Analysis of pentaterpenoids

Abstract

Triterpenes are the most representative group of phytochemicals as over 30,000 of such compounds are recognized to exist (Muffler et al., 2011). They are composed of six C5 isoprene units (Alqahtani et al., 2013) and are biosynthesized via the cyclization of squalene (Oldfield and Lin, 2012), a C30 hydrocarbon which is considered to be the simplest triterpene vis-a`-vis the complexity of its carbon skeleton (Catchpole et al., 1997). Triterpenes can be classified according to the number of cyclic structures making up such compounds. Once considered biologically inactive, there is now an increased research interest in pentacyclic triterpenes (also known as pentaterpenoids), which are secondary metabolites that have recently been found to possess a broad range of pharmacological actions ( Jager et al., 2009; Peng et al., 2014), as it will be discussed later on. Pentacyclic triterpenes can be further classified into the oleanane, ursane, lupine, and hopane groups (Hill and Connolly, 2011), which can occur as free triterpenoids or triterpenic glycosides (Dzubak et al., 2006). Before going further, one must be aware that although the terms “triterpenes” and “triterpenoids” are often used interchangeably to refer to the same C30-terpene compounds, this is not exact. This is because while the term “triterpene” actually describes naturally occurring terpenes, the term “terpenoid” also refers to natural degradation products such as terpene alcohols, aldehydes, and hydrogenation products (Eggersdofer, 2005).