Browsing by Author "Gasques Rocha Pinheiro, Beatriz"

Geometric isomers are of extreme importance due to the different properties of E and Z compounds. The interconversion between these forms allow to explore a vast amount of applications since their use in perfume and food industry until the development of photoactive drugs and advanced polymers. Included in this scenario are the E/Z isomers of pepper alkaloids, whose broad range of desirable pharmacological activities, such as anti-inflammatory, antioxidant and anti-cancer effects, makes them a focus in multidisciplinary research. Black pepper contains several of these alkaloids, among which piperine is the most abundant. Its properties have been studied for many years, with highlight for its pungency and flavour, in addition to medicinal applications that date from the development of ancient Indian and Chinese medicine. Piperine and structure-related compounds undergo rapid double bond isomerization in the presence of light, equilibrating to a mixture of four geometrical isomers, due to the two conjugated double bonds present in their structures. The biological activity of these isomers differs from those of the natural abundant E/E molecules. Thus, emphasizing the importance of having reliable analytical assays for their separation, detection and quantification. The current project pursued the development of a robust HPLC assays for isomers separation for piperine and some analogues. The effort included the extraction of piperine from black pepper and its use for the synthesis of highly pure piperylin and piperlonguminine standards. Piperine extraction kinetics was also studied to optimize the extraction procedure. The standards of alkaloids were isomerized using sunlight and then HPLC separation methods on chiral stationary phases were successfully established to resolve their E/Z isomers. Isocratic runs were also developed for piperine, piperylin and piperlonguminine, with the goal of adapting these methods to LC/MS application in the future. These last separations could be accomplished within 25 minutes with critical resolutions values larger than 1.8.