Salvadoraceae

A very small family — three genera and a handful of species — of shrubs and small trees native to the arid and semi-arid regions of Africa, Arabia and South Asia. Its medicinal member here is miswak (Salvadora persica), the arak or toothbrush tree, whose root and stem are cut into chewing sticks.

The family’s chemistry is what makes it interesting. Despite no close relationship to the cabbage family, its members store glucosinolates and release pungent isothiocyanates — chiefly benzyl isothiocyanate — on chewing or crushing, the same reaction that gives mustard its heat. That antimicrobial chemistry, delivered mechanically by the brush of separated fibres, is the basis of miswak’s use in oral hygiene.