Biol. Pharm. Bull. 28(11) 2035—2039 (2005)

cose is replaced by a carbon atom, have been extensively studied during the last three decades. It has been shown that the conformation of C-glucosides is significantly different from that of O-glucosides. C-Glucosides are stable to enzymatic as well as acidic degradation, which is why they have potential as hydrolytically stable O-glucoside analogs for enzyme inhibitors. The microflora in the human intestinal tract plays important roles in the metabolism of many substances. C-Glucosyl bonds of various C-glucosides including mangiferin, abrusin 2 -O-b-D-apioside, aloeresin A, aloesin, barbaloin, bergenin, homoorientin, puerarin, and safflor yellow B are also transformed to the corresponding aglycone by human intestinal bacteria. Most research has been focused on the synthesis of C-glucosides. Naturally-occurring C-glucosides, however, have advantages and pharmacological activities different from their aglycones. However, to date, there is little information concerning the cleavage mechanism of C-glucosides by enzymes. Mangiferin (2-b-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone), a xanthone C-glucoside from Mangifera indica L. (Anacardiaceae), can be used for the study of C-glucosyl-cleaving. In studies in vivo, mangiferin has been reported to have many biological activities, including antitumor, antidiabetic, antioxidant, hepatoprotective, and immunomodulative activities, whereas its aglycone shows anti-inflammatory, vasorelaxation, and antiplatelet activities. The specific bacterium involved in the C-glucosylcleaving of mangiferin was isolated and classified as Bacteroides sp. MANG. Our previous study has shown that the mangiferin C-glucosyl-cleaving enzyme is an inducible enzyme produced by Bacteroides sp. MANG. The enzyme can break the C–C linkage in mangiferin to give norathyriol as an aglycone and seems to be different from O-glucosidases. The main objective of the present research was to study the C-glucosyl-cleaving activity at the enzymatic level. This paper describes the factors associated with the C-glucosylcleaving activity and purification of C-glucosyl-cleaving enzyme.