Inhibitory activity of Aralia continentalis roots on protein tyrosine phosphatase 1B and rat lens aldose reductase.

As part of our continuous search for compounds from natural sources that can treat diabetes and its diabetic complications, in the present work, we investigated the protein tyrosine phosphatase 1B (PTP1B) and rat lens aldose reductase (RLAR) inhibitory activities of the roots of Aralia continentalis. The methanol extract showed a potent inhibitory activity against PTP1B and RLAR. Among the tested fractions, the n-hexane fraction exhibited the highest PTP1B inhibitory activity, while the EtOAc fraction showed highest RLAR inhibitory activity. Bioassayguided fractionation of the active n-hexane and EtOAc soluble fractions resulted in the isolation of the diterpenoids; ent-pimara-8(14),15-diene-19-oic acid (continentalic acid, 1); ent-kaur-16-en-19-oic-acid (kaurenoic acid, 2); ent-pimara-8(14),15-diene-19-ol (3); 7-oxo-ent-pimara-8(14),15-diene-19-oic acid (4); 16á-hydroxy-17-isovaleroyloxy-ent-kauran-19-oic acid (5); 17-hydroxy-entkaur-15-en-19-oic acid (6); 15á,16á-epoxy-17-hydroxy-ent-kauran-19-oic acid (7); 16á,17-dihydroxy-ent-kauran-19-oic acid (8); 8á-hydroxy-ent-pimara-15-en-19-ol (9); 4-epirulopezol (10) and 4â-hydroxy-19-nor-(-)-pimara-8(14),15-diene (11), from the n-hexane fraction, and 4-[formy-5-(methoxymethyl)-1H-pyrrol-1-yl] butanoic acid (12); vanillic acid (13); 4-hydroxybenzoic acid (14); protocatechuic acid (15); nicotinic acid (16); aralia cerebroside (17); 5-O-feruloly quinic acid (18) from the EtOAc fraction. Of these, compounds 12∼14, 16 and 18 were isolated from A. continentalis for the first time. Compounds 1∼10 exhibited inhibitory potential against PTP1B, while compounds 12, 17, and 18 were found to be active against RLAR. Taken together, these results clearly demonstrate that the roots of A. continentalis displayed anti-diabetic and antidiabetic properties, which could be further explored to develop therapeutic and preventive agents for the treatment of diabetes and related complications.