ABSTRACT
Usnic Acid .................................................................................................. 417 18.3.2 Encapsulation of Usnic Acid in
Poly(Lactic-co-Glycolic Acid) Nanocapsules .......................................................... 417 18.3.2.1 Usnic Acid Loaded Nanocapsules ............................................................. 417 18.3.2.2 Characterization of Usnic Acid Loaded Nanocapsules ............................. 418
18.3.3 Encapsulation of Usnic Acid in Poly(Lactic-co-Glycolic Acid)–Poly (Ethylene Glycol) Blend Microspheres ..................................................................... 418 18.3.3.1 Usnic Acid Loaded Microspheres .............................................................. 418
Of the hundreds of known secondary lichen metabolites, usnic acid is certainly the most extensively studied because it exhibits antimicrobial activity (Correché et al., 1998; Francolini et al., 2004; Lauterwein et al., 1995; Perry et al., 1999; Ribeiro et al., 2006), particularly an antimycobacterial effect (Ingólfsdóttir et al., 1998), and antitumor activity (Pereira et al., 1994; Santos et al., 2005), among other properties. However, the therapeutic use of usnic acid is limited by its very poor water solubility (Kristmundsdóttir, 2005; Kristmundsdóttir et al., 2002) and hepatotoxicity (Favreau et al., 2002; Han et al., 2004; Pramyothin et al., 2004; Ribeiro-Costa et al., 2004; Santos et al., 2006). The use of usnic acid in a safe and ef cient approach therefore requires appropriate nano-or microparticulated systems to increase the therapeutic index of this drug by improving the ef cacy and reducing the toxicity. In this challenging scenario, liposomal and nano-and microparticulated formulations containing usnic acid or usnic acid-β-cyclodextrin inclusion complex were developed and characterized for the in vitro kinetic release, biological activity, and toxicity.
