A comprehensive in-vitro/in-vivo screening toolbox for the elucidation of glucose homeostasis modulating properties of plant extracts (from roots) and its bioactives

Plant extracts are increasingly recognized for their potential in modulating (postprandial) blood glucose levels. In this context, root extracts are of particular interest due to their high concentrations and often unique spectrum of plant bioactives. To identify new plant species with potential glucose-lowering activity, simple and robust methodologies are often required. For this narrative review, literature was sourced from scientific databases (primarily PubMed) in the period from June 2022 to January 2024. The regulatory targets of glucose homeostasis that could be modulated by bioactive plant compounds were used as search terms, either alone or in combination with the keyword "root extract". As a result, we present a comprehensive methodological toolbox for studying the glucose homeostasis modulating properties of plant extracts and its constituents. The described assays encompass in-vitro investigations involving enzyme inhibition (α-amylase, α-glucosidase, dipeptidyl peptidase 4), assessment of sodium-dependent glucose transporter 1 activity, and evaluation of glucose transporter 4 translocation. Furthermore, we describe a patch-clamp technique to assess the impact of extracts on KATP channels. While validating in-vitro findings in living organisms is imperative, we introduce two screenable in-vivo models (the hen's egg test and Drosophila melanogaster). Given that evaluation of the bioactivity of plant extracts in rodents and humans represents the current gold standard, we include approaches addressing this aspect. In summary, this review offers a systematic guide for screening plant extracts regarding their influence on key regulatory elements of glucose homeostasis, culminating in the assessment of their potential efficacy in-vivo. Moreover, application of the presented toolbox might contribute to further close the knowledge gap on the precise mechanisms of action of plant-derived compounds.

The Composition and Biochemical Properties of Strophantus (Apocynaceae), with a Focus on S. sarmentosus

The genus Strophantus belongs to the Apocynaceae family of flowering plants which grows primarily in tropical Africa. The plants are widely used in traditional herbal medicine. S. sarmentosus, in particular, is used for the treatment of, e.g., joint pain and rheumatoid arthritis, wound infections, head lice, diarrhea, snake bite, and eye conditions. Despite its widespread use, dedicated research characterizing its bioactive plant components is scarce. Investigations have focused mainly on its cardenolides because of their cardioactivity and historical use as cardiotonic. There are also studies concerning the antibacterial, antioxidant, and anti-inflammatory activity of plant extracts. This review summarizes the present knowledge surrounding the biochemical and analytical research on Strophantus, in general, and S. sarmentosus, in particular, and describes the current state of the field based on the available scientific literature.

Sub-chronic toxicological evaluation of Strophanthus hispidus DC (Apocynaceae) aqueous root extract

OBJECTIVES

Strophanthus hispidus DC (Apocynaceae) has gained wide and extensive applications in herbal medicine in Africa for the treatment of quite a lot of diseases. Owing to the extensive application and the propensity of persistent consumption of this shrub, this research investigates the sub-chronic toxicological effect of aqueous root extract of S. hispidus (SHP) in laboratory animals (rats).

METHODS

The rats were allotted into four groups of eight rats each (n=8) and orally treated daily for ninety (90) days with SHP extract at 100, 500 and 1,000 mg/kg and the control group received distilled water (10 mL/kg). The rats were weighed at 15 days interval. After 90 days daily oral administration of SHP extract, blood samples were collected from the rats into lithium heparin and EDTA bottles for biochemical and haematological analysis respectively. Vital organs were weighed and histological examination was performed on the liver and kidney.

RESULTS

The SHP extract displayed no significant (p>0.05) alterations in body weight of treated compared to control rats. At doses of 500 and 1,000 mg/kg, SHP-treated rats showed significant (p<0.05) increase in white blood cell (WBC), without significant difference in other haematological parameters. Non-significant (p>0.05) decrease in urea and non-significant (p>0.05) increase Na⁺, K⁺ and blood urea nitrogen (BUN) were observed. Significant (p<0.05) decrease in liver weight was observed without any alteration in the architecture of the liver and other organs investigated.

CONCLUSIONS

Aqueous root extract of S. hispidus demonstrated a good safety profile in rats. Therefore, S. hispidus is harmless and safe following sub-chronic oral administration.