Static–dynamic Superheated Liquid Extraction of Phenols from Prosthechea varicosa and Prosthechea karwinskii (orchids) Prior to Determination by LC–DAD

Abstract

Nature has evolved overtime to produce a bewildering diversity of secondary metabolites. Based on empirical observations and folklore, natural product extracts were the first, and for a long time, the only medicines available to mankind. In this research superheated liquid extraction was applied to isolate phenolic compounds from two species of orchids (Prosthechea karwinskii and Prosthechea varicosa). Optimization of the variables influencing the extraction step, (based on sequential static and dynamic modes) for each orchid and each phenolic compound, was performed by multivariate approaches in all instances. Optimization was based on tests for measurement of total phenols (Folin– Ciocalteu assay). The extraction kinetics were studied under the optimal conditions in order to maximize isolation efficiency for each phenol. Separation and quantification of individual compounds were performed by LC–DAD. Representative examples of analytes identified and quantified (phenols) in each orchids were as follows: p–coumaric acid, 31.12 μg/g, and ferulic acid, 26.42 μg/g, for P. karwinskii and o–coumaric acid, 33.11 μg/g, and p–coumaric acid, 27.72 μg/g for P. varicosa. Apigenin and luteolin glucosides, and the phenols tyrosol and vanillin were also detected and quantified. Keywords: Chemistry of natural products, LC–DAD, orchids, phenols, superheated liquid extraction (SLE).