Constituents of the Flower of Maxillaria tenuifolia and Their Anti-Diabetic Activity

The EtOAc extract of the flower of Maxillaria tenuifolia, which had shown potent α-glucosidase inhibitory, was subjected to activity-guided isolation to yield four compounds, 3,4-dihydroxy benzoic acid methyl ester (1), flavanthridin (2), vanillic acid (3) and mangiferin (4).  Their structures were ascertained by comparison of their physical and spectroscopic properties with those reported in the literature.  Among them, flavanthridin (2), vanillic acid (3) and mangiferin (4) showed significant α-glucosidase inhibitory activity compared to acarbose at the concentration 1.0 mg/mL.  Besides, 3,4-dihydroxy benzoic acid methyl ester (1) and mangiferin (4) also showed more effective in against the peroxidation of linoleic acid in an aqueous system than trolox.  These results indicated that the EtOAc extract of M. tenuifolia and the related constituents might have anti-diabetic effect by suppressing carbohydrate disintegration and could prevent damage to organisms by oxidative stress.