The Japanese honey locust, Gleditsia japonica Miquel (Fabaceae; Japanese name: saikachi) grows in Japan, Korea, and China. The dried fruits have been used as a diuretic and an expectorant in traditional oriental medicine. The cotyledon of the seed of <I>G. japonica</I> contains rare N³-prenylated purine alkaloid glucosides, such as locustoside A and saikachinoside A. Larvae of the wild bruchid seed beetle Bruchidius dorsalis infest the seeds. In the course of our investigation on biologically active compounds concerned in the relationship between the seed-eating larvae of the bruchid beetle and the host plant, we isolated three new compounds, designated saikachinoside A monosulfate (1), saikachinoside A disulfate (2), and locustoside B disulfate (3), from the water extract of the pupal case built by the larvae of B. dorsalis. The negative ion mode HRESIFTMS of 1 indicated the presence of a sulfur atom in 1 and a molecular formula of C₁₆H₂₃N₅O₁₀S. The MS/MS fragment ion at m/z 396 [M–H–80]^– suggested the presence of a sulfate group, which was supported by the observation of an IR absorption band at 1258 cm^–1. The UV spectrum of 1 implied the presence of a 3,7-disubstituted isoguanine skeleton. The 1D and 2D NMR spectra of 1 indicated the attachment of a 4-hydroxyisopentenyl unit and a glucosyl unit to N-3 and N-7, respectively, in the isoguanine unit. The downfield chemical shifts of the ¹H and ¹³C NMR signals attributed to C-2” of the glucosyl unit indicated the attachment of the sulfate group to the position. Thus, the structure of 1 was determined as 2”-sulfated saikachinoside A. Further, the structures of 2 and 3 were elucidated as 2”,4”-disulfated saikachinoside A and 2”,4”-disulfated locustoside B, respectively, on the basis of the spectroscopic data. The isolated compounds were evaluated for their inhibitory activity against hexokinase and acid phosphatase. Compound 2, a major constituent of the pupal case, exhibited 38% of inhibitory activity against hexokinase and 31% of inhibitory activity against acid phosphatase at 1mM. Compound 3 also exhibited 59% of inhibitory activity against hexokinase and 61% against acid phosphatase at 1mM.