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The current study was aimed at evaluating the antihyperalgesic effects of lignans (phyllanthin and hypophyllanthin) and tannin (corilagin) rich three standardized extracts of Phyllanthus amarus in a model of chronic musculoskeletal inflammatory pain. Three percent carrageenan injected in the gastrocnemius muscle produced hyperalgesia to mechanical and heat stimuli ipsilaterally, which spreads to the contralateral side within 7 to 9 days. To investigate the effects on chronic thermal and mechanical hypersensitivity, three extracts of P. amarus in three doses (100, 200, and 400 mg/kg) were administered to animals intraperitoneally from 14th day to 22nd day after intramuscular injection of carrageenan. It was observed that intraperitoneal administrations of Phyllanthus extracts showed antihyperalgesic activity, as they elevated thermal and mechanical threshold, which was supported by histopathological observations along with reduction in prostaglandin E2 (PGE2) concentration. In conclusion, we strongly suggest that the observed antihyperalgesic and antiinflammatory effects of P. amarus in current pain model are mediated via spinal or supraspinal neuronal mechanisms, mainly by inhibition of PGE2. Modulation of chronic muscular inflammation may be due to presence of phytoconstituents like phyllanthin, hypophyllanthin, and corilagin, which offers a promising means for treatment of chronic muscle pain., (Copyright © 2015 John Wiley & Sons, Ltd.)

Fibromyalgia (FM) is characterized by chronic pain and heightened sensitivity to painful stimuli. This study investigated the potential of Niranthin (NR), a natural compound derived from Phyllanthus species, in a rat model of FM. We employed a multifaceted approach to comprehensively assess the potential benefits of NR as a treatment for FM, including in-vivo analysis, molecular docking studies, and molecular dynamics (MD) simulations, and Density Functional Theory (DFT) calculations. Three doses of NR (5 mg/kg, 10 mg/kg and 20 mg/kg) significantly reduced mechanical allodynia induced by acidic saline injections. In an acute study, NR dosing increased the mechanical threshold in both ipsilateral and contralateral paws. In a four-day study, twice-daily NR treatment further elevated the mechanical threshold. Temporary treatment interruption led to a re-establishment of allodynia, but subsequent reinitiation of NR treatment remained effective, ruling out tolerance development. MD simulations were conducted to investigate the stability and dynamics of NR-target complexes, revealing stable binding interactions and conformational changes associated with NR binding. Docking calculations indicated that the NR molecule had a similar binding affinity to the drug Amiloride towards Acid-sensing ion channels (ASICs). NR showed interactions with amino acid residues, including LYS 373, ARG 370, GLU 374 and GLN 277. DFT calculations provided insights into the electronic and structural properties of NR and its interactions with FM-related molecular target ASICs. We propose that NR may modulate ASICs, leading to decreased pain sensitivity in FM rats. However, further research is required to fully understand the mechanism of action and explore NRs therapeutic potential for the treatment of FM. Fibromyalgia, a condition characterized by chronic pain and heightened pain sensitivity, was studied with Niranthin (NR), a natural compound from Phyllanthus species. Various NR doses reduced mechanical allodynia in a rat model of fibromyalgia, and NR doses improved mechanical thresholds. NR exhibited strong binding affinity to ASICs, similar to the drug Amiloride. NR interacted with specific amino acid residues, suggesting its potential role in modulating ASICs. Therapeutic Potential: NR shows promise in decreasing pain sensitivity in fibromyalgia rats, but further research is required to understand the mechanism fully and assess its therapeutic potential. [ABSTRACT FROM AUTHOR]