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 α,2β,3α,4α-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 β-glucosidase, while calystegine B 4 inhibited this enzyme in a competitive manner, with a K i value of 7.3 μM. Calystegine B 2 is also a potent inhibitor of green coffee bean α-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 IC 5 0 value of 9.8 μM. Furthermore, calystegine B 4 potently inhibited pig kidney trehalase in a competitive manner, with a K i value of 1.2 μM, but it was almost inactive against yeast and fungal trehalases.