Antinociceptive Effect of the Citrus Flavonoid Eriocitrinon Postoperative Pain Conditions

BACKGROUND

Postoperative pain remains a major clinical problem as there are limited analgesic strategies that have been proven to be effective in preventing and relieving this type of pain. Natural products, including flavonoids, have distinct pharmacological properties and play an important role in the discovery of analgesic drugs.

MATERIALS AND METHODS

In this study, the flavonoid eriocitrin (eriodictyol 7-O-rutinoside), which is the main flavonoid in lemon fruit (Citrus limon), was mechanistically investigated for its prospective antinociceptive effect in a mouse model of postoperative pain. The antinociceptive property was evaluated by utilizing both tonic (acetic acid-induced writhing behavior) and phasic (hot-plate) nociception modalities. The hindpaw incisional surgery was performed and hyperalgesia was assessed using von Frey filaments.

RESULTS

The tested doses of eriocitrin significantly attenuated (P<0.01, P<0.001) the chemically-induced tonic visceral nociception (5, 10, 15, and 30 mg/kg) and acute phasic thermal nociception (10, 15, and 30 mg/kg). A significant dose-dependent reduction in the incisional nociceptive hyperalgesia was exhibited by eriocitrin, with a marked antinociception observed at doses of 15 mg/kg (P<0.05 during 30-60 minutes) and 30 mg/kg (P<0.05, P<0.01 during 30-120 minutes).

CONCLUSION

The antinociceptive effect of eriocitrin (30 mg/kg) was strongly blocked by the antagonists of the opioid receptor, naltrexone, and GABAA receptor, bicuculline, thereby suggesting the involvement of opioidergic and GABAergic mechanisms in the nociception, reducing proclivity of eriocitrin during transmission of incisional nociception. These results concluded that eriocitrin has a potent antinociceptive effect in postoperative pain conditions, probably mediated through opioid and GABAA receptors.

Dietary dehydrated lemon peel improves the immune but not the antioxidant status of gilthead seabream (Sparus aurata L.)

Lemon (Citrus limon) is the third most important species of citrus in the world, while Spain is the major producer in Europe. Numerous beneficial effects of lemon are known, which explains their use in traditional medicine. The paper describes the effect of dietary dehydrated lemon peel (a sub-product of the lemon industry) on the growth, immune and antioxidant status of gilthead seabream (Sparus aurata L.) over a period of 30 days. Fish fed diets enriched with dehydrated lemon peel (1.5% and 3%) for 15 days showed improved growth and both humoral (seric immunoglobulin M) and cellular (peroxidase activity and phagocytic ability of head kidney leucocytes) immunity, as well as the expression of some immune-related genes (nkefa, il1β, igth and csfr1). However, decreases growth promotion was observed after thirty days of trial. Neither the anti-oxidant enzymes activity nor the expression of several anti-oxidants and anti-stress genes in liver was improved by the diet. The possible inclusion of dehydrated lemon peel in fish diets for its immunostimulant effects is discussed.