Factors affecting the phase behavior and antimicrobial activity of carvacrol microemulsions.

The aim of this study was to investigate some factors that can contribute to the formulation of aqueous-based carvacrol microemulsion that can potentially be used in food preservation or disinfection. For this purpose the capacity of formation of carvacrol microemulsion was first revealed by studying the phase behavior of that compound in five different non-ionic microemulsion systems. Factors affecting that phase behavior like the type of non-ionic surfactant and presence of solubilization enhancers were also studied. The fully dilutable microemulsion system that can incorporate high carvacrol amount, as revealed from the phase diagrams, was chosen for the antibacterial evaluation study. The same microemulsion system was re-formulated in a cationic form by substituting the non-ionic surfactant, Tween 20 (T20) with the cationic cetylpyridinium chloride (CPC). The disc diffusion method was used to evaluate the activity of these microemulsion systems against different pathogenic bacteria. Results of the phase behavior study showed that carvacrol is a challenging phenolic compound which did not lend itself easily for solubilization in a fully dilutable non-ionic microemulsion. Incorporation of some solubilization enhancers like propylene glycol (PG) or short chain alcohols can fulfill this purpose however high surfactant/carvacrol ratio (9:1) was still required to solubilize only 1.0 wt% carvacrol in dilutable microemulsion. The antibacterial evaluation study at that concentration revealed that non-ionic carvacrol microemulsion formulated with T20 and a solubilization enhancer did not exhibit better antimicrobial activity than the same concentration of carvacrol formulated in surfactant-free aqueous solution composed of water/PG (1:1). On the other hand, the CPC-formulated carvacrol microemulsion showed significantly higher antibacterial activity than T20-formulated microemulsion. Results of the current investigation shed the light on the solubilization capacity and phase behavior of carvacrol in non-ionic microemulsion and the potential of using cationic carvacrol microemulsion in disinfection and decontamination applications.

Analysis and antibacterial activity of Nigella sativa essential oil formulated in microemulsion system.

The Essential oil (EO) of Nigella sativa (black cumin) was extracted from the crude oil and the volatile constituents were characterized using gas chromatographic analysis. The EO was formulated in water-based microemulsion system and its antibacterial activity against six pathogenic bacteria was evaluated using the agar well diffusion method. This activity was compared with two other well known biologically active natural and synthetic antimicrobials namely eugenol and Ceftriaxone(®). Results showed that N. sativa EO microemulsion was highly effective against S. aureus, B. cereus and S. typhimurium even at the lowest tested concentration of that EO in the microemulsion (100.0 µg/well). Interestingly, the EO microemulsion showed higher antibacterial activity than Ceftriaxone solution against S. typhimurium at 400.0 µg/well and almost comparable activity against E. coli at 500.0 µg/well. No activity was detected for the EO microemulsion against L. monocytogenes and P. aeruginosa. Eugenol which was also formulated in microemulsion was less effective than N. sativa EO microemulsion except against P. aeruginosa. The synthetic antibiotic (Ceftriaxone) was effective against most of the six tested bacterial strains. This work is the first report revealing the formulation of N. sativa EO in microemulsion system and investigating its antibacterial activity. The results may offer potential application of that water-based microemulsion in controlling the prevalence of some pathogenic bacteria.

Chemical compositions and antioxidant/antimicrobial activities of various samples prepared from Schinus terebinthifolius leaves cultivated in Egypt.

Essential oil, dichloromethane extract, and ethanol extract were prepared from fresh Schinus terebinthifolius leaves cultivated in Egypt. The essential oil was analyzed by gas chromatography and gas chromatography/mass spectrometry. The essential oil comprised 4.97% monoterpenes, 56.96% sesquiterpenes, 34.37% oxygenated monoterpenes, and 3.32% oxygenated sesquiterpenes. The major compounds in the essential oil were cis-beta-terpineol (GC peak area%, 17.87%), (E)-caryophyllene (17.56%), beta-cedrene (9.76%), and citronellal (7.03%). The major phenolic compounds identified in the ethanol extract were caffeic acid (5.07 mg/100 mg extract), coumaric acid (1.64 mg), and syringic acid (1.59 mg). The antioxidant activity of ethanol extract, which was comparable with that of butylhydroquinone, was superior to essential oil and dichloromethane extract in 2,2-diphenylpicrylhydrazyl and beta-carotene/bleaching assays. The dichloromethane extract exhibited the greatest antimicrobial activity against 6 strains, followed by the ethanol extract and the essential oil.

Chemical composition of volatile extract and biological activities of volatile and less-volatile extracts of juniper berry (Juniperus drupacea L.) fruit.

Volatile chemicals in a dichloromethane extract from a steam distillate of juniper berry fruit (Juniperus drupacea L.) and its two column chromatographic fractions (eluted with hexane and ethyl ether) were analyzed by gas chromatography/mass spectrometry. The major compounds in the dichloromethane extract were alpha-pinene (23.73%), thymol methyl ether (17.32%), and camphor (10.12%). A fraction eluted with hexane contained alpha-pinene (44.24%) as the major constituent. A fraction eluted with ethyl ether had thymol methyl ether (22.27%) and camphor (19.65%) as the main components. Three samples prepared from the distillate and two additional samples prepared by petroleum ether and ethanol extraction directly from juniper berry fruits exhibited clear antioxidant activities with dose response in both 1,2-diphenyl picrylhydrazyl and beta-carotene assays. All samples except the hexane fraction showed comparable activities to that of the synthetic antioxidant t-butyl hydroquinone at a level of 200 microg/mL in the two testing systems. The extracts of dichloromethane, petroleum ether, and ethanol exhibited appreciable antimicrobial activities against six microorganisms with minimum inhibitory concentrations ranging from 0.5 mg/mL (volatile extract against Candida albicans ) to 1.2 mg/mL (ethanol extract against Aspergillus niger ). The results of the present study suggest that this fruit could be a natural antioxidant supplement for foods and beverages.