Study of the pharmacokinetics of eriodictyol-6-C-β-d-glucoside, a flavonoid of rooibos (Aspalathus linearis) extract, after its oral administration in mice.

Systemic dry syndrome affects quality of life, and various effective methods are being developed for its treatment. We recently found that rooibos (Aspalathus linearis) extract activates muscarinic M3 receptor and improves dryness in mice and humans. We identified eriodictyol-6-C-β-D-glucoside (E6CG) as the active component affecting the secretory functions of exocrine glands; however, the pharmacokinetics and distribution of E6CG in exocrine glands have not been elucidated in mice receiving rooibos extract. We have developed a quantification method using LC-MS/MS to detect E6CG without an internal standard. Experiments on C57BL/6 mice administered rooibos extract showed that E6CG was transferred into blood plasma, with its concentration levels peaking 19.3 min after treatment. Substantial levels of E6CG were detected in the submandibular, sublingual, parotid, and lacrimal glands and in the sweat glands in palm skin. This study reports that rooibos extracts containing E6CG can be used as functional foods for improving systemic dryness.