Anti-inflammatory and toxicological evaluation of essential oil from Piper glabratum leaves.

ETHNOPHARMACOLOGICAL RELEVANCE: Although some of the species of the genus Piper exhibit interesting biological properties, studies on Piper glabratum Kunth are very limited. AIM OF THE STUDY: This study investigated the anti-inflammatory activity and the toxicological profile of the essential oil from P. glabratum leaves (OEPG) in mice. MATERIALS AND METHODS: The acute toxicity of OEPG was evaluated by oral administration to female mice as single doses of 500, 1000, 2000 or 5000mg/kg/body weight. In the subacute toxicity test, the females received 500 or 1000mg/kg/body weight of OEPG for 28 days. The anti-inflammatory potential of OEPG was evaluated using four models including pleurisy, edema, mechanical hyperalgesia and cold allodynia models in mouse paws. RESULTS: No clinical signs of toxicity were observed in animals after acute treatment, which suggested that the LD50 is greater than 5000mg/kg. The subacute exposure to OEPG produced no significant changes in the hematological or biochemical parameters. Similarly, the histology of the organs and the estrus cycle displayed no marked alterations. OEPG exhibited anti-inflammatory activity as indicated by inhibition of the leukocyte migration (100, 300, 700mg/kg) and the protein extravasation into the pleural exudates (700mg/kg). After intraplantar injection of carrageenan, it was observed that the 700mg/kg dose of OEPG reduced edema formation and decreased the sensitivity to mechanical stimulation and cold. CONCLUSIONS: These results demonstrate the anti-inflammatory potential of the essential oil of P. glabratum leaves in the absence of toxicity in female mice.

Anti-nociceptive, anti-hyperalgesic and anti-arthritic activity of amides and extract obtained from Piper amalago in rodents.

ETHNOPHARMACOLOGICAL RELEVANCE: Piper amalago (Piperaceae) has been used in folk medicine as an analgesic. This study aimed to evaluate the pharmacological effects of extract and pure amides obtained from P. amalago on pain to provide a pharmacological basis for their use in traditional medicine. AIM OF THE STUDY: This study evaluated the anti-nociceptive, anti-hyperalgesic, anti-arthritic and anti-depressive activities of the ethanolic extract of P. amalago (EEPA) and the amides N-[7-(3',4'-methylenedioxyphenyl)-2(Z),4(Z)-heptadienoyl] pyrrolidine (1) and N-[7-(3',4'-methylenedioxyphenyl)-2(E),4(E)-heptadienoyl] pyrrolidine (2) obtained from P. amalago in animal models. MATERIALS AND METHODS: Mice treated daily with EEPA (100mg/kg, p.o.) were assayed for 20 days for knee edema (micrometer measurement), mechanical hyperalgesia (analgesiometer analysis), heat sensitivity and immobility (forced swim test) in the Complete Freund's Adjuvant (CFA) model. Cold (acetone test) and mechanical hyperalgesia (electronic von Frey analysis) responses were evaluated for 15 days in rats treated with oral EEPA (100mg/kg) in the spared nerve injury (SNI) model. Meanwhile, mice were evaluated for carrageenan-induced edema and mechanical hyperalgesia and for nociception using the formalin model after a single administration of EEPA (100mg/kg) or amides 1 and 2 (1mg/kg). RESULTS: Amides (1) and (2) were detected and isolated from the EEPA. The EEPA inhibited mechanical hyperalgesia, knee edema, and heat hyperalgesia, but not depressive-like behavior, induced by the intraplantar injection of CFA. When evaluated in the SNI model, the EEPA inhibited mechanical and cold hyperalgesia. The EEPA, 1 and 2 prevented the mechanical hyperalgesia induced by carrageenan and the anti-nociceptive effects in both phases of formalin nociception. The EEPA did not induce alterations in the open field test. CONCLUSION: The EEPA was effective for inhibition of pain and arthritic parameters but was not effective against depressive-like behavior; additionally, it did not alter locomotor activity. The amides obtained seemed to be the active component(s) present in the EEPA because they proved to be anti-nociceptive and anti-hyperalgesic in models of acute pain. Considering that few drugs are currently available for the treatment of chronic pain, especially neuropathic pain, the present results may have clinical relevance and open new possibilities for the development of new anti-hyperalgesic and anti-arthritic agents from P. amalago.

Differential vascular adaptive response to stress exposure in male and female rats: role of gonadal hormones and endothelial cells.

UNLABELLED: Although there are reports concerning a vascular adaptive response to stress in males, this is not yet defined in females. The aim of this study was to delineate functional gender differences in the rat vascular adaptive response to stress and to determine the ability of sex hormones to modulate the stress-induced vascular adaptive response. Responses to noradrenaline were evaluated in aortas, with and without endothelium, from intact, gonadectomized and gonadectomized-hormone-replaced males and females submitted or not to stress (2-h immobilization). Reactivity of the aorta of stressed and non-stressed intact males and females (n = 6-14 per group) was also examined in the presence of L-NAME or indomethacin. Stress decreased and gonadectomy increased maximal responses to noradrenaline in aortas with intact endothelium from both genders. Stress also reduced noradrenaline potency in males. In females, but not males, stress decreased the gonadectomy-induced noradrenaline hyper-reactivity to near that of intact non-stressed rats. Hormone replacement restored the gonadectomy-induced impaired vascular adaptive response to stress. L-NAME, but not indomethacin, abolished the stress-induced decrease in aorta reactivity of males and females. None of the procedures altered reactivity of aortas denuded of endothelium. CONCLUSION: Stress-induced vascular adaptive responses show gender differences. The magnitude of the adaptive response is dependent on testicular hormones and involves endothelial nitric oxide-system hyperactivity.