Chemical composition, acute toxicity, and antinociceptive activity of the essential oil of a plant breeding cultivar of basil (Ocimum basilicum L.).

Ocimum basilicum L. is an aromatic herb used in Brazil to treat illnesses such as respiratory and rheumatic problems, vomiting, and pain. In the present study, the chemical composition, acute toxicity, and antinociceptive effects of the essential oil (EO) of the cultivar "Maria Bonita" obtained from O. basilicum L. PI 197442 genotype were evaluated in Swiss mice (20-35 g each). Lethal dose to cause 50 % death (LD50) was calculated from a dose-response curve (100-5000 mg/kg body wt.; n = 6) as 532 mg/kg body wt. In the acetic acid-induced writhing test (0.6 % i. p.), EO (50, 100, and 200 mg/kg body wt., n = 8, s. c.) was effective in reducing the abdominal contractions at all doses (48-78 %). In the hot-plate test, EO significantly increased the latency at 50 mg/kg body wt. at all times (37-52 %, n = 8, s. c.). However, the effects of morphine and EO at 50 mg/kg were reverted in the presence of naloxone, an opioid antagonist. In the formalin test, EO significantly reduced paw licking time in the first and second phases of pain at 200 mg/kg body wt. (38 and 75 %, respectively, n = 8, s. c.). The results suggested that the peripheral and central antinociceptive effects of EO are related to the inhibition of the biosynthesis of pain mediators, such as prostaglandins and prostacyclins, and its ability to interact with opioid receptors.