High-resolution α-glucosidase inhibition profiling and HPLC-HRMS-SPE-NMR for phytochemical investigation and identification of antidiabetic constituents in Picramnia glazioviana

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.

Fig. 1

FAPESP is acknowledged for a sandwich PhD scholarship to Leila Gimenes and Arife Önder is thanked for technical assistance.

[1] Kim TH. 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. J Braz Chem Soc 2001; 12:386 – 390.