Extraction and evaluation of antimicrobial activities of essential oils from orange peel cultivada no município de Can Tho, Vietnã

This study determined the extraction conditions, chemical composition, and antimicrobial activities of the essential oils of Citrus nobilis. The results illustrated that soaking in the 9% (w/v) NaCl solution for 2 h with a sample and solvent ratio of 1:3 (w/v) and a subsequent extraction time of 45 min yielded the highest extraction efficiency, reaching 3.66% (w/w). The main chemical components of the essential oils were limonene (90.42%), [beta]-myrcene (4.7%), and [alpha]-pinene (1.22%). The minimum inhibitory concentration (MIC) at the density of 5*[10.sup.4], 5*[10.sup.5], and 5*[10.sup.6] cells/mL of Escherichia coli were 100, 125, and 125 mg/mL, respectively; for Staphylococcus aureus were 75, 100, and 125 mg/mL, respectively; and for Bacillus cereus were 50, 75, and 100 mg/mL, respectively. The minimum bactericidal concentration (MBC) at densities of 5*[10.sup.4], 5*[10.sup.5], 5*[10.sup.6] cells/mL of E. coli were 175, 225, 225 mg/mL, S. aureus were 150, 200, 225 mg/mL, and B. cereus were 125, 175, 200 mg/mL, respectively. The inhibitory activities of Aspergillus flavus of orange essential oils according to the agar dilution method at concentrations of 0.025-0.1%) on the 5th day were 8.84-30.61%. Key words: antibacterial, antifungal, Citrus nobilis, essential oils, extraction conditions, orange peel. Este estudo teve como objetivo determinar as condições de extração, composição química e atividades antimicrobianas dos óleos essenciais de Citrus nobilis. Os resultados demonstram que a imersão na solução de NaCl a 9% (p/v) por 2 h com uma proporção de amostra e solvente de 1:3 (p/v) e um tempo de extração subsequente de 45 min produziu a maior eficiência de extração, atingindo 3,66 % (p/p). Os principais componentes químicos dos óleos essenciais foram limoneno (90,42%), [beta]-mirceno (4,7%) e [alpha]-pineno (1,22%). A concentração inibitória mínima (CIM) na densidade de 5*[10.sup.4], 5*[10.sup.5] e 5*[10.sup.6] células/mL de Escherichia coli foram 100, 125 e 125 mg/mL, respectivamente, e para Staphylococcus aureus foram 75, 100 e 125 mg/mL, respectivamente, e para Bacillus cereus foram 50, 75 e 100 mg/mL, respectivamente. A concentração bactericida mínima (MBC) em densidades de 5*[10.sup.4], 5*[10.sup.5], 5*[10.sup.6] células/mL de E. coli foram 175, 225, 225 mg/mL, S. aureus foram 150, 200, 225 mg/mL e B. cereus foram 125, 175, 200 mg/mL, respectivamente. As atividades inibitórias de Aspergillus flavus dos óleos essenciais de laranja, de acordo com