Type 2 diabetes (T2D) is a chronic metabolic disorder, and the incidence of T2D increases at an alarming rate and constitutes a global health problem. In this context, the use of plants as a source for inhibitors of α-glucosidase, an enzyme involved in carbohydrate metabolism in the brush border of the small intestines, seems an attractive approach [1]. The genus Picramnia shows high diversity of secondary metabolites, such as anthrones, oxanthrones, anthraquinones, coumarins, and triterpenes [2]. In our on-going screening programme for antidiabetic compounds from plants, the ethanolic extract of P. glazioviana showed an inhibitory concentration (IC50) of 27.31 µg/mL towards α-glucosidase, and was therefore selected for further investigation. This extract was subjected to liquid-liquid partitioning, and the ethyl acetate and dichloromethane fractions showed IC50 values of 15.11 µg/mL and 38.44 µg/mL, respectively. The ethyl acetate fraction was investigated with high-resolution α-glucosidase inhibition profiling combined with LC-HRMS. This disclosed two flavonoids, catechin and epicatechin, which have previously been reported to have α-glucosidase inhibitory activity [1]. The dichloromethane fraction was investigated with a combination of HPLC-HRMS-SPE-NMR and preparative-scale HPLC. This disclosed six new nortriterpenes named picravianes A-F. The results show that plants of the genus Picramnia are a valuable source of new and bioactive compounds.
Acknowledgements: FAPESP is acknowledged for a sandwich PhD scholarship to Leila Gimenes and Arife Önder is thanked for technical assistance.
Keywords: Picramnia glazioviana, nortriterpenes, HPLC-HRMS-SPE-NMR, α-glucosidase
References:
[1] Kim TH. A novel α glucosidase inhibitory constituent from Uncaria gambir. J Nat Med 2016; 70:811-815.
[2] Rodríguez-Gamboa T, Fernandes JB, Filho ER, Da Silva MFGF, Vieira PC, Barrios Ch M, Castilho OC, Victor SR, Pagnocca FC, Bueno OC, Hebling MJA. Triterpene benzoates from the bark of Picramnia teapensis (Simaroubaceae) J Braz Chem Soc 2001; 12:386-390.