Nitroalkenes and Sesquiterpene Hydrocarbons from the Frontal Gland of Three Prorhinotermes Termite Species

Frontal gland contents of soldiers of three Prorhinotermes species, Prorhinotermes canalifrons, Prorhinotermes inopinatus, and Prorhinotermes simplex, consisted of two groups of compounds: nitroalkenes and sesquiterpene hydrocarbons. Analysis by gas chromatography-mass spectrometry revealed (E)-1-nitropentadec-1-ene as the major component of the glands with mean values of 152, 207, and 293 μg/individual for P. canalifrons, P. inopinatus, and P. simplex, respectively. Four other 1-nitroalkenes (C13, C14, C16, and C17), and two nitrodienes (C15 and C17) were also detected in the three species. The C17:1 nitroalkene was identified as (E)-1-nitroheptadec-1-ene. The sesquiterpene composition of the gland was species-specific: P. simplex contained (3Z,6E)-α-farnesene (mean of 39 μg/individual), while P. canalifrons and P. inopinatus contained the same compound (means of 0.5 and 1.5 μg/individual, respectively) as well as the (3E,6E) isomer (means of 1.8 and 0.7 μg/individual, respectively). Two other sesquiterpenes, trans-β-bergamotene and (Z)-γ-bisabolene, were also found in low quantities in the frontal gland of P. canalifrons.