Isosteviol

Stevia rebaudiana is a popular plant-derived noncaloric sweetener with numerous health benefits. The steviol glycosides (SGs) are regarded as primary sweetening components of this plant, having diverse flavour profiles and individual significance. Numerous ongoing research studies focusing on enhancing specific SGs' yields, improving sweetness, and reducing bitter aftertaste require a simple and efficient method involving SG precursors and as many of its glycosides in one go. The simultaneous analysis of SG precursors (steviol and isosteviol) and its glycosides are vital to ensure the quality, safety, and regulatory compliance of stevia-based products. This highlights the need for the development of an easy, reliable, and efficient method involving as many SGs and its precursors in one go. With this aim, a UPLC-PDA based method was developed involving fifteen key SGs along with their precursors steviol and isosteviol, which is the first report having both precursors and fifteen SGs in a single analytical run. The developed method was validated by incorporating numerous parameters such as linearity, accuracy, precision, sensitivity, specificity, peak resolution, peak asymmetry, theoretical plate numbers, peak height/area ratio, peak kurtosis, and peak skew. The developed method represents excellent linearity having regression coefficients (r²) value ranging from 0.998 to 0.999. The detection and quantification limits were 0.18-3.60 μg/mL and 0.60-12.00 μg/mL, respectively, indicating sensitivity for low-concentration analysis. Recovery values ranged from 94.45 % to 102.10 %, confirming the accuracy of method. The intra-day and inter-day precision, evaluated through RSD values for both peak area and retention time, also remained within acceptable limits. Overall method was found in accordance with ICH guidelines, having symmetric, well-resolved peaks with improved sensitivity and theoretical peak count numbers. The developed method was applied to plant extract and stevia-based market products, including tablets, sachets, liquid drops, and powder, to showcase the developed method's efficacy in estimating metabolites in diverse sample matrices.

Presently, numerous studies are exploring the cardioprotective effects of compounds derived from native plants. In particular, research suggests that isosteviol may exert potential cardioprotective effects, linked to Protein Kinase B (Akt) activation. This study aimed to explore the role of Akt and GSK-3β in the cardioprotective effects mediated by the acute administration of isosteviol in Langendorff-perfused female rat hearts subjected to ischemia-reperfusion (Is-Rs). Hearts from female Wistar rats were subjected to Is-Rs. Isosteviol (5 µM) was added to the perfusate 10 min before ischemia. Wortmannin, a phosphatidylinositol 3-kinase (PI3K)/Akt inhibitor (100 nM), was added 15 min before ischemia. Mitochondrial ultrastructure was analyzed by electron microscopy, and the phosphorylation profile of Akt and GSK-3β were studied by western blot. Effects on mitochondrial permeability transition pore (MPTP) opening was assessed via calcium retention capacity (CRC). Docking studies using AutoDock4-Bias were performed to explore potential interactions between isosteviol and Akt or GSK-3β. ANOVA, n=6/group. Isosteviol improved cardiac post-ischemic mechanical recovery and reduced infarct size. It also increased the phosphorylation of Akt and GSK-3β after Is-Rs. Isosteviol treatment prevented MPTP opening, evidenced by the increase in CRC, and preserved mitochondria structure from the expected deterioration toward the end of Is-Rs protocol. All these beneficial effects were prevented, at least in part, by wortmannin. Finally, the results showed that isosteviol interacted with favorable binding energies at the phosphoinositide-binding site of Akt and the kinase site of GSK-3β. These results suggest that cardioprotective effects of isosteviol could be partly mediated by Akt activation, GSK-3β phosphorylation and the inhibition of MPTP opening.