In vitro α-amylase, α-glucosidase, lipase inhibitory and cytotoxic activities of tuber extracts of Kedrostis africana (L.) Cogn

Abstract

Kedrostis africana, is a tuberous plant commonly used by traditional healers in the Eastern Cape Province of South Africa for the management of obesity. The aim of this study was to investigate the antiobesity and cytotoxic effects of Kedrostis africana extracts in vitro The α-amylase, α-glucosidase and lipase inhibitory activities of aqueous and ethanol extracts of Kedrostis africana tuber were investigated while the cytotoxic effects of these extracts were analyzed using Hoechst 33342 and propidium iodide (PI) dual staining in combination with Molecular Devices ImageXpress Micro XLS Widefield microscope for high content analysis on human cervical (HeLa) cell line. The ethanol extract exhibited the strongest inhibitory effect on pancreatic lipase (IC₅₀ = 381.86 μg/ml) and on α-glucosidase (IC₅₀ = 157.99 μg/mL) while the aqueous extract has strongest α-amylase (IC₅₀ = 439.45 μg/ml). Both tuber extracts were found nontoxic at tested concentrations on HeLa cell lines as confirmed by the Hoechst 33342 and propidium iodide dual staining respectively. This study revealed that both the aqueous and ethanol tuber extract of K. africana exerts a certain degree of inhibitory effect on α-amylase, α-glucosidase and lipase and were also nontoxic to HeLa cell line at tested concentrations.

Keywords: Biochemistry; Biotechnology.

Fig. 1

Fluorescent micrographs captured during the cytotoxicity screening assay comparing the untreated sample with the aqueous and ethanol extract of K. africana for HeLa cells using Hoechst 33342 (blue) and propidium iodide (red).

Fig. 2

Cytotoxicity screening of Kedrostis africana (A) cell number with (B) cell density for HeLa cells; live- and dead cell numbers were obtained from Hoechst 33342 and PI staining, respectively and cell density from crystal violet staining. Results are reported as means ± SD where each experiment was performed three times, each in triplicate (*p < 0.05; **p < 0.01; ***p < 0.005 compared to untreated sample).

Fig. 3

α-amylase inhibitory activity of the aqueous and ethanol extracts of Kedrostis africana. Values are mean ± SD (n = 3). Mean separation by LSD (p < 0.05). Set of bars (the same concentration) with different alphabets are different. *Lower than acarbose (positive control). SD: Standard deviation; LSD: Least Significant Difference.

Fig. 4

α-Glucosidase inhibitory activity of the aqueous and ethanol extracts of Kedrostis africana. Values are mean ± SD (n = 3). Mean separation by LSD (p < 0.05). Set of bars (the same concentration) with different alphabets are different. ^∗Lower than the positive control EGCG: Epigallocatechin gallate; SD: Standard deviation; LSD: Least Significant Difference.

Fig. 5

Lipase inhibitory activity of the aqueous and ethanol extracts of Kedrostis africana. Values are mean ± SD (n = 3). Mean separation by LSD (p < 0.05). Set of bars (the same concentration) with different alphabets are different. ^∗Lower than the positive control (Orlistat). SD: Standard deviation; LSD: Least Significant Difference.