Abstract
The antidiabetic potential of Aspalathus linearis has been investigated for over a decade, however, its characterisation remains incomplete with results scattered across numerous journals making the information difficult to compare and integrate. To explore whether any potential antidiabetic mechanisms for A. linearis have been neglected and to compare the suitability of extracts of green and "fermented" A. linearis as potential antidiabetic treatment strategies, this study utilised a comprehensive in vitro antidiabetic target-directed screening platform in combination with high content screening and analysis/cellomics. The antidiabetic screening platform consisted of 20 different screening assays that incorporated 5 well-characterised antidiabetic targets i.e. the intestine, liver, skeletal muscle, adipose tissue/obesity and pancreatic β-cells. Both the green and fermented extracts of A. linearis demonstrated very broad antidiabetic mechanisms as they revealed several promising activities that could be useful in combatting insulin resistance, inflammation, oxidative stress, protein glycation and pancreatic β-cell dysfunction and death - with a strong tendency to attenuate postprandial hyperglycaemia and the subsequent metabolic dysfunction which arises as a result of poor glycaemic control. The green extract was more successful at combatting oxidative stress in INS-1 pancreatic β-cells and enhancing intracellular calcium levels in the absence of glucose. Conversely, the fermented extract demonstrated a greater ability to inhibit α-glucosidase activity as well as palmitic acid-induced free fatty acid accumulation in C3A hepatocytes and differentiated L6 myotubes, however, further studies are required to clarify the potentially toxic and pro-inflammatory nature of the fermented extract.
Highlights
The World Health Organisation has classified diabetes as one of the four priority non-communicable diseases to be targeted for action by global leaders
In order to select suitable experimental concentrations which eliminate the confounding problems associated with cell death and that could be considered biologically relevant, the cytotoxicity of the green and fermented extracts of A. linearis were tested on four different cell lines using Hoechst 33342 (Fig. 1) and propidium iodide (PI) dual-staining
No reports of toxicity for A. linearis at concentrations normally consumed in its tea form have been recorded and it is generally considered safe for consumption.[32]
Summary
The World Health Organisation has classified diabetes as one of the four priority non-communicable diseases to be targeted for action by global leaders. This is largely due to the inaccessibility of affordable treatments for diabetes in many low- and middle-income countries which results in countless complications and premature deaths, placing undue strain on an already overburdened healthcare system.[1] there is an urgent need for the discovery of alternative antidiabetic treatment strategies that are more affordable and accessible to those living in developing countries. Given the substantial repertoire of African medicinal plants used to treat diabetes,[2] and the excessive costs to clinically confirm therapeutic efficacy, few are likely to ever be sufficiently characterised to fully justify their inclusion into healthcare programs. Most studies relating to antidiabetic medicinal plants are based on a trial and error approach, in which animal models are selected based on popularity and 1020 | Food Funct., 2021, 12, 1020–1038
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