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The α-glucosidase and maltase inhibitory effects of Punica granatum L. flowers (PGF) were investigated. The methanol extract (PGFMe), n-hexane extract (PGFH), chloroform extract (PGFC) and the remaining water fraction (PGFW) were assayed for their α-glucosidase and maltase inhibitory effects. PGFW showed potent α-glucosidase inhibition with IC₅₀ of 0.8 μg/mL followed by PGFMe (IC₅₀ of 4.0 μg/mL) then PGFC (IC₅₀ of 5.21 μg/mL) in comparison to acarbose (0.9 μM). Due to its selectivity towards α-glucosidase, PGFC was subjected to bioactivity-guided isolation of its main active constituents. Five known compounds (1-5) were identified as β-sitosterol (1), oleanolic acid (2), ursolic acid (3), p-coumaric acid (4) and apigenin (5). Ursolic and oleanolic acids showed potent α-glucosidase inhibition (IC₅₀ of 39.0 and 35.0 μM, respectively), while they did not show significant maltase inhibition. Kinetic study using the double Lineweaver-Burk plot revealed that ursolic acid uncompetitively inhibited α-glucosidase in comparison with acarbose as a competitive inhibitor.

BackgroundGurigumu-7 is an important traditional Mongolian medicine frequently used for liver diseases. However, the pharmacological effects and the bioactive constituents are not well understood.MethodThis research was to use CCl4-induced liver damage in mice to investigate the hepatoprotective effects of Gurigumu-7 and the methanol eluted fraction from a DIAION column of an extract of Gurigumu-7 (MF). The chemical constituents of MF were analyzed by UPLC-MS.ResultsPretreated orally with MF (66, 132 and 264 mg/kg) once a day for 4 days dose-dependently suppressed CCl4-induced mice liver histopathological changes and serum aminotransferase activities (alanine transaminase: 1144.0 ± 787.2 v.s. 2461.8 ± 1072.7 U/L, p < 0.05; aspartate transaminase: 1173 ± 785.3 v.s. 2506.6 ± 1140.7 U/L, p < 0.01). MF treated group demonstrated increased levels of SOD (108.19 ± 30.32 v.s. 75.75 ± 5.37 U/mg protein, p < 0.01) but decreased levels of malonyldialdehyde (7.68 ± 1.95 v.s. 44.32 ± 16.68 nmol/mg protein, p < 0.01) compared to the CCl4 control group. More than 30 chemical constituents were quantified, and MF was found to be rich in ellagic acid (297.97 mg/g), luteolin and its glucosides (35.10 mg/g), apigenin and its glucosides (>30 mg/g), ursolic acid (14.91 mg/g), bidenoside C (8.75 mg/g), and proanthocyanidins (15.64 mg/g in proanthocyanidin A2 equivalent).ConclusionThe methanol eluted fraction (MF) from a DIAION column of an extract of the Mongolian medicine-Gurigumu-7 was found to be more hepatoprotective than Gurigumu-7. The results suggested that MF is a promising bioactive fraction for the development of new hepatoprotective medicine with better formulation and quality control properties.