,7]undec‐3‐ene (nigritene 2), and two sesquiterpene acids : 2,6,6‐trimethyltricyclo[5.3.1.01,5]undec‐8‐ene‐8‐carboxylic acid (cedren‐15‐oic acid 3) and 6,6‐dimethyl‐7‐methylenetricyclo[6.2.1.01,5]undecane‐2‐carboxylic acid (2‐epi‐prezizanoic acid 4). The percentages in oil of compounds 1, 2, 3 and 4 were 0.9%, 2.2%, 7.5% and 15%, respectively, of the total amount of components.