Protein tyrosine phosphatase 1B (PTP1B) inhibitory activity and glucosidase inhibitory activity of compounds isolated from Agrimonia pilosa

Abstract

Context: Despite phytochemical studies of Agrimonia pilosa Ledeb. (Rosaceae), the antidiabetic effects of this plant are unknown.

Objective: This study characterizes the isolated compounds from the aerial parts of A. pilosa and evaluates their PTP1B and α-glucosidase inhibitory properties.

Materials and methods: Ethanol extract of A. pilosa was found to inhibit 64% PTP1B activity at 30 μg/mL. The ethanol extract was partitioned with methylene chloride, ethyl acetate, n-butanol, and water fractions. Among these, the ethyl acetate fraction displayed the most potent PTP1B activity. The ethyl acetate extract was separated by chromatographic methods to obtain flavonoids and triterpenoids (1–11); which were evaluated for their inhibitory effects on PTP1B activity with p-nitrophenyl phosphate (p-NPP) as a substrate, and also α-glucosidase enzyme.

Results: Compounds 1–11 were identified as apigenin-7-O-β-d-glucuronide-6″-methyl ester, triliroside, quercetin-7-O-β-d-glycoside, quercetin-3-O-β-d-glycoside, kaempferol, kaempferol-3-O-α-l-rhamnoside, β-sitosterol, ursolic acid, tormentic acid, methyl 2-hydroxyl tricosanoate, and palmitic acid. Compounds 8, 9, and 11 displayed inhibitory effects on PTP1B activity with IC₅₀ values of 3.47 ± 0.02, 0.50 ± 0.06, and 0.10 ± 0.03 μM, respectively. Compounds 3, 4, 6, and 9 exhibited inhibition of the α-glucosidase activity with IC₅₀ values of 11.2 ± 0.2, 29.6 ± 0.9, 28.5 ± 0.1, and 23.8 ± 0.4 μM, respectively.

Discussion and conclusion: As major ingredients of A. pilosa, compounds 1, 6, 8, and 9 showed the greatest inhibitory potency on PTP1B activity. Compounds 3, 6, 8, and 9 also showed potent inhibitory effects on α-glucosidase enzyme. This result suggested the potential of these compounds for developing antidiabetic agents.

• Flavonoid glycosides
• glucosidase inhibitors
• PTP1B inhibitors
• triterpenoids

Acknowledgements

The authors are grateful to the Korea Basic Science Institute (KBSI) for mass spectrometric measurements.

Declaration of interest

The authors declare no competing financial interest. This research was supported by the research grants, funded by the Catholic University of Daegu, in 2013.