Hypericum sp.: essential oil composition and biological activities

Phytochemical composition of Hypericum genus has been investigated for many years. In the recent past, studies on the essential oils (EO) of this genus have been progressing and many of them have reported interesting biological activities. Variations in the EO composition of Hypericum species influenced by seasonal variation, geographic distribution, phenological cycle and type of the organ in which EO are produced and/or accumulated have also been reported. Although many reviews attributed to the characterization as well as biological activities of H. perforatum crude extracts have been published, no review has been published on the EO composition and biological activities of Hypericum species until recently (Crockett in Nat Prod Commun 5(9):1493–1506, 2010; Bertoli et al. in Global Sci Books 5:29–47, 2011). In this article, we summarize and update information regarding the composition and biological activities of Hypericum species EO. Based on experimental work carried out in our laboratory we also mention possible biotechnology approaches envisaging EO improvement of some species of the genus.Fundação para a Ciência e a Tecnologia (FCT) - project PTDC/AGR AAM/70418/2006, SFRH/BD/ 13283/2003

Facile and smart synthesis of benzyl salicylate via vapor-phase transesterification over monoliths coated with zirconia and its modified versions

1257-1269Al(III)/ZrO2 catalysts with Al(III) content ranging from 5–25 wt% have been coated on honeycomb monoliths by dip & dry technique. These catalysts have also been prepared in their powder form. All the prepared catalysts have been characterized by surface acidity, crystallinity, functionality and morphology. The catalytic activity of Al(III)/ZrO2 has been determined in vapor-phase as well as liquid-phase transesterification of methyl salicylate with benzyl alcohol. The honeycomb form of the catalysts shows almost a 1.4 fold time increase in the catalytic activity when compared to the powder forms. Further, the effect of calcination temperature on the activity has also been discussed. The effect of poisoning of acid sites by adsorbed pyridine (base) and its effect on the surface acidity has been correlated with PXRD phases along with catalytic activity. Catalytic recyclability of Al(III)/ZrO2 catalysts has also been measured

Simple but efficient synthesis of novel substituted benzimidazoles over ZrO₂-Al₂O₃

<p>Solid-acid catalytic materials such as ZrO₂-Al₂O₃ containing 80 mol% of ZrO₂ were prepared by the solution combustion method (SCM) using different fuels such as urea, hexamethylene tetramine, glycine, and sucrose. All the prepared solid acid catalytic materials were characterized for their physico-chemical properties like crystalinity, acidity, functionality and morphology. These materials were evaluated for their catalytic activity in the synthesis of a series of novel substituted benzimidazoles. The reaction conditions were optimized by varying the solvents, reaction temperature, weight of solid acid catalyst, molar ratio of the reactants, and reaction time. The ZrO₂-Al₂O₃ solid acid catalytic material prepared by urea as a fuel was found to be highly active, recyclable, and reusable in the synthesis of benzimidazoles. A possible reaction mechanism for the synthesis of benzimidazoles is also proposed.</p