Analgesic activity of Costus igneus and identification of candidate bioactive constituents.

Abstract

Abstract: This study investigated the analgesic activity of Costus igneus and sought to identify candidate phytochemical constituents associated with the observed biological activity through combined computational and experimental evaluation. Chemical profiling identified 160 putative constituents from the 70% methanolic leaf extract, from which eighteen compounds were prioritized following pharmacokinetic and toxicity screening. Comparative molecular interaction analysis highlighted two compounds, 5,8-dimethyl-1,4,6,7-tetrahydronaphthalene-1 (CI11) and R-limonene (CI14), for further characterization. Among the prioritized candidates, CI11 showed comparatively consistent interaction patterns across pain-related targets. Docking scores reached - 6.3 kcal mol^-1 against cyclooxygenase-1, - 6.9 kcal mol^-1 against cyclooxygenase-2, and - 7.5 kcal mol^-1 against the µ-opioid receptor, values approaching those of the corresponding reference compounds within each target system. Interaction analysis suggested contributions from both hydrogen bonding and hydrophobic stabilization, including contacts with residues CYS36 and ASN34 in cyclooxygenase-1, GLN396, ASP393, and THR394 in cyclooxygenase-2, and TYR148 within the µ-opioid receptor model. R-limonene displayed a more hydrophobic interaction profile and generally lower binding performance. DFT predicted spectroscopic and electronic characterization of CI11 and CI14 was performed after docking-based prioritization to examine structural features associated with interaction behavior. In vivo evaluation using the acetic acid-induced writhing model demonstrated significant analgesic activity of the extract, producing 48.8% inhibition at 300 mg kg^-1 (p < 0.001). Viewed in context, the findings identify CI11 as a candidate bioactive constituent and suggest that the analgesic activity of Costus igneus may involve multiple nociception-related pathways, although compound-specific and mechanistic validation remains necessary.

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