From scent to saliva: The saliva-stimulating effect of terpenes in dry mouth

Objectives: There is an increasing trend towards the use of bioactive compounds in oral healthcare. Some have been identified as sialagogues, such as mastic resin and its main isolate, α-pinene. These act as acetylcholinesterase inhibitors (AChEIs), consequently increasing salivary flow. With up to half of the global population experiencing dry mouth symptoms, there is a clear need for new interventions. Design: An in vitro screening of a 148-compound library was conducted to identify novel AChEIs. Following this, four compounds were chosen for an in vivo validation and were administered through nasal spray pumps to act as an olfactory stimulus in healthy individuals (n = 12) to evaluate their sialagogic effects. Saliva quantity, rheology, and composition (total protein concentration and MUC5B concentration) were analysed before and after the use of the compounds. Results: This study confirmed α-pinene, and identified basil, eugenol and guaiacol as AChEIs in vitro. Basil and guaiacol significantly increased salivary flow, while simultaneously basil preserved the spinnbarkeit levels. α-Pinene, basil and guaiacol increased the subjective feeling of moistness of the mouth. Total salivary protein concentration was not affected by scent of these compounds, however, α-pinene, basil and guaiacol significantly increased MUC5B output. Furthermore, basil was found to have the most pleasant scent out of the four compounds. Conclusions: In conclusion, this study showed the potency of basil and guaiacol as novel sialagogues. However, further research is necessary to assess the long-term effects and efficacy in patients diagnosed with dry mouth.