Nanoformulation of Leonotis leonurus to improve its bioavailability as a potential antidiabetic drug

Abstract

Nanostructured lipid carriers (NLCs) of Leonotis leonurus were successfully produced using high-pressure homogenisation (HPH) on a LAB 40 homogeniser. The particle size was determined for the formulation as well as short-term stability study. The formulation was exposed to Chang liver cells for a glucose uptake study and to INS-1 cells for a chronic insulin release study under normoglycaemic and hyperglycaemic conditions. The particle size of the extract NLC was 220 nm with a PdI of 0.08 after homogenisation at 800 bar. The formulation was stable at the tested temperatures. The extract NLC formulation at 1 µg/ml improved glucose uptake, relative to the control liver cells. Insulin release in INS-1 cells was also elevated under hyperglycaemic conditions when exposed to the NLCs, in comparison with the control untreated cells and the non-formulated extract. The plant extract encapsulated in NLC improved the uptake of glucose and enhanced the insulin sensitivity in vitro, compared to the extract.

Keywords: Insulin; Leonotis leonurus; Nanostructured lipid carriers; Type 2 diabetes.

Fig. 1

PCS (a) and LD diameters b of L. leonurus NLC produced by HPH after five homogenisation cycles, at 800 bar at 80 °C. Mean particle size and polydispersity indices (PdI) are shown

Fig. 2

A photomicrograph (a) and a scanning electron micrograph (b) of L. leonurus encapsulated NLC. SEM magnification: ×4.61; scale bar = 10 µm

Fig. 3

Short-term physical stability profile of the particle size diameter of L. leonurus extract NLC at temperatures, 4 °C, room temperature (± 25 °C) and 40 °C at the day of production and at the 7th, 14th, 28th and 60th day. Mean particle sizes are not significantly different at temperatures tested

Fig. 4

MTT assays of L. leonurus extract NLC (0.25–10 µg/ml). Extract concentration used was 10 µg/ml. NLC blank formulation at 10 µg/ml in INS-1 cells (a) and Chang liver cells (b), Met metformin, Ext L. leonurus extract

Fig. 5

Insulin-stimulated glucose uptake measured in the presence of 60 µU/ml insulin and L. leonurus NLC (0.25–10 µg/ml). Met (1 µM) was used as a positive control and the Ext that represents extract (10 µg/ml) was used as a reference treatment in relation to the formulations. The untreated samples only had the presence of media. Error bars represent ± SEM of n = 3, *P < 0.05 versus untreated (control). ^# P < 0.01 versus untreated (control)

Fig. 6

Chronic insulin release in INS-1 cells completed under normo- and hyperglycaemic conditions for a 48-h exposure of the NLC at varying concentrations (0.25–10 µg/ml). Data are expressed as the mean ± SEM (n = 3), #P < 0.05 versus control normoglycaemia (11.1 mM) treatment, *P < 0.05 versus untreated (control) hyperglycaemia (33.3 mM). Sul sulfonylurea, positive control. Ext L. leonurus extract 10 µg/ml