Medicinal properties of Abrus precatorius L. leaf extract: antimicrobial, cytotoxicity and carbohydrate metabolising enzymes’ inhibitory potential

Abstract

In this study, leaf extract of Abrus precatorius was evaluated for its cytotoxic, antimicrobial and anti-diabetic activities. The antimicrobial activities were evaluated via agar well diffusion and agar dilution methods while the cytotoxic activity of the extract was determined using brine shrimp lethality assay. For the anti-diabetic study, varying concentrations of the extract were pre-incubated each with α-glucosidase and α-amylase followed by the addition of p-nitrophenylglucopyranoside and starch, respectively. The lowest and widest inhibitory zones exhibited by the extract were 16.00±0.00 and 22.00±0.58 mm, respectively, while minimum inhibitory concentrations (MICs) ranged between 1.56 and 3.13 mg/mL and the minimum bactericidal concentrations (MBCs) ranged between 3.13 and 6.25 mg/mL. Within 15  min of contact time, the percentages of eliminated bacteria cells were 43.82% (Escherichia coli (ATCC839)) and 33.99% (Enterococcus faecalis) at a concentration of 1×MIC, while total elimination was achieved at 3×MIC after 120 and 90  min against E. coli and E. faecalis, respectively. In vitro anti-diabetic analysis revealed that the extract exhibited potent and moderate non-competitive inhibitory effects against α-glucosidase and α-amylase, respectively. The inhibitions were dose-specific with respective IC₅₀ values of 1.11 and 5.66 mg/mL compared with 3.08 and 3.61 mg/mL for the control. Judging by the respective LC₅₀ and LC₉₀ values of 265.23 µg/mL and 743.40 µg/mL for the brine shrimp lethality assay, the extract could also be considered potent. It is thereby evident from the data presented that A. precatorius is rich in chemotherapeutic constituents that could be potentially useful for the development of antibacterial and hypoglycaemic drugs.

Keywords:

• acarbose
• α-amylase, α-glucosidase, inhibition zones
• killing rate
• MICs
• MBCs

ACKNOWLEDGEMENTS

The expertise and support rendered at the laboratory of Phytomedicine and Phytopharmacology Research Group, University of the Free State, Qwaqwa campus, is gracefully acknowledged.

We declare that this work was done by the authors named in this article and all liabilities pertaining to claims relating to the content of this article will be borne by the authors. AOTO conceptualised the study. Sample collection, experimental assays and data analysis were performed by KAA and SS. They both drafted the manuscript which was reviewed and approved by all authors.

CONFLICT OF INTEREST

No conflict of interest is associated with this work