Stevioside is a glycoside derived from the stevia plant, which can be used as a sweetener.
Metabolism
When ingested by humans, the main metabolite is steviol glucuronide (also known as steviol 19-O-beta-D-glucopyranosiduronic acid).[1] Stevioside is first metabolized to steviol and then to steviol glucuronide.
Glucuronidation to steviol glucuronide was primarily mediated by UGT2B7 at low concentration and UGT2B7 and UGT1A3 at high concentration as determined by in vitro tests using liver and intestinal microsomes of both humans and rats.[2]
Effects on Enzymes
It is suggested that stevioside could potentially be used as a competitive inhibitor of UGT2B7. In humans, stevioside is primarily metabolized into steviol glucuronide.[1] With UGT2B7 being shown in vitro to be the primarily human enzyme responsible for steveioside being metabolized into steviol glucuronide[2], it might be possible to use large doses of stevioside to use up most of the available UGT2B7 enzymes, allowing other UGT2B7 substrates to avoid metabolism by UGT2B7. The potential ability of stevioside to function as a competitive inhibitor of UGT2B7 has not been verified clinically in human subjects.
Effects on Learning and Memory
Stevioside appears to help prevent memory loss. In one study using rats, pretreatment of stevioside (250 mg/kg dose orally) significantly reversed scopolamine-induced learning and memory deficits. Stevioside also reduced scopolamine-induced rise in brain AChE activity and brain oxidative stress levels.[3]