ABSTRACT
Plants synthesize many classes of organic chemical compounds ranging from simple structures to complex molecules as part of their normal metabolic processes. These compounds are broadly characterized as (a) primary metabolites which encompass substances such as nucleic acids, proteins, lipids, and polysaccharides that are the fundamental, biologically active chemical units of living plant cells, and (b) secondary metabolites which typically have larger, more complex chemical architectures that incorporate one or more primary metabolites into their structures. Various types of secondary metabolites synthesized by plants are commonly referred to as phytochemicals and include carotenoids, phenolics, alkaloids, terpenes, sterols, saponins, nitrogen-containing compounds, and organosulfur compounds (Liu, 2004). The most studied of the phytochemicals are the phenolics and carotenoids. Phenolics are compounds possessing one or more aromatic rings with one or more hydroxyl groups and generally are categorized as phenolic acids, avonoids, stilbenes, coumarins, tannins, isoavones, and
CONTENTS
6.1 Introduction ................................................................................................ 177 6.2 PLPW Extraction Process .......................................................................... 178
6.2.1 Basic Concepts ................................................................................ 178 6.2.2 Equipment ....................................................................................... 180
6.3 Applications of PLPW Extraction ............................................................ 184 6.3.1 Effect of the Extraction Temperature and Pressure .................. 187 6.3.2 Fractionation of Compounds of Different Polarity ................... 190
6.4 Modeling of PLPW Extraction of Bioactives from Plant Materials ......193 6.5 Conclusions ................................................................................................. 195 References ............................................................................................................. 196
lignans. The avonoids are further classied as avonols, avones, avanols (catechins), avanones, and anthocyanins.
