Host–guest inclusion complexation of β-cyclodextrin and hecogenin acetate to enhance anti-hyperalgesic effect in an animal model of musculoskeletal pain

Abstract Hecogenin acetate (HA), a steroidal acetylated-sapogenin, has an analgesic profile already assigned, but its low water solubility and short half-life limit its use in chronic conditions. β-cyclodextrin (β-CD) can improve the chemical and pharmacological property of nonpolar compounds such as HA. Therefore, a HA complexed with β-CD (HA-CD) was prepared and characterized by thermal, morphological and spectroscopic analysis. A model of chronic musculoskeletal pain was induced by means of two injections of pH 4.0 saline (20 μL) into the left gastrocnemius 5 days apart was used. After confirming hyperalgesia, male mice were treated with HA, HA-CD (20 mg/kg; p.o.) or vehicle (saline 0.9%, p.o.). Motor coordination tests, substance P (SP) levels in a lumbosacral (L4-S2) spinal cord sample and a docking study were equally assessed to check for a possible action on the opioid receptors. Oral pretreatment with HA or HA-CD produced a significant antinociceptive (p