Chemical composition, antimicrobial and larvicidal activities of essential oils of two Syzygium species from Vietnam.

The present study is the first to investigate the chemical composition, antimicrobial and larvicidal activities of the essential oils from the leaves of Syzygium attopeuense (Gagnep.) Merr. & L.M.Perry and Syzygium tonkinense (Gagnep.) Merr. & L.M.Perry collected in Vietnam. The essential oils were extracted by hydrodistillation and analyzed by GC and GC-MS. The study indicated the presence of a high percentage of sesquiterpenes in both investigated essential oils. The major components of S. attopeuense essential oil were bicyclogermacrene (24.26%), (E)-caryophyllene (11.72%), and (E)-ß-ocimene (6.75%), whereas S. tonkinense essential oil was dominated by (E)-caryophyllene (80.80%). The antimicrobial activity of essential oils was evaluated by broth microdilution assay to determine the minimum inhibitory concentration (MIC) and median inhibitory concentration (IC50). Both essential oils exhibited remarkable inhibitory activity against all tested Gram-positive bacteria and yeast than Gram-negative bacteria. Among them, essential oils of S. attopeuense and S. tonkinense possessed the strongest activity against Enterococcus faecalis (MIC = 4.00 µg/mL; IC50 = 1.69 µg/mL) and Candida albicans (MIC = 16.00 µg/mL; IC50 = 8.67 µg/mL), respectively. Furthermore, the larvicidal activity of essential oils was tested using fourth-instar larvae of Aedes aegypti. Results from the larvicidal test revealed that both essential oils had an excellent inhibitory effect against A. aegypti larvae with LC50 values from 25.55 to 30.18 µg/mL and LC90 values from 33.00 to 39.01 µg/mL. Our findings demonstrate that the essential oil extracted from S. attopeuense and S. tonkinense are potential sources of natural antimicrobials and can act as inexpensive mosquito larvicidal agents.

An erratic parasitism found in the lungs of sheep during experimental infection with Fasciola gigantica (Japanese strain).

An erratic parasitism was observed in the lungs of sheep experimentally infected with Fasciola gigantica at autopsy 14 weeks after inoculation. Macroscopically, several hyperaemia of 7.5-12.5 mm in diameter were found on the surface of the lungs. Juvenile flukes detected in the lungs were much smaller than those in the liver of the same sheep. A slight inflammatory reaction was observed in the lungs and it is likely that the flukes had migrated in the pleural cavity for some time. Occasionally, a mixed thrombus with many eosinophils was found in the blood vessels adjacent to the bronchia, although no cough was observed clinically. This suggests that diagnosis of juvenile fluke is difficult not only by parasitological but also serological methods.