Formation of Nitrogen-Containing Metabolites from the Main Iridoids of Harpagophytum procumbens and H. zeyheri by Human Intestinal Bacteria - Baghdikian, Béatrice; Guiraud-Dauriac, Hélene; Ollivier, Evelyne; N'Guyen, Annie; Dumenil, Gérard; Balansard, Guy (Planta Medica, 1999)