Background:
Neuropathic pain is one of the contributors to the global burdens of illness. At present many patients do not achieve satisfactory pain relief even with synthetic pain-killers. Taking this into consideration, it is necessary to
search for natural product-derived alternative treatment with confirmed safety and efficacy. Ageratum conyzoides L is a
plant often used as analgesic in Indonesia, however, anti-neuropathic pain activity of this plant is still unknown.
Objective:
To determine the anti-neuropathic pain activity of the essential oil and non-essential oil component (distillation
residue) of A. conyzoides L.
Methods:
We conducted separation of the essential oil component from other secondary metabolites through steam distillation. Both components were tested for anti-neuropathic pain activity using chronic constriction injury animal models with
thermal hyperalgesia and allodynia tests. The animals were divided into 7 test groups namely normal, sham, negative, positive (pregabalin at 0.195 mg/20 g BW of mice), essential oil component (100 mg/kg BW), and non-essential oil component
(100 mg/kg BW). Naloxone was tested against the most potent anti-neuropathic pain component (essential oil or nonessential oil) to investigate the involvement of opioid receptor.
Results:
The GC-MS of the essential oil component indicated the presence of 60 compounds. Meanwhile, non-essential oil
components contained alkaloid, flavonoid, polyphenol, quinone, steroid, and triterpenoid. This non-essential oil component
contained a total flavonoid equivalent to 248.89 ppm quercetin. The anti-neuropathic pain activity test showed significantly
higher activity of the essential oil component compared to the non-essential oil component and negative groups (p<0.05).
Furthermore, the essential oil component showed equal activity to pregabalin (p>0.05). However, this activity was abolished
by naloxone, indicating the involvement of opioid receptor in the action of the essential oil component.
Conclusion:
The essential oil component of A. conyzoides L is a potential novel substance for use as anti-neuropathic pain.
Alterations in the rostral ventromedial medulla after the selective ablation of μ-opioid receptor expressing neurons
