Analgesic Effect Of Wild Papaya Extract

Stauntonia chinensis DC.is a kind of plant amedicas of important medicinal values.It had many pharmacological effects,such as analgesia,anti-inflammatory,nerve blocking, radiosensitization and so on.In addition,it has been widely applied for the treatment of rheumatism arthralgia.However,up to date,there is no report about the thorough study of the analgesic effect and mechanism of extracts of Stauntonia chinensis.Therefore,the present research is focused on studying the analgesic activity of vine-stem extract(YMG),the water extract of YMG(YMGW)and ethanolic extract of YMG(YMGB)and the fractions(YMGB1, YMGB2,YMGB3,YMGB4,YMGB5,YMGB6 and YMGB7)by quantifying pain with several experimental animal models,and the possible analgesic mechanism of the effective fractions, with the aim to provide a scientific experimental basis for clinical development and further research of Stauntonia chinensis.Firstly,the present research evaluated the analgesic activity of a series of extracts of Stauntonia chinensis by constructing three experimental animal pain models.The results of the acetic acid-induced writhing behaviour in mice showed when compared with the control group, YMGW,YMGB,YMGB1,YMGB3,YMGB4,YMGB6 and YMGB7 at 500 mg/kg can significantly reduce the writhing numbers,they had peripheral analgesic activity,and their analgesic effects were comparable with aspirin.YMGB and YMGB6 at 500 mg/kg had no analgesic effect on hot plate-induced mouse licking postpedes.The results of the formalin test showed YMG,YMGW,YMGB1,YMGB3 and YMGB5 at 400 mg/kg had peripheral analgesic activity,and YMGB6 and YMGB7 had a significant anti-inflammatory activity.In conclusion, all fractions extracted from Stauntonia chinensis had peripheral other than central anagesic activity,except YMGB2.Secondly,the quantitative dose-activity relation and the quantitative time-activity relation were evaluated for the above effective extracts in both acetic acid-induced writhing and formalin test.The analgesic effects were dose-dependent for YMG,YMGW,YMGB1,YMGB4,YMGB5,YMGB6 and YMGB7.The biggest analgesic effect appeared after 45 min when YMGB6 was dosed at 500 mg/kg.The mechanism of the analgesic effect of extracts of Stauntonia chinensis is not related to opioid receptor because Naloxone,a morphine receptor antagonist,can significantly inhibit the analgesic effect of morphine,and the corresponding possible maximum analgesia percent (PMAP)was reduced by 57%,but it was not effective for YMGW and YMGB's PMAP.In HT-29 cell model,whether the analgesic effect was associated with the activity of COX-2 and the formation and release of PGE₂ were evaluated.The result showed YMGW and YMGB5 took the analgesic effect by reducing the expression level and activity of COX-2.YMGB,YMGB4, YMGB6 and YMGB7 took effects by inhibiting the activity of COX-2 and the formation and release of PGE₂.In conclusion,YMG,YMGW,YMGB and YMGB1-7 except YMGB2 had peripheral analgesic activity.Their analgesic and anti-inflammatory effects were dose-dependent,and the effective time of analgesia was about 1h.They took effect by reducing the expression level and the activity of COX-2 and then inhibiting the formation and release of PGE₂.