A quinone methide is a type of conjugated organic compound that contain a cyclohexadiene with a carbonyl and an exocyclic methylidene or extended alkene unit.

Simple unhindered quinone methides are short lived reactive intermediates that are not stable enough to be isolated under normal circumstances, they will trimerise in the absence of nucleophiles.

[3] Quinone methides have been implicated as the ultimate cytotoxins responsible for the effects of such agents as antitumor drugs, antibiotics, and DNA alkylators.

Celastrol is a triterpenoid quinone methide isolated from Tripterygium wilfordii (Thunder of God vine) and Celastrus regelii that exhibits antioxidant (15 times the potency of α-tocopherol),[6] anti-inflammatory,[7] anticancer,[8][9][10][11] and insecticidal [12] activities.

Pristimerin, the methyl ester of celasterol, is a triterpenoid quinone methide isolated from Maytenus heterophylla that displays antitumor and antiviral [13] activities.

[14] Taxodone and its oxidized rearrangement product, taxodione, are diterpenoid quinone methides found in Taxodium distichum (bald cypress), Rosmarinus officinalis (rosemary), several Salvia species and other plants, that display anticancer,[15][16][17] antibacterial,[18][19][20] antioxidant,[21] antifungal,[22] insecticide,[23] and antifeedant [24] activities.