Therapeutic effects of self-assembled berberine-glycyrrhizic acid and matrine-glycyrrhizic acid complexes from Qingchang Wenzhong decoction on DSS-induced ulcerative colitis: Mechanisms of anti-inflammatory action.

ETHNOPHARMACOLOGICAL RELEVANCE: Qingchang Wenzhong Decoction (QCWZD), a traditional Chinese medicine (TCM) formula, has been clinically utilized for ulcerative colitis (UC) treatment due to its anti-inflammatory and intestinal barrier-protective effects. However, the mechanisms by which its naturally self-assembled supramolecular complexes, formed during aqueous decoction, contribute to therapeutic outcomes remain underexplored, representing a critical gap in understanding TCM's holistic pharmacology.

AIM OF THE STUDY: This study sought to elucidate the self-assembly mechanisms underlying QCWZD's therapeutic effects, with a focus on characterizing the anti-inflammatory properties of its naturally self-assembled complexes formed during decoction and their role in UC intervention.

METHODS

The submicron precipitate of QCWZD was isolated via gradient centrifugation and characterized for size and morphology using dynamic light scattering (DLS) and scanning electron microscopy (SEM). A DSS-induced murine UC model was used to evaluate the efficacy of QCWZD and its fractions (supernatant and submicron precipitate). Meanwhile, UPLC-ZenoTOF-MS/MS and triple quadrupole LC-MS/MS were employed to identify and quantify the bioactive components. Representative self-assembled complexes were synthesized under conditions mimicking decoction and characterized using DLS and SEM. Thermodynamic binding behavior was probed using isothermal titration calorimetry (ITC). Non-covalent interaction mechanisms of complex formation were characterized by UV, FT-IR, and 1H NMR spectroscopy. Anti-inflammatory activity of the self-assembled complexes was validated in LPS-stimulated RAW264.7 macrophages.

RESULTS

QCWZD's submicron precipitate accelerated UC remission in mice, reducing the disease activity index (DAI), restoring colon length, and suppressing NF-κB p65 phosphorylation compared to the model group. Mass spectrometry identified berberine-glycyrrhizic acid (BER-GL) and matrine-glycyrrhizic acid (MAT-GL) as dominant self-assembled complexes. ITC revealed binding affinity between glycyrrhizic acid (GL) and alkaloids (BER: Kd = 2.55 × 10-4 M, 1:1 binding ratio; MAT: Kd = 6.77 × 10-4 M, 1:2 binding ratio), driven by enthalpy. Charge-transfer and hydrogen-bonding interactions between glycyrrhizic acid (GL) and the alkaloids berberine (BER) and matrine (MAT) lead to stable self-assemblies. BER-GL and MAT-GL complexes significantly suppressed pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) while upregulating IL-10 in RAW264.7 cells, outperforming free alkaloids.

CONCLUSION

Building on QCWZD's established efficacy in treating ulcerative colitis (UC) via the NF-κB pathway, this work demonstrates that the aqueous self-assembly of BER-GL and MAT-GL, derived from QCWZD's submicron precipitate fraction, critically enhances anti-inflammatory efficacy. These findings bridge TCM's traditional preparation methods with supramolecular pharmacology, providing a mechanistic framework for the holistic effects of herbal decoctions. The study advances ethnopharmacological research by highlighting natural self-assembly as a key determinant of TCM's therapeutic synergy.