A comparative study of sequential and simultaneous enzymatic and ultrasound-assisted aqueous two-phase extraction for anticholesterol compounds from Strobilanthes crispus leaves.

An innovative ultrasonic-assisted enzymatic aqueous two-phase extraction (UAE-ATPE) method was applied to enhance the yield from Strobilanthes crispus leaves, exploring both sequential and simultaneous approaches. Comparative analysis included assessing total phenolic content (TPC), total flavonoid content (TFC), partition coefficient (k) and recovery (R). Liquid chromatography-mass spectrometry and scanning electron microscopy evaluated extracts from both techniques. Simultaneous UAE-ATPE demonstrated significantly higher TPC (5.7±0.1 mg GAE/g dry leaves) and TFC (3.3±0.1 mg QE/g dry leaves) compared to sequential extraction, where TPC and TFC measured 4.5±0.3 mg GAE/g dry leaves and 1.7±0.1 mg QE/g dry leaves. Additionally, simultaneous UAE-ATPE yielded higher k and R values for phenolic and flavonoid compounds. Notably, it identified 32.4% of the area corresponding to 6 compounds, surpassing the 25.3% area identified sequentially with 13 compounds. A collaborative effect of enzymatic hydrolysis and ultrasonic extraction was observed in simultaneous UAE-ATPE. In the inhibition test on the HMG-CoA reductase enzyme, simultaneous UAE-ATPE extract (200 µg/mL) exhibited exceptional results, achieving superior inhibition of 66.1% compared to the sequential method's inhibition of 39.4%. This underscores the efficacy of simultaneous UAE-ATPE in producing concentrated anti-cholesterol compounds. The study strongly emphasizes the superiority of simultaneous UAE-ATPE over the sequential approach.

Kinetic modelling of the oxidation of large aliphatic hydrocarbons using an automatic mechanism generation.

A mechanism generator code to automatically generate mechanisms for the oxidation of large hydrocarbons has been successfully modified and considerably expanded in this work. The modification was through (1) improvement of the existing rules such as cyclic-ether reactions and aldehyde reactions, (2) inclusion of some additional rules to the code, such as ketone reactions, hydroperoxy cyclic-ether formations and additional reactions of alkenes, (3) inclusion of small oxygenates, produced by the code but not included in the handwritten C(1)-C(4) sub-mechanism yet, to the handwritten C(1)-C(4) sub-mechanism. In order to evaluate mechanisms generated by the code, simulations of observed results in different experimental environments have been carried out. Experimentally derived and numerically predicted ignition delays of n-heptane-air and n-decane-air mixtures in high-pressure shock tubes in a wide range of temperatures, pressures and equivalence ratios agree very well. Concentration profiles of the main products and intermediates of n-heptane and n-decane oxidation in jet-stirred reactors at a wide range of temperatures and equivalence ratios are generally well reproduced. In addition, the ignition delay times of different normal alkanes was numerically studied.