Analgesic and Antidiarrheal Properties of Lappaconitine, Possibly Through Cyclooxygenase and µ-Opioid Receptor...

Lappaconitine (LAP) is a diterpenoid alkaloid with strong anti-inflammatory activity. However, there is limited information on its gastroprotective effects. The present study aimed to explore the analgesic and antidiarrheal effects of LAP through in vivo and in silico studies.

For this, LAP was administered orally to Swiss albino mice at doses of 1 and 4 mg/kg (bw). The analgesic effect was assessed using the acetic acid-induced writhing test. Simultaneously, antidiarrheal activity was evaluated using the castor oil-induced diarrheal secretion test in mice. In addition, an in silico molecular docking analysis was conducted to forecast the participation of cyclooxygenases (COXs) and the µ-opioid receptor.

According to our in vivo findings, LAP and combination therapy (LAP + diclofenac sodium) significantly (p < 0.05) alleviated the number of writhing episodes in the experimental animals compared to the control group. Furthermore, in the castor oil-induced diarrhea model, LAP and combination therapy (LAP + loperamide) significantly (p < 0.05) prolonged the onset time of diarrhea and reduced the number of diarrheal secretions. Besides, the molecular docking study suggested that LAP showed better binding affinity (-8.2 and -7.8 kcal/mol) with COX-1 and COX-2 enzymes, respectively. Likewise, LAP exhibited the highest binding score (-9.8 kcal/mol) with the µ-opioid receptor. Moreover, LAP demonstrated high gastrointestinal absorption with low toxicity.

Therefore, LAP exerts potential analgesic and antidiarrheal effects, as well as synergistic properties with diclofenac sodium and loperamide through the cyclooxygenase and MOR interaction pathways.