Pyrrolidine-type iminosugars from leaves of Suregada glomerulata

• Six new pyrrolidine-type iminosugars along with four known ones were isolated from the leaves of Suregada glomerulata.
• The new compounds 4–6 and 8 were characterized as rarely seen 4-deoxy pyrrolidine-type iminosugars.
• The discovery of new compounds 9 and 10 with a C8 side chain expands the distribution of pyrrolidine-type iminosugars with a long-side chain in plants.
• The 8-hydroxyoctyl side-chain represents a new addition for the molecular diversity of iminosugars.

Phytochemical investigation of the H2O extract of leaves of Suregada glomerulata led to the isolation of ten pyrrolidine-type iminosugars. The chemical structures of the six new compounds (4–6, 8–10) were elucidated as 2,5-imino-2,4,5-trideoxy-d-manno-heptitol (4-deoxy-homoDMDP) (4), 2,5-imino-2,4,5-trideoxy-d-gulo-heptitol (5), 2,5-imino-2,4,5,6-tetradeoxy-d-gulo-heptitol (6), 6-C-butyl-4-deoxy-DMDP (8), 6-C-(8-hydroxyoctyl)-DMDP (9), and 6-C-(8-hydroxyoctyl)-2,5-dideoxy-2,5-imino-d-galactitol (10), respectively, on the basis of spectroscopic data analysis (NMR and HRESIMS). Compounds 4–6 and 8 were characterized as rarely seen 4-deoxy pyrrolidine-type iminosugars. Pyrrolidine-type iminosugars with a long-side chain have been found in the restrictive plant families Moraceae, Campanulaceae, and Hyacinthaceae. The discovery of compounds 9 and 10 with a C8 side chain from S. glomerulata (Euphorbiaceae) expands the range of distribution for the iminosugars in plants. The 8-hydroxyoctyl side-chain represents a new addition for the molecular diversity of iminosugars. The compounds 1–10 were evaluated for inhibitory activity against rat intestinal α-glucosidase. However, all the test compounds showed no significant inhibitory activities to the glucosidase.

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