Isolation, Structural Elucidation, and α-Glucosidase Inhibitory Activities of Triterpenoid Lactones and Their Relevant Biogenetic Constituents from Ganoderma resinaceum

Abstract

Ganoderma resinaceum has been used as an ethnomedicine for lowering blood sugar. To clarify the bioactive chemical constituents contributing to lower blood sugar, chemical investigation on the fruiting bodies of Ganoderma resinaceum was conducted by chromatographic techniques, and led to the isolation of 14 compounds. Their structures were elucidated as triterpenoid lactones (1–4 and 8) and ganoderma acids (5–7 and 9–14) based on the analysis of extensive spectroscopy (mass spectrometry (MS), nuclear magnetic resonance (NMR), infrared (IR), and ultraviolet (UV)) and comparison with literature data. Compounds 3, 5, 6, and 9–14 were evaluated for α-glucosidase inhibitory activity. Compounds 1–7 are new compounds. Compounds 1–4 and 8 were characteristic of an oxaspirolactone moiety, consisting of a five-membered ether ring, a five-membered lactone ring, and a characteristic C-23 spiro carbon. It is rare for natural products that such an oxaspirolactone moiety occurred in the lanostane-type triterpenoids. Compounds 5–7 and 9–14 may be important intermediates of the biosynthetic pathways of 1–4 and 8. Compounds 1 and 2 showed more potent inhibitory activity against α-glucosidase compared with the positive control drug acarbose with IC50 value of 0.75 ± 0.018 mM and 1.64 ± 0.022 mM, respectively.

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“… [ 282 ] 3 Ganoderma resinaceum Triterpenoid lactones α-glucosidase inhibitor An in vitro α-glucosidase inhibitory assay Compounds 1 and 2 were more potent α-glucosidase inhibitors than acarbose, with IC50 values of 0.75 ± 0.018 mM and 1.64 ± 0.022 mM, respectively. [ 44 ] 4 Cyclocarya paliurus Triterpenoid glycosides isolated from leaves ethanol extract Increase glucose uptake via AMPK/p38 pathways An in vitro study in 3T3-L1 adipocytes and C2C12 myotubes Compound 1 significantly enhanced insulin-stimulated glucose uptake in 3T3-L1 adipocytes and C2C12 myotubes. The promising mechanisms of compound 1 in enhancing glucose uptake in cells are upregulating the AMP-activated protein kinase (AMPK)-p38 pathways.…”