Chemical Compositions of Essential Oils from German, Roman, and Chinese Chamomile Flowers and Their Biological Activities against Three Economically Important Insect Pests

In this study, the essential oils (EOs) of flowers from German chamomile (GCEOs 1-5) Matricaria chamomilla L., Roman chamomile (RCEOs 1-2) Chamaemelum nobile (L.) All, and Chinese chamomile (CCEO-1) or "Juhua" Chrysanthemum morifolium Ramat were characterized by GC-FID and GC-MS analysis. EOs were tested for biting deterrence/repellency against Aedes aegypti and hybrid imported fire ants and for toxicity against Anastrepha suspensa. GCEOs 1-5 were characterized by the higher contents of alpha-bisabolol oxide A (43%-66%) and alpha-bisabolol oxide B (10%-16%) whereas isobutyl angelate (16%-17%), 2-butenyl angelate (12%-13%), isoamyl tiglate (11%-12%), 3-methyl pentylangelate (8%-11%), and trans-pinocarveol (6%-7%) were major compounds of RCEOs 1 and 2. The CCEO-1 was rich in borneol (31%), ar-curcumene (12%), bornyl acetate (7%) and intermedeol (5%). Biting deterrence of GCEO-2 and-3, and CCEO-1 was similar to N,N-diethyl-3-methylbenzamide (DEET) whereas the activity of the other EOs was lower than DEET against Ae. aegypti. The activity of pure compounds alpha bisabolol and 1,6-dioxaspiro[4.4]non-3-en-2-one from German chamomiles was also similar to DEET against Ae. aegypti. Repellency of German chamomile EO, GCEO-F against hybrid imported fire ants was higher whereas the activity of Roman chamomile EO, RCEO-PT was lower than DEET. All EOs, GCEO-4, RCEO-2, and CCEO-1 were toxic against female A. suspensa. Further research using intensive in vivo bioassays will be conducted to explore the potential of these natural products in insect pest management strategies.