Microcalorimetric determination of the activity of supercritical extracts of wormwood (Artemisia absinthium L.) over Spodoptera littoralis

The aim of this study is to develop a method and to determine by means of isothermal microcalorimetry the activity of supercritical extracts obtained from growth-controlled wormwood (Artemisia absinthium L.) over Spodoptera littoralis L. (S. littoralis), a polyphagous pest of the Mediterranean crops. In order to achieve this goal, a three-step microcalorimetric method has been developed to insure the quality of the measurements and the validity of the results. Once optimized, different extracts of wormwood obtained by means of supercritical fluid extraction and by traditional methods have been used to investigate their effects over S. littoralis. The microcalorimetric method serves as a tool to complement other bioassays found in the literature. Several extracts from supercritical extractions with solvent density ranging from 485.5 to 819.5 kg m^?3 have been tested. The influence of an entrainer addition to the supercritical fluid has also been investigated. The traditional extracts were obtained by hydrodistillation and organic Soxhlet extraction. The supercritical extracts were more efficient against S. littoralis than the traditionally obtained extracts.     

Integral equation formulation for buoyancy-driven convection problems

An integral equation formulation for buoyancy-driven convection problems is developed and illustrated. Buoyancy-driven convection in a bounded cylindrical geometry with a free surface is studied for a range of aspect ratios and Nusselt numbers. The critical Rayleigh number, the nature of the cellular motion, and the heat transfer enhancement are computed using linear theory. Green's functions are used to convert the linear problem into linear Fredholm integral equations. Theorems are proved which establish the properties of the eigenvalues and eigenfunctions of the linear integral operator which appears in these equations.     

Composition and antioxidant activity of Thymus vulgaris volatiles: Comparison between supercritical fluid extraction and hydrodistillation

Supercritical fluid extraction (SFE) of the volatile oil from Thymus vulgaris L. aerial flowering parts was performed under different conditions of pressure, temperature, mean particle size and CO₂ flow rate and the correspondent yield and composition were compared with those of the essential oil isolated by hydrodistillation (HD). Both the oils were analyzed by GC and GC‐MS and 52 components were identified. The main volatile components obtained were p‐cymene (10.0–42.6% for SFE and 28.9–34.8% for HD), γ‐terpinene (0.8–6.9% for SFE and 5.1–7.0% for HD), linalool (2.3–5.3% for SFE and 2.8–3.1% for HD), thymol (19.5–40.8% for SFE and 35.4–41.6% for HD), and carvacrol (1.4–3.1% for SFE and 2.6–3.1% for HD). The main difference was found to be the relative percentage of thymoquinone (not found in the essential oil) and carvacryl methyl ether (1.0–1.2% for HD versus t?0.4 for SFE) which can explain the higher antioxidant activity, assessed by Rancimat test, of the SFE volatiles when compared with HD. Thymoquinone is considered a strong antioxidant compound.     

Excess volumes and excess viscosities of binary mixtures of cyclic ethers with bromobenzene

From density and viscosity measurements at 25 and 40°C, excess volumes and excess viscosities of the binary mixtures of a cyclic ether with bromobenzene were determined. The results are correlated by means of a Redlich-Kister type equation and interpreted in terms of molecular interactions.     

Permanently oriented antibody immobilization for digoxin determination with a flow-through fluoroimmunosensor

This paper reports a new flow-through fluoroimmunosensor, the function of which is based on antibodies immobilized on an inmunoreactor of controlled-pore glass (CPG), for determination of digoxin, used in the treatment of congestive heart failure and artery disease. The immunosensor has a detection limit of 1.20 microg L(-1) and provides high reproducibility (RSD=4.5% for a concentration of 0.0025 mg L(-1), and RSD=6.7% for 0.01 mg L(-1)). The optimum working concentration range was found to be 1.2 x 10(-3)-4.0 x 10(-2) mg L(-1). The lifetime of the immunosensor was about 50 immunoassays; if stored unused its lifetime can be extended to three months. A sample speed of about 10-12 samples per hour can be attained. Possible interference from substances with structures similar to digoxin (morphine, heroin, tebaine, codeine, pentazocine and narcotine) was investigated. No cross-reactivity was seen at the highest digoxin: interferent ratio studied (1:100). The proposed fluoroimmunosensor was successfully used to determine digoxin concentrations in human serum samples.     

Enrichment of the thymoquinone content in volatile oil from Satureja montana using supercritical fluid extraction

Supercritical fluid extraction (SFE) of the volatile oil from Satureja montana L. was performed under different conditions of pressure (90 and 100 bar), temperature (40 and 50°C), mean particle sizes (0.4, 0.6 and 0.8 mm) and CO₂ flow rate (0.8, 1.1 and 1.3 kg/h) to understand the influence of these parameters on the composition and yield of this oil. The results were compared with those obtained for the essential oil isolated by hydrodistillation (HD). The volatile and the essential oil were analysed by GC and GC‐MS. The main compounds are carvacrol (52.2–62.0% for HD vs. 41.7–64.5% for SFE), thymol (8.6–11.0% for HD vs. 6.0–11.3% for SFE), p‐cymene (6.9–12.8% for HD vs. 6.0–17.8% for SFE), γ‐terpinene (6.4–9.4% for HD vs. 2.3–6.0% for SFE) and β‐bisabolene (2.0–2.7% for HD vs. 2.2–3.5% for SFE). The major difference between SFE and HD was the relative amount of thymoquinone, an oxygenated monoterpene with important biological activities, which can be ten‐fold higher in volatile oil (1.6–3.0 for SFE vs. 0.2% for HD). The morphology of the glandular trichomes of S. montana and the effect of the grinding process on them was also evaluated by SEM.     

Supercritical fluid extraction of the volatile oil from Santolina chamaecyparissus

Supercritical fluid extraction (SFE) of the volatile oil from Santolina chamaecyparissus L. flower heads was performed under different conditions of pressure, temperature, mean particle size and CO₂ flow rate. This oil was compared with the essential oil isolated by hydrodistillation (HD). The SFE volatile and essential oils were analysed by GC and GC‐MS. The range of the main volatile components obtained with HD and SFE were, respectively: 1,8‐cineole (25–30% and 7–48%), camphor (7–9% and 8–14%), borneol (7–8% and 2–11%), terpinen‐4‐ol (6–7% and 1–4%), terpinolene (1–4% and 1–7%) and isobornyl acetate (1–2% and 1–11%). The chemical composition of the extracts was greatly influenced by the conditions of pressure and temperature used. In fact, it was possible to enrich the sesquiterpene fraction by increasing the pressure from 8 to 9 MPa, while changing the temperature from 40 to 50°C at 90 bar enriched of the volatiles in n‐alkanes.