A pinitol-rich Glycyrrhiza glabra L. leaf extract as functional supplement with potential in the prevention of endothelial dysfunction through improving insulin signalling

Abstract

Background: Glycyrrhyza glabra L. is one of the most popular medicinal plant in the world, its roots having been used since ancient times in many traditional medicines. On the contrary, scarce attention has been dedicated to liquorice aerial parts. Previous studies showed the presence of a large group of polyphenols and a consistent amount of d-pinitol in the leaf extract.

Methods: The methanolic extract from G. glabra leaves was profiled for its content in polyphenols; the amount of d-pinitol was also measured with two independent methods (HPLC-ELSD and NMR). The extract was tested for its in vitro protective effects against insulin resistance-related endothelial dysfunction in human umbilical vein endothelial cells exposed to palmitic acid, which is the most prevalent saturated free fatty acid in circulation.

Results: Methanolic extract from liquorice leaves has a protective effect against the lipotoxicity-associated alterations of insulin pathway in human endothelial cells, similarly to what observed with pure d-pinitol.

Conclusions: Liquorice leaves are to be considered a waste product which gives a phytocomplex endowed with interesting potential therapeutic properties, moreover the use of a liquorice leaves phytocomplex rather than a pure compound allows avoiding a series of isolation/purification procedures and can be easily scaled up for industrial applications.

Keywords:

• Glycyrrhiza glabra L.
• insulin resistance
• metabolic disease
• d-pinitol
• polycystic ovary syndrome

Acknowledgements

The authors are grateful to Dr. Irene Sangiorgio for her valuable contribution to this work while preparing her degree thesis and to Dr. Sandro Dattilo (IPCB-CNR, CT, Italy) for the facilities in using the HPLC/ESI-MS instrument. The authors are also grateful to Mrs. Tonia Strano and Mr. Antonio Greco (ICB-CNR, CT, Italy) for their skilful technical assistance.

Disclosure statement

The authors declare that they have no competing financial interests regarding the work reported in this paper.

Additional information

Funding

The work was financially supported by the Consiglio Nazionale delle Ricerche (CNR Rome, Italy).