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Three new ent -kaurane diterpenoids, namely annoglabrin A-C ( 1-3 ), were isolated from the Annona glabra fruit pulp. Their structures were clarified by widespread spectroscopic analyses (1D and 2D NMR, HRESIMS). The relative configuration of these new compounds was established through the NOESY spectrum. Compounds 1-3 were evaluated for their inhibitory activity against α- glucosidase and were found with weak ( 1 and 3 ) or no effects ( 2 ), compared to those of positive control (acarbose, IC 50 82.0 µM).

A new spiroterpenoid, namely tinctorin ( 1 ), along with one known compound, norreticulatin ( 2 ), were isolated from the lichen Parmotrema tinctorum (Despr. ex Nyl.) Hale. Their structures were elucidated by extensive spectroscopic analyses and electronic circular dichroism (ECD) calculations. The absolute configuration of 2 was established for the first time. Compound 1 was evaluated for its inhibitory activity against α- glucosidase and found to be inactive.

This phytochemistry investigation on the trunk of Morus alba L. resulted in the isolation of three triterpenoids, including a new gammacerane triterpenoid - morusacerane ( 1 ); along with two known compounds of betulinic acid ( 2 ) and ursolic acid ( 3 ). The structure elucidation was thoroughly conducted based on 1D, 2D-NMR and HRESIMS spectra, followed by a comparison with existing literatures. The evaluation on α -glucosidase inhibitory exhibited the great potential of the application of these isolated compounds in diabetes treatments. The results show that morusacerane ( 1 ), betulinic acid ( 2 ), and ursolic acid ( 3 ) demonstrate the strong inhibitory with the IC 50 values of 106.1, 11.12, and 7.20 μM, respectively. All of these compounds interacted well with the allosteric site enzyme α -glucosidase MAL32 through H-bonds and hydrophobic interaction.

Two new hopan-type triterpenoids, namely tinctoric acid A-B ( 1-2 ), were isolated from the lichen Parmotrema tinctorum (Despr. ex Nyl.) Hale. Their structures were elucidated by extensive spectroscopic analyses (1D and 2D NMR). The absolute configuration at C-22 of 1 was established through DP4 probability. Compounds 1-2 were evaluated for their inhibitory activity against α- glucosidase and found to be more potent than those of positive control (acarbose, IC 50 168 µM) with values IC 50 74.7 and 98.2 µM, respectively. Both of these compounds interacted well with enzyme α-glucosidase MAL32 through H-bonds and hydrophobic interaction.