Contribution of spathulenol to the anti-nociceptive effects ofPsidium guineense

Objectives:Araca-verdadeiro is the popular name ofPsidium guineense(Myrtaceae), whose fruits and leaves are used in Brazilian folk medicine for treatment of inflammation and pain. The focus of the present research was an investigation of the anti-nociceptive, and anti-inflammatory effects of the essential oil fromP. guineense(EOPG) leaves, and of spathulenol. The anxiolytic and antidepressive effects associated with chronic pain were also investigated in models of acute or persistent nociception or/and inflammatory pain. Methods and Results:Oral treatment with EOPG (10-100 mg/kg) or spathulenol (10 mg/kg) significantly inhibited formalin-induced nociceptive responses, both sensitivity to cold and edema. Oral treatment with EOPG (10 mg/kg) and spathulenol (10 mg/kg) did not reduce locomotor activity (open field test). Local administration of spathulenol (1000 mu g/paw) significantly prevented formalin-induced nociceptive sensitivity to cold and paw edema, and carrageenan-induced mechanical hyperalgesia, paw edema and sensitivity to cold. In the Freund's complete adjuvant (CFA) model, oral treatment with EOPG (10 mg/kg) or spathulenol (10 mg/kg) for 21 days significantly inhibited all analyzed parameters. The percentage maximal inhibition by spathulenol was 76.00% (mechanical hyperalgesia), 71.90% (cold response), 85.00% (edema), 77.16% (myeloperoxidase activity), 97.72% (time in the closed arms in the elevated plus maze), and 49.00% (immobility time in the tail suspension test), in the CFA model. Models employed maleSwissmice, except for the CFA test, which employed C57bL6 male mice (n=6 /group). Conclusion:This study demonstrates that EOPG is an anti-nociceptive and anti-hyperalgesic agent, in acute and continuous treatment, and an anxiolytic and antidepressive agent when tested with the chronic pain experimental state.

Automated summary

This study demonstrates that the essential oil from Psidium guineense leaves has anti-nociceptive and anti-hyperalgesic effects in acute and continuous treatment, and exhibits anxiolytic and antidepressive effects in the experimental state of chronic pain.