ABSTRACT
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 GCMS. 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.
O presente estudo é o primeiro a investigar a composição química, as atividades antimicrobiana e larvicida dos óleos essenciais das folhas de Syzygium attopeuense (Gagnep.) Merr. & L.M.Perry e Syzygium tonkinense (Gagnep.) Merr. & L.M.Perry coletadas no Vietnã. Os óleos essenciais foram extraídos por hidrodestilação e analisados por GC e GCMS. O estudo indicou a presença de alta porcentagem de sesquiterpenos em ambos os óleos essenciais investigados. Os principais componentes do óleo essencial de S. attopeuense foram biciclogermacreno (24,26%), (E)-cariofileno (11,72%) e (E)-ß-ocimeno (6,75%), enquanto o óleo essencial de S. tonkinense foi dominado por (E)-cariofileno (80,80%). A atividade antimicrobiana dos óleos essenciais foi avaliada pelo ensaio de microdiluição em caldo para determinar a concentração inibitória mínima (CIM) e a concentração inibitória mediana (IC50). Ambos os óleos essenciais exibiram notável atividade inibitória contra todas as bactérias Gram-positivas e leveduras testadas do que bactérias Gram-negativas. Entre eles, os óleos essenciais de S. attopeuense e S. tonkinense possuíam a atividade mais forte contra Enterococcus faecalis (CIM = 4,00 µg/mL; IC50 = 1,69 µg/mL) e Candida albicans (CIM = 16,00 µg/ml; IC50 = 8,67 µg/ml), respectivamente. Além disso, a atividade larvicida de óleos essenciais foi testada usando larvas de quarto instar de Aedes aegypti. Os resultados do teste larvicida revelaram que ambos os óleos essenciais tiveram um excelente efeito inibitório contra larvas de A. aegypti com valores de CL50 de 25,55 a 30,18 µg/ml e valores de CL90 de 33,00 a 39,01 µg/ml. Nossos achados demonstram que o óleo essencial extraído de S. attopeuense e S. tonkinense são fontes potenciais de antimicrobianos naturais e podem atuar como agentes larvicidas baratos para mosquitos.
Subject(s)
Oils, Volatile , Syzygium , Larvicides , Anti-Infective Agents , VietnamABSTRACT
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.