Terpenoids Isolated from Psidium guajava Hexane Extract with Depressant Activity on Central Nervous System

A bioguided fractionation of the hexane extract obtained from Psidium guajava leaves led to the isolation of sesquiterpenes with depressant activities on the central nervous system. The results demonstrated that the already reported relaxant properties of Psidium guajava hexane extract are largely due to the presence of terpenes, especially caryophyllene-oxide and β-selinene, which were by far the largest single components and potentiated pentobarbital sleeping time and the latency of convulsions induced by leptazol in mice. Calcium concentration-response curves showed a rightward displacement when the active fraction was added to isolated guinea-pig ileum depolarized with K⁺ (60 mm) and cumulative concentrations of CaCl₂, suggesting that caryophyllene-oxide, a known Ca²⁺ antagonist agent could be responsible for the blockade of extracellular Ca²⁺ observed with the active fraction.