"Different Stevia extracts manufactured by Nutramedix®, Now®, Sweet leaf®, and Truvia® were purchased from health food stores in the USA and were labeled randomly as Stevia A, B, C, and D."
"Here, we first evaluated four different commercially obtained Stevia extracts (3 alcohol extracts and one extract in powder form)..."
Nutramedix, Now and Sweet leaf are alcohol extracts but Truvia is a powder form.
Since the labels were randomly assigned, we don't know which is Stevia A but the study says "This might be explained by the reported variations observed in the different phytochemical concentrations of different Stevia extracts, which resulted from the growing conditions and agricultural practices followed..."
So the more concentrated the better?