Influence of lipids and proteins amounts and pH values on the inhibitory effects of Origanum vulgare L. essential oil against Escherichia coli and Salmonella Typhimurium

Origanum vulgare L. (OVEO) essential oil has been considered a candidate antimicrobial for use in food conservation systems. However, studies on the influence of concomitant variations of different food components or physicochemical parameters on the antibacterial properties of OVEO are scarce. This study assessed the influence of concomitant variations in amounts of proteins - PTN (4.0, 6.0 or 8.0 g/100 mL) and lipids - LIP (3.75, 5.0 or 6.25 g/100 mL) and pH values (5.0, 5.5 or 6.0) in cultivation medium on the inhibitory effects of OVEO against Escherichia coli (EC) and Salmonella Typhimurium (ST). Lowest minimum inhibitory concentration values of OVEO against EC and ST were observed in media with the highest LIP amounts regardless the PTN amount and pH value. In absorbance based microtiter plate assay (MPA), for both EC and ST, OVEO caused the lowest Grmax values in medium containing the highest LIP and PTN amounts and lowest pH value. Highest Grmax values for EC and ST were observed in medium containing the lowest LIP and PTN amount and highest pH value. Grmax values estimated from viable counts of EC and ST in tested media with OVEO confirmed bacterial growth behavior similar to that observed in MPA. Overall, the LIP amount in media was as the most influential factor to enhance the antibacterial effects of OVEO. These results indicate that the concomitant influence of LIP and PTN amounts and pH values on the antibacterial effects of OVEO should be considered for optimizing its antimicrobial efficacy in foods.

Determinação de óleos essenciais de alfavaca (Ocimum gratissimum L. ), orégano (Origanum vulgare L. ) e tomilho (Thymus vulgaris L.) / Determination of essential oils of basil (Ocimum gratissimum L. ), oregano (Ocimum gratissimum L. ) and thyme (Thymus vulgaris L.)

O presente trabalho teve como objetivo a caracterização de plantas frescas e secas (comerciais) de alfavaca, orégano e tomilho, a obtenção dos óleos essenciais através do método de arraste a vapor e a quantificação dos compostos químicos por CG/EM. As plantas frescas e as secas comerciais foram submetidas às análises de umidade, extrato etéreo, proteína, fibra bruta, cinzas, extrato não nitrogenado, valor calórico, teor de óleo essencial e identificação dos compostos majoritários através da cromatografia gasosa-espectrometria de massas. Dentre a caracterização obtida os resultados na base seca mostraram-se promissores, sendo o teor de proteína e de cinzas na alfavaca seca comercial com 17,34 g 100 g-1 e 8,12 g 100 g-1, respectivamente; a fibra bruta no orégano seco comercial com 15,65 g 100 g-1; o extrato etéreo, o extrato não nitrogenado e o valor calórico no tomilho seco comercial com 9,30 g 100 g-1, 52,72 g 100 g-1 e 356,74 Kcal 100 g-1, respectivamente. Obteve-se o maior rendimento de óleo essencial na alfavaca seca comercial com 1,02%, enquanto a alfavaca fresca apresentou o menor rendimento, com apenas 0,13%. Na alfavaca fresca encontrou-se 87,38% de eugenol e 6,27% de timol, enquanto na alfavaca seca comercial observou-se redução no eugenol (71,12%) e aumento do timol (13,28%). No orégano fresco foram quantificados quatro picos o γ-terpineno (33,45%), 4-terpineol (25,59%), timol (14,21%) e carvacrol (2,30%). Já no óleo essencial de orégano seco comercial houve redução no γ-terpineno (28,73%) e aumento no 4-terpineol (27,58%), timol (19,71%) e carvacrol (3,67%). No óleo essencial do tomilho fresco foram quantificados três picos o borneol (66,66%), timol (13,41%) e linalol (3,24%). Por outro lado, no óleo essencial do tomilho seco comercial houve redução no borneol (37,90%) e aumento no timol (20,61%) e linalol (10,34%). Pode-se concluir que as folhas secas comerciais analisadas de alfavaca, orégano, e tomilho apresentam potencial para o enriquecimento dos alimentos ou para a obtenção dos óleos essenciais.

This study aimed to characterize commercial fresh and dry medicinal plants (basil, oregano and thyme), to obtain essential oil by the steam distillation method and to quantify chemical compounds by means of GC/MS. The fresh and dry plants were subjected to the following analyses moisture, ether extract, protein, crude fiber, ash, non-nitrogenous extract, caloric value, essential oil content and identification of major compounds by gas chromatography-mass spectrometry. Considering the obtained characterization, the following results on dry basis proved promising: protein and ash content in commercial dry basil with 17.34 g 100 g-1 and 8.12 g 100 g-1, respectively; crude fiber in commercial dry oregano with 15.65 g 100 g-1; ether extract, non-nitrogenous extract and caloric value in commercial dry thyme with 9.30 g 100 g-1, 52.72 g 100 g-1 and 356.74 Kcal 100 g-1, respectively. The highest essential oil yield was obtained for commercial dry basil with 1.02% and the lowest yield was obtained for fresh basil with only 0.13%. Chromatography indicated 87.38% eugenol and 6.27% thymol in fresh basil. For commercial dry basil, the chromatogram showed a reduction in eugenol (71.12%) and an increase in thymol (13.28%). Four peaks were quantified for fresh oregano the γ-terpinene (33.45%), 4-terpineol (25.59%), thymol (14.21%) and carvacrol (2.30%). For the essential oil of commercial dry oregano, there was a decrease in γ-terpinene (28.73%) and an increase in 4-terpineol (27.58%), thymol (19.71%) and carvacrol (3.67%). In the chromatogram of the essential oil of fresh thyme, three peaks were quantified: borneol (66.66%), thymol (13.41%) and linalool (3.24%). On the other hand, in the chromatogram of the essential oil of commercial dry thyme, there was a decrease in borneol (37.90%) and an increase in thymol (20.61%) and linalool (10.34%). It can be concluded that commercial dry leaves of basil, oregano and thyme are feasible to enrich foods or to obtain essential oils.