Phytochemical constituents, antioxidant and antidiabetic activities of different extracts of the leaves, stem and root barks of Alstonia boonei: an in vitro and in silico study

ABSTRACT

This study investigated the antidiabetic and antioxidant activities of the extracts from three parts of Alstonia boonei. Sequential extraction of leaves, stem and root bark samples was done with the solvents of increasing polarity and these extracts were assayed for total phenolic content and in vitro antioxidant and antidiabetic activities using different experimental models. The electron donating, 1,1-diphenyl-2-picrylhydrazyl (DPPH) and nitric oxide radical scavenging activities of all the extracts were investigated in this study. The ability of these extracts to inhibit α-glucosidase and α-amylase was also examined in vitro. The ethanol extract of leaves showed the highest total phenolic content compared to other extracts. All extracts showed free radical scavenging abilities in different experimental models. The ethanol and aqueous extracts significantly (p < 0.05) inhibited the activities of key enzymes linked to type 2 diabetes. GC-MS analysis of the extracts from different plant parts revealed the presence of sterols, aromatics, aliphatic acids and esters. These compounds showed a high binding affinity with α-glucosidase and α-amylase enzymes under molecular docking studies. Data of this study suggest that the different parts of A. boonei, especially the ethanol and aqueous extracts of leaves, possess potent antioxidant and diabetes related enzymes inhibitory activities that could be further exploited in the development of novel antidiabetic medicines.

KEYWORDS:

• Alstonia boonei
• hyperglycaemia
• medicinal plant
• molecular docking
• oxidative stress

Acknowledgments

The authors would like to appreciate the Research office, University of KwaZulu-Natal, Durban and the National Research Foundation-The World Academy of Science (NRF-TWAS), Pretoria, South Africa for funding this study.

Disclosure statement

The authors declare that there is no conflict of interest in this work.

Additional information

Funding

This work was supported by the University of KwaZulu-Natal, Durban and National Research Foundation- the World Academy of Science (NRF-TWAS), Pretoria, South Africa.

Notes on contributors

Olajumoke A. Oyebode

Dr. OA Oyebode holds a PhD in Biochemistry from the University of KwaZulu -Natal, Durban, South Africa. Her research interests include medicinal plants, type 2 diabetes and oxidative toxicity.

Ochuko L. Erukainure

Dr. OL Erukainure holds a PhD in Biochemistry from the University of KwaZulu-Natal, Durban, South Africa. His research interests include medicinal plants, natural products, neurotoxicity, type 2 diabetes and complications, metabolomics and functional foods.

Collins U. Ibeji

Dr. CU Ibeji holds a PhD in Chemistry from the University of Ibadan, Ibadan, Nigeria and an academic at the Department of Chemistry, University of Nigeria, Nsukka, Nigeria. His research interests include bioinformatics.

Neil A. Koorbanally

Prof. NA Koorbanally is an a Professor at the Department of Chemistry, School of Chemistry and Physics, University of KwaZulu-Natal, Durban, South Africa. His research interests include natural products and synthesis.

Md. Shahidul Islam

Prof. MS Islam is an Associate Professor of Biochemistry and Academic Leader of the Biotechnology Cluster at the Westville Campus of the University of KwaZulu-Natal, Durban, South Africa. His major research area of interests are animal model, type 2 diabetes, obesity, functional and medicinal foods, natural and artificial sweeteners and medicinal plants.