These data show for the first time that EOPs has a significant and peripheral antinociceptive effect that seems unrelated to interaction with the opioid system. EOPs also displays a significant anti-inflammatory effect in acute inflammation models. This effect seems to be related to components which inhibit the production of several inflammatory mediators. These results support the widespread use of Peperomia serpens in popular medicine to treat inflammation and pain.

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The antinociceptive and antispasmodic properties of the essential oil of OCIMUM micranthum (EOOM) were characterized. In mice, EOOM (15-100 mg · kg (-1), p. o.) reduced both the writhing responses induced by acetic acid and the licking-time induced by formalin, being inert on the hot plate test. In rat trachea, EOOM relaxed sustained contractions induced by KCl or carbachol (CCh). Its constituents, ( E)- [( E)-MC] and ( Z)-methyl cinnamate [( Z)-MC], reproduced several effects of EOOM. Inhaled as aerosol, EOOM prevented tracheal hyperresponsiveness to KCl or CCh in ovalbumin-sensitized animals after antigen challenge. Thus, EOOM exerts peripheral analgesia in nociception of inflammatory origin and has antispasmodic actions on rat airways under an inflammatory environment. Its effects are mainly due to ( E)-MC, which makes this substance potentially interesting for studies involving conjunctly smooth muscle cells, nociception, and inflammation. Other EOOM constituents also appear to be involved in its pharmacological actions.

In this study, 1-nitro-2-phenylethane was evaluated with respect to its effects in edema models of acute inflammation induced with carrageenan, dextran, and croton oil. 1-Nitro-2-phenylethane produced inhibition of rat paw edema induced by carrageenan and dextran at the doses of 25 and 50 mg/kg. The same doses caused an inhibition of croton oil-induced ear edema in mice. Our results suggest that 1-nitro-2-phenylethane has anti-inflammatory activity, probably of peripheral origin, acting in the synthesis and/or release of inflammatory mediators. A conformational study of 1-nitro-2-phenylethane was carried out using density functional theory calculations, showing three different groups of conformers corresponding to energy minimum geometries. The stereoelectronic repulsions are responsible for conformational preferences and the one most stable conformer. The prostaglandin endoperoxide synthase mechanism is related more to electrophilic than nucleophilic properties.

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