In vitro profiling and functional assessments of the anti‐diabetic capacity of phenolic‐rich extracts of Bulbine natalensis and Bulbine frutescens

• Published in: Diabetic medicine 2023-02, Vol.40 (2), p.e14770-n/a
• Main Authors: Oyedemi, Sunday O., Atanes, Patricio, Aiyegoro, Olayinka A., Amoo, Stephen O., Swain, Shasank S., Persaud, Shanta J.
• Format: Article
• Language: English
• Subjects: Acids; alpha-Amylases; alpha-Glucosidases - metabolism; Animals; Antidiabetics; Antioxidants - chemistry; Antioxidants - pharmacology; Asphodelaceae; Bulbine; Ca2+/calmodulin-dependent protein kinase II; Cell viability; Diabetes; Diabetes mellitus (non-insulin dependent); Diabetes Mellitus, Type 2 - metabolism; Dipeptidyl Peptidase 4; glucoregulatory enzymes; Glucose; Glycoside Hydrolase Inhibitors; Insulin; Insulin secretion; Lipase; Mice; minerals; molecular docking; Molecular Docking Simulation; Pancreas; Phenolic acids; Phenols - pharmacology; plant extracts; Plant Extracts - chemistry; Plant Extracts - pharmacology; Potassium ferricyanide; Protein kinase A; Protein kinase C; Protocatechuic acid; Secretion; Spectroscopy
• ISSN: 0742-3071; 1464-5491
• DOI: 10.1111/dme.14770

Aims Bulbine natalensis (BN) and Bulbine frutescens (BF) are recommended in South African traditional medicine to treat diabetes, but their modes of action are unknown. This study assessed the phenolic acid profiles, mineral composition and in vitro functional effects of BN and BF to better understand their glucose‐lowering capabilities. Methods Phenolic acid and mineral composition of BN and BF methanolic extracts were determined by HPLC and inductively coupled plasma optical emission spectroscopy respectively. Antioxidant capacity was assessed by potassium ferricyanide reducing power and 2,2‐diphenyl‐2‐picrylhydrazyl radical scavenging assays, and inhibition of alpha‐amylase, alpha‐glucosidase, pancreatic lipase and DPP4 was evaluated by standard enzyme assays. The effects of BN and BF extracts on insulin secretion were investigated using static incubations of isolated mouse islets and molecular docking analysis was used to identify interactions of BN and BF with partners that could mediate stimulatory effects on insulin secretion. Results Methanolic extracts of BN and BF contained high concentrations of protocatechuic and gallic acids, and high levels of Zn, Mn and Cr. The extracts inhibited alpha‐glucosidase, alpha‐amylase, pancreatic lipase and DPP4 activities, and they also inhibited free radical generation. Both extracts significantly potentiated glucose‐stimulated insulin secretion without significantly affecting basal insulin secretion or islet cell viability. Protocatechuic acid, the most abundant phenolic acid in the extracts, showed high affinity for PKA, PKC, DPP4 and CaMK II in the docking analysis. Conclusions BN and BF have multiple beneficial effects on glucoregulatory pathways and they, or their derivatives, could be developed to treat type 2 diabetes.