Tilia species have been used as anxiolytics for many years. In a previous study anxiolytic-like effects of a hexane extract of Tilia americana var. mexicana inflorescences were observed in experimental models in mice. To get additional insights into the neuroactive actions of this particular Tilia species, in this study we report a bioactivity guided-fractionation of the extract and separation by column chromatographic methods to isolate three fatty acids and a triterpene identified as beta-sitosterol as major constituents. Our results revealed that the crude extract at 10 and 30 mg/kg I. P. and some pooled fractions at the same dosages potentiated sodium pentobarbital-induced sleeping time and caused a significant increase in the time spent at the open-arm sides in the plus-maze test. A reduction in the exploratory behavioral pattern manifested as ambulatory activity, as well as head dipping and rearing tests was also observed. Further fractionation and purification yielded four major fractions containing fatty acids and beta-sitosterol as the active compounds. A dose-response curve of beta-sitosterol in the range 1 to 30 mg/kg doses indicated that this compound produced an anxiolytic-like action from 1 to 10 mg/kg and a sedative response when the dose was increased to 30 mg/kg, these effects resemble those produced by diazepam (0.1 mg/kg). Our results suggest that hexane extract of Tilia americana var. mexicana produces depressant actions on the central nervous system, at least in part, because of the presence of beta-sitosterol and some fatty acids that remain to be identified.

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A model for a system of a finite number of molecules in confinement is presented and expressions for determining the temperature, pressure, and volume of the system are derived. The present model is a generalisation of the Zwanzig-Langevin model because it includes pressure effects in the system. It also has general validity, preserves the ergodic hypothesis, and provides a formal framework for previous studies of hydrogen clusters in confinement. The application of the model is illustrated by an investigation of a set of prebiotic compounds exposed to varying pressure and temperature. The simulations performed within the model involve the use of a combination of molecular dynamics and density functional theory methods implemented on a computer system with a mixed CPU-GPU architecture.

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