Composition, Mosquito Larvicidal, Biting Deterrent and Antifungal Activity of Essential Oils of Different Plant Parts of Cupressus arizonica var. glabra (‘Carolina Sapphire’)

Abstract

Essential oils obtained by hydrodistillation of female cones (FC), male cones (MC), needle-twigs (NT) and wood-bark (WB) of ‘Carolina Sapphire’ [Cupressus arizonica var glabra (Sudw.) Little] were analyzed simultaneously by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). The main constituents of the investigated essential oils were as follows: FC: α-pinene 68.5% and myrcene 11.9%; MC: α-pinene 22.5%, epi- zonarene 9.9%, zonarene 6.9%, limonene 6.8% and cadina-3,5-diene 6.1%; NT: α-pinene 20.7%, epi-zonarene 10.4%, zonarene 7.6%, limonene 5.9% umbellulone 5.8% and cadina-3,5-diene 5.8%; WB: α-pinene 40.7%, limonene 3.2% and umbellulone 2.9%. Essential oils were evaluated for antifungal activity against the strawberry anthracnose causing fungal plant pathogens Colletotrichum acutatum, C. fragariae and C. gloeosporioides. Only WB essential oil showed moderate activity when compared with the commercial antifungal standards. Carolina Sapphire essential oils exhibited biting deterrent activity at 10 pg/cm2 with Biting Deterrence Index (BDI) values of 0.64, 0.59, 0.65 and 0.72, for FC, MC, NT and WB, respectively, and were significantly lower (P≤0.05) than the synthetic insect repellent, DEET (N,N-diethyl-meta-toluamide), at 25 nmol/cm2 against Aedes aegypti. The biting deterrence of NT and WB oils at 100 μg/cm2 with BDI values of 1.04 and 1.01, respectively, were similar, whereas the activity of MC (BDI=0.88) and FC (BDI=0.62) essential oils was lower than DEET at 25 nmol/cm2. Essential oil from FC with LD50 of 33.7 ppm was most toxic against 1-day-old Ae. aegypti larvae at 24-h post treatment. Female cone essential oil was significantly more toxic than MC (LD50=53.6 ppm), NT (LD50=55.5 ppm) and WB (LD50=44.6 ppm) essential oils.