Antimicrobial activity and chemical composition of the essential oil of Hofmeisteria schaffneri.

OBJECTIVES: The aims of this study were to establish the antimicrobial potential of Hofmeisteria schaffneri essential oil and its chemical composition. METHODS: The essential oils of Hofmeisteria schaffneri harvested at flowering (batches I and IV) and non-flowering (batches II and III) seasons were prepared by hydrodistillation and analysed by GC and GC-MS. The aqueous and organic (CH(2) Cl(2) -MeOH 1 : 1) extracts were prepared by using infusion and maceration techniques, respectively. The in-vitro antimicrobial activity of the preparations and compounds against Candida albicans and some bacteria (Gram-negative and Gram-positive) was assessed using the broth dilution method in 96-microplate wells. KEY FINDINGS: Forty-four compounds, representing ∼90% of the total constituents, were identified in the essential oil of Hofmeisteria schaffneri collected in flowering (batches I and IV) and non-flowering (batches II and III) seasons. In all cases, several thymol analogues were the major components of the oils (∼65%); some small differences in the relative proportions of these constituents were observed. The infusion exhibited an antibacterial activity against Staphylococcus aureus and Bacillus subtilis, with a MIC value of 64 µg/ml in each case. The essential oil batches were active against Staphylococcus aureus, with MIC ranging from 48 to 192 µg/ml. They were, however, inactive against Gram-negative bacteria, including Pseudomonas aeruginosa, Escherichia coli and Salmonella typhi (MIC > 1024 µg/ml). On the other hand, the infusion of the plant as well as the oil from batch I displayed anti-Candida albicans activity, with MIC of 128 and 192 µg/ml, respectively. Finally, the organic extract did not displayed significant activity against the tested microorganisms (MIC ≥ 1024 µg/ml). Some of the compounds isolated from the plant were also tested. Compounds 8 and 38, which were present in the essential oils, displayed the best antibacterial effect against Gram-positive bacteria (MIC ranging between 32 and 64 µg/ml). Compounds 6 (present in the infusion) and 10 (present in all preparations) showed higher activity against the yeast (MIC = 128 µg/ml) than the remaining compounds, with MIC values ranging from 256 to 512 µg/ml. CONCLUSIONS: The composition and antimicrobial activity of the oils changed slightly from flowering to non-flowering seasons. The results of the present investigation provide in-vitro scientific support for the use of the plant against skin infections in Mexican folk medicine.

Enzymatic hydrolysis of fructans in the tequila production process.

In contrast to the hydrolysis of reserve carbohydrates in most plant-derived alcoholic beverage processes carried out with enzymes, agave fructans in tequila production have traditionally been transformed to fermentable sugars through acid thermal hydrolysis. Experiments at the bench scale demonstrated that the extraction and hydrolysis of agave fructans can be carried out continuously using commercial inulinases in a countercurrent extraction process with shredded agave fibers. Difficulties in the temperature control of large extraction diffusers did not allow the scaling up of this procedure. Nevertheless, batch enzymatic hydrolysis of agave extracts obtained in diffusers operating at 60 and 90 degrees C was studied at the laboratory and industrial levels. The effects of the enzymatic process on some tequila congeners were studied, demonstrating that although a short thermal treatment is essential for the development of tequila's organoleptic characteristics, the fructan hydrolysis can be performed with enzymes without major modifications in the flavor or aroma, as determined by a plant sensory panel and corroborated by the analysis of tequila congeners.

Determination of terpenes in tequila by solid phase microextraction-gas chromatography-mass spectrometry.

Solid phase microextraction and capillary gas chromatography-mass spectrometry were used for the determination of seven terpenes in tequila. The method was selected based on the following parameters: coating selection (PA, PDMS, CW/DVB, and PDMS/DVB), extraction temperature, addition of salt, and extraction time profile. The extraction conditions were: PDMS/DVB fiber, Headspace, 100% NaCl, 25 degrees C extraction temperature, 30 min extraction time and stirring at 1200 rpm. The calibration curves (50-1000 ng/ml) for the terpenes followed linear relationships with correlation coefficients (r) greater than 0.99, except for trans,trans-farnesol (r = 0.98). RSD values were smaller than 10% confirmed that the technique was precise. Samples from 18 different trade brands of "Aged" tequila analyzed with the developed method showed the same terpenes in different concentrations. The analytical procedure used is selective, robust (more than 100 analyses with the same fiber), fast and of low-cost.

Characterization of three agave species by gas chromatography and solid-phase microextraction-gas chromatography-mass spectrometry.

Steam distillation (SD) extraction-solid-phase microextraction coupled to GC-MS was developed for the determination of terpenes and Bligh-Dyer extraction-derivatization coupled with GC for the determination of fatty acids such as ethyl esters were used. It was found that the three different Agave species have the same profile of fatty acids; the quantity of these compounds is different in each Agave variety. On the other hand, different terpenes were identified in the three Agave plants studied: nine in A. salmiana, eight in A. angustifolia and 32 in A. tequilana Weber var. azul.