Fluoride content in khat (Catha edulis) chewing leaves.

Khat (qat) leaves are chewed for their psychostimulative effects; there is an unconfirmed suggestion that they contain a high concentration of fluoride (F). Khat samples from Yemen were suspended in deionized water, spun, and the supernatants exposed to a chelator that decomplexes F, which was assayed with an F(-)-electrode coupled to an ion analyser. F released into whole saliva after chewing khat for 15 min and from khat suspended in stimulated whole saliva for 1.5 h in vitro was measured also. Total F in dried khat leaves and their ash was assayed by the acid-hexamethyldisiloxane microdiffusion method. All methods demonstrated negligible amounts of F in or from khat leaves (<0.02 microg F/ml leached into water or saliva; 0.06 microg F/ml in saliva after chewing; 0.93 microg total F/g in dried leaf, 2.07 microg total F/g in ash).