Background/Objectives: Annona squamosa is used in folk medicine to treat pain and arthritis. Palmatine is an alkaloid isolated from several plants, including A. squamosa leaves. The aim of the present study was to investigate the analgesic, anti-arthritic, and anti-inflammatory potential of the methanolic extract of A. squamosa (EMAS) and palmatine. Methods: The chemical profile of EMAS was evaluated by ultra high-performance liquid chromatography with electrospray ionization coupled to mass spectrometry (UHPLC-ESI/MS). EMAS and palmatine were evaluated in carrageenan-induced pleurisy, zymosan-induced joint inflammation, formalin-induced nociception, and tumor necrosis factor (TNF)-induced mechanical hyperalgesia in experimental models in mice. A cytotoxicity test of EMAS and palmatine was performed using a methylthiazolidiphenyl-tetrazolium (MTT) bromide assay. Results: The analysis of the chemical profile of the extract showed the presence of palmatine, liriodenine, and anonaine. Oral administration of EMAS and palmatine significantly reduced leukocyte migration and oxide nitric production in the carrageenan-induced pleurisy model. EMAS and palmatine reduced mechanical hyperalgesia, leukocyte migration, and edema formation in the joint inflammation induced by zymosan. In the formalin test, palmatine was effective against the second-phase nociceptive response, mechanical hyperalgesia, and cold allodynia. In addition, palmatine reduced mechanical hyperalgesia induced by TNF. EMAS and palmatine did not demonstrate cytotoxicity. Conclusions: The present study showed that A. squamosa and palmatine are analgesic and anti-inflammatory agents, and that the anti-hyperalgesic properties of palmatine may involve the TNF pathway. Palmatine may be one of the compounds responsible for the anti-hyperalgesic and/or anti-arthritic properties of this medicinal plant.

Indigofera truxillensis Kunth is traditionally used in Brazilian folk medicine as an oral infusion of the aerial parts, taken as one cup several times daily for at least one week, to relieve inflammatory pain and gastrointestinal complaints. To chemically characterize and evaluate the anti-arthritic and analgesic properties of the methanolic extract (MEIT) and indigo obtained from the aerial parts of I. truxillensis. The chemical analysis of MEIT and the identification of indigo were performed by electrospray ionization tandem mass spectrometry and nuclear magnetic resonance. Anti-inflammatory and anti-hyperalgesic activities were assessed in mice using carrageenan-induced pleurisy and paw inflammation, complete Freund's adjuvant (CFA), and zymosan-induced articular inflammation models. Cytotoxicity and phagocytic activity were evaluated in vitro using leukocyte viability (MTT) and neutrophil phagocytosis assays. MEIT and indigo significantly inhibited leukocyte recruitment in carrageenan-induced pleurisy. In the carrageenan paw model, both reduced mechanical hyperalgesia, cold sensitivity, and edema. In CFA-induced inflammation, MEIT and indigo decreased mechanical hyperalgesia, cold response, myeloperoxidase activity, and protein exudation. In the zymosan-induced arthritis model, both treatments reduced knee edema, mechanical hyperalgesia, leukocyte migration, protein extravasation, and nitric oxide levels in synovial fluid. MEIT and indigo did not exhibit cytotoxicity in vitro; MEIT reduced neutrophil phagocytosis at specific concentrations, whereas indigo did not alter phagocytic activity. MEIT and indigo exhibit significant anti-inflammatory, anti-hyperalgesic, and anti-arthritic activities, supporting the traditional use of I. truxillensis for painful and inflammatory conditions and identifying indigo as a key bioactive constituent.