Geranylated 2-arylbenzofurans from Morus alba var. tatarica and their α-glucosidase and protein tyrosine phosphatase 1B inhibitory activities

Ten new geranylated 2-arylbenzofuran derivatives, including two monoterpenoid 2-arylbenzofurans (1 and 2), two geranylated 2-arylbenzofuran enantiomers (3a and 3b), and six geranylated 2-arylbenzofurans (4–9), along with four known 2-arylbenzofurans (10–13) were isolated from the root bark of Morus alba var. tatarica. Their structures and relative configurations were established on the basis of spectroscopic data analysis. Compounds 3–7 with one asymmetric carbon at C-7″ were supposed to be enantiomeric mixtures confirmed by chiral HPLC analysis, and the absolute configurations of each enantiomer in 3–7 were determined by Rh2(OCOCF3)4-induced CD and Snatzke's method. The enantiomers with the substituting group at C-2′ exhibited better resolutions on a Chiralpak AD-H column than those with the substituting group at C-4′. Compounds 1–7, 10, 11 and 13, showed α-glucosidase inhibitory activities with IC50 values of 11.9–131.9 μM, and compounds 1 and 9–13 inhibited protein tyrosine phosphatase 1B (PTP1B) with IC50 values of 7.9–38.1 μM.

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