Calystegine B-4, a novel trehalase inhibitor from Scopolia japonica

GLC-MS analysis has been developed for screening plants of the family Solanaceae for new calystegines. GLC-MS analyses of the extract of Scopolia japonica showed the presence of a new tetrahydroxy-nor-tropane alkaloid in addition to the known calystegines A(3), A(5), B-1, B-2, B-3, and C-1. We gave this new alkaloid the trivial name calystegine B-4. The structure of calystegine B-4 was determined as 1 alpha,2 beta,3 alpha,4 alpha-tetrahydroxy-nor-tropane from a variety of NMR spectral data. Calystegines B-1, B-2, and C-1 are potent competitive inhibitors with K-i values ranging from 10(-6) to 10(-7) M for almond beta-glucosidase, while calystegine B-4 inhibited this enzyme in a competitive manner, with a K-i value of 7.3 mu M Calystegine B-2 is also. potent inhibitor of green coffee bean alpha-galactosidase. whereas calystegine B-4 exhibited no significant activity for this enzyme. Among rat intestinal glycosidases, only trehalase was potently inhibited by calystegine B-4, with an IC50 value of 9.8 mu M. Furthermore, calystegine B-4 potently inhibited pig kidney trehalase in a competitive manner, with a K-i value of 1.2 mu M, but it was almost inactive against yeast and fungal trehalases. (C) 1996 Elsevier Science Ltd.