Abstract
(+)-Nootkatone (NTK) is a bioactive sesquiterpene with significant therapeutic potential, but its application is hindered by low aqueous solubility and physical instability. Inclusion complexation with βcyclodextrin (βCD) offers an effective strategy to overcome these biopharmaceutical limitations. The present study investigated the antinociceptive effects of isolated nootkatone and its β-cyclodextrin inclusion complex (NTK/βCD) in murine models of acute nociception. The NYK/βCD complex was obtained by solvent co-evaporation method, and the drug content was quantified at 43.37% by GC-FID. Animals received NTK and NTK/βCD orally at 10 mg/kg. Central nervous system (CNS) effects were assessed using the rotarod and open-field tests, while antinociceptive activity was evaluated through the acetic acid-induced abdominal writhing test (1% acetic acid) and the formalin test (2.5% formalin). Additional assessment of antinociceptive effects was conducted using the hot plate and tail-flick tests. To elucidate the involvement of specific pain-signaling pathways, the opioid, nitric oxide, vanilloid, glutamatergic, cyclic guanosine monophosphate (cGMP), α1- and α2-adrenergic, dopaminergic, and serotonergic pathways were examined. Administration of NTK and NTK/βCD (10 mg/kg) did not produce significant effects on the CNS. In the acetic acid-induced abdominal writhing test, NTK and NTK/βCD reduced the number of writhes by 90.21% and 84.78%, respectively. In the formalin test, reductions of 51.81% and 47.58% were observed during the first phase, while reductions of 81.82% and 74.29% were observed during the second phase. In the hot plate test, NTK and NTK/βCD increased response latency by 116.72% and 121.66%, respectively. In the tail-flick test, response latency increased by 79.87% and 100.55%, respectively. Crucially, as NTK/βCD exhibited a drug content of 43.37%, the 10 mg/kg dose supplied an effective active payload of only 4.34 mg/kg and showed antinociceptive efficacy statistically equivalent to 10 mg/kg of uncomplexed NTK. The findings indicate that NTK and NTK/βCD may exert antinociceptive effects through the opioid, nitric oxide, vanilloid, glutamatergic, cGMP, and α2-adrenergic signaling pathways. Collectively these results demonstrate that that NTK and NTK/βCD possess significant antinociceptive potential and that β-cyclodextrin inclusion significantly enhances the dose efficiency of nootkatone, enabling equivalent pain management at less than half the active ingredient dose, rendering them promising candidates for the development of alternative therapeutic strategies for pain management.