Preparation of Oral Emulsion of Valeriana officinalis Hydro-Alcoholic Extract and Comparison of its Analgesic and Anti-Anxiety Effects with Valerian Extract in Adult Male Wistar Rats

Chronic neuropathic pain is one of the common and debilitating problems of human societies and is a challenge in health care Valerian officinalis has been used in the treatment of pain and anxiety due to its antioxidant effects and multiple mechanisms. Also, the medicinal form of emulsion is studied to increase the bioavailability and absorption of herbal products. The present study was conducted to determine the analgesic and anti-anxiety effects of the oral emulsion of the extract and compare it with the effects of the extract in adult male rats. First, the oral emulsion of the extract was formulated with the help of similar studies and Design Expert software, and the best formulation was selected. Then, neuropathic pain was induced in the animals with the help of a sciatic nerve chronic obstructive lesion (CCI) neuropathy surgical model. The extract and emulsion were given orally (gastric gavage) to the animals for 30 days, after which behavioral tests were performed, to investigate thermal allodynia, and elevated plus maze (EPM), to investigate induced anxiety behaviors, one day before Induction of neuropathy and on days 2, 4, 6, 10, 14, 21, 30 after neuropathy were investigated, and at the end, the effects of oral emulsion gavage of extract and extract on lipid peroxidation of malondialdehyde (MDA) in brain tissue were investigated and compared. Separate administration of valerian extract and emulsion reduced cold allodynia in all days after CCI surgery compared to the neuropathy group (P<0.05). In addition, CCI surgery caused anxiety in rats. Administration of valerian emulsion and its extract were able to significantly reduce anxiety in the behavioral test of the plus-shaped elevated maze. The difference is that this reduction process started earlier with the administration of the extract emulsion (P<0.001). Also, the administration of the extract and emulsion significantly reduced the amount of malondialdehyde in the brain tissue in neuropathic rats compared to the neuropathy group (P<0.001), with the difference that the emulsion of the extract caused a greater decrease in the amount of malondialdehyde compared to the extract. Valerian extract and emulsion have analgesic and anti-anxiety effects. In addition, the administration of valerian emulsion in neuropathic rats has significantly more anti-anxiety and analgesic effects compared to the administration of valerian extract.