Fluorescence sensing and glycosidase inhibition effect of multivalent glycosidase inhibitors based on Naphthalimide-deoxynojirimycin conjugates.

Synthetic glycoconjugates as chemical probes have been widely developed for the detection of glycosidase enzymes. However, the binding interactions between iminosugar derivatives and glycosidases were limited, especially for the binding interactions between multivalent glycosidase inhibitors and α-glycosidases. In this paper, three naphthalimide-DNJ conjugates were synthesized. Furthermore, the binding interactions and glycosidase inhibition effects of them were investigated. It was found that the strong binding interactions of multivalent glycosidase inhibitors with enzymes were related to the efficient inhibitory activity against glycosidase. Moreover, the lengths of the chain between DNJ moieties and the triazole ring for the naphthalimide-DNJ conjugates influenced the self-assembly properties, binding interactions and glycosidase inhibition activities with multisource glycosidases. Compound 13 with six carbons between the DNJ moiety and triazole ring showed the stronger binding interactions and better glycosidase inhibition activities against α-mannosidase (jack bean) and α-glucosidase (aspergillus niger). In addition, compound 13 showed an effective PBG inhibition effect in mice with 51.18 % decrease in blood glucose at 30 min. This result opens a way for detection of multivalent glycosidase inhibition effect by a fluorescent sensing method.

Multivalent glucosidase inhibitors based on perylene bisimide and iminosugar conjugates.

Although multivalent glucosidase inhibitors based on iminosugars have shown enhanced inhibition activity, an effective way to improve their hypoglycemic effect in vivo, is still in infancy and needs further development. In this paper, PBI-5DNJ and PBI-6DNJ, with three or four DNJ moieties respectively conjugated at the bay position were synthesized. PBI-6DNJ evidenced stronger π-π stacking interactions and, when self-assembled, a smaller size than that of PBI-5DNJ. It was found that PBI-6DNJ exhibited superior α-glucosidases (from mice) inhibition activity (Ki = 0.14 ± 0.007 µM) in vitro than that (Ki = 0.31 ± 0.01) of PBI-5DNJ and in vivo hypoglycemic effects in mice models. PBI-6DNJ possessed good hypoglycemic effects with the percentages of PBG levels of 40.40 ± 3.33% and 39.23 ± 4.84% at a dose of 2.0 mg/kg after 15 min and 30 min of administration, respectively. In terms of measuring percentage decrease of PBG level per DNJ unit, PBI-6DNJ displayed a 2.1-fold enhancement than miglitol, demonstrating a consistency between in vitro and in vivo experiments. This paves the way to the connection between in vivo hypoglycemic potency and in vitro glucosidase inhibition assay, leading to reliable and simplified assessment of hypoglycemic potency determination, and opening a basic understanding of the design of multivalent glucosidase inhibitors.