In Vitro Permeation of Mesembrine Alkaloids from Sceletium tortuosum across Porcine Buccal, Sublingual, and Intestinal Mucosa - Shikanga, Emmanuel A.; Hamman, Josias H.; Chen, Weiyang; Combrinck, Sandra; Gericke, Nigel; Viljoen, Alvaro M. (Planta Medica, 2012)