The antioxidant and antidiabetic potentials of polyphenolic-rich extracts of Cyperus rotundus (Linn.)

Abstract

In this study, the rhizome of Cyperus rotundus L was investigated for its antioxidant and antidiabetic effects using in vitro and in silico experimental models. Its crude extracts (ethyl acetate, ethanol and aqueous) were screened in vitro for their antioxidant activity using ferric-reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH), as well as their inhibitory effect on α-glucosidase enzyme. Subsequently, the extracts were subjected to Gas Chromatography-Mass Spectrometry (GC-MS) analysis to elucidate their possible bioactive compounds. Furthermore, computational molecular docking of selected phenolic compounds was conducted to determine their mode of α-glucosidase inhibitory activity. The aqueous extract displayed the highest level of total phenolic content and significantly higher scavenging activity in both FRAP and DPPH assays compared to ethyl acetate and ethanol extracts. In FRAP and DPPH assays, IC₅₀ values of aqueous extract were 448.626 µg/mL and 418.74 µg/mL, respectively. Aqueous extract further presented higher α-glucosidase inhibitory activity with an IC₅₀ value of 383.75 µg/mL. GC-MS analysis revealed the presence of the following phenolic compounds: 4-methyl-2-(2,4,4-trimethylpentan-2-yl) phenol, Phenol,2-methyl-4-(1,1,3,3-tetramethylbutyl)- and 1-ethoxy-2-isopropylbenzene. Molecular docking study revealed 1-ethoxy-2-isopropylbenzene formed two hydrogen bonds with the interacting residues in the active site of α-glucosidase enzyme. Furthermore, 4-methyl-2-(2,4,4-trimethylpentan-2-yl) phenol had the lowest binding energy inferring the best affinity for α-glucosidase active site. These results suggest the possible antioxidant and antidiabetic potential of Cyperus rotundus.

Communicated by Ramaswamy H. Sarma

Keywords:

• Antioxidant
• antidiabetic
• Cyperus rotundus L.
• molecular docking

Acknowledgement

The authors would like to acknowledge the Competitive Research Grant from the Research Office, University of KwaZulu-Natal, Durban; and Funding for Rated and Young Researchers from the National Research Foundation (NRF), Pretoria, South Africa.

Disclosure statement

No potential conflict of interest was reported by the authors.