Novel effects of rooibos extract on tear and saliva secretion mediated by the muscarinic acetylcholine receptor 3 in mice.

Objectives: Sicca syndrome is characterized by dry mouth and eyes and results in a reduction of the patient's quality of life. Various natural plants, including certain herbs, have long been employed to alleviate such symptoms. Rooibos grown in South Africa is one of the potent herbal plants used for the treating dry mouth. However, the precise mechanism of action by which rooibos alleviates symptoms of dryness remains unclear.

Methods: The in vivo effects of rooibos extract (RE), which comprises eriodictyol-6-C-glucoside, on the secretory function of saliva and tears were analyzed after intraoral RE administration using wild-type C57BL/6 (B6) mice. In addition, the mechanisms of RE were investigated after administration of a muscarinic acetylcholine receptor 3 (M3R) antagonist.

Results: Tear and saliva volumes in mice increased significantly and in a dose-dependent manner following intraoral RE administration compared to those in mice in the control group administered HO. An experiment performed using darifenacin administration revealed that the effects of RE on secretory function were exerted via M3R.

Conclusion: These results suggest that RE administration is an effective treatment for symptoms of dryness and may be used in clinical settings against sicca syndrome.