Enteric-Coated Cycloastragenol Capsules: Enhanced Drug Stability and Oral Bioavailability

Cycloastragenol (CAG) is a secondary metabolite isolated from Radix Astragali. Present in all known Astragalus spp., CAG (Fig. 1) is both a triterpene aglycone and the most common genuine aglycone in the bioactive triterpenoid saponins called astragalosides (ASTs) (Rios and Waterman, 1997). Although CAG and the ASTs are found in all tissues of the Astragalus shrubs, the highest concentrations are localized in the roots (Yu et al., 2007b). Ten out of the eleven ASTs found in the root of A. membranaceus contain CAG as the aglycone, including AST IV, the primary characteristic and main bioactive AST present in the roots of this species (Kitagawa et al., 1983; McKenna et al., 2002; Sevimli-Gur et al., 2011; Verotta and El-Sebakhy, 2001; Yu et al., 2007a; Zhou et al., 2012). CAG, AST IV, and other related molecules isolated from Astragalus spp. have also been identified as small-molecule telomerase activators, substances that can induce the elongation of telomeres, the protective DNA sequences at the terminal ends of chromosomes (de Jesus et al., 2011; Fauce et al., 2008; Harley et al., 2011; Yang et al., 2012; Yung et al., 2012; Zhou et al., 2012).