resin

A mixture of high-molecular-weight compounds, mainly polymerized acids, esters, and terpenoids, exuded by certain plants particularly when wounded. Resins are insoluble in water but soluble in ethanol. On exposure to air the volatile components evaporate leaving a solid or semisolid residue protecting the damaged area. Resins are particularly prevalent in conifers, which contain  specialized   *resin canals.   Pine resin yields the essential oil turpentine (C₁₀H₁₆) on distillation and the solid residue rosin, used in lacquers. Other commercially important resins are dammar (from trees of the genera Shorea and Agathis), kauri (from the New Zealand conifer Agathis australis), jalap (from the Mexican convolvulaceous plant Exogonium purga), and mastic (from the evergreen anacardiaceous tree Pistacia lentiscus). Semisolid mixtures of resins and essential oils are often termed balsams and include Canada balsam from Abies balsamea and frankincense from species of Boswellia.