Vinegar-processed frankincense extracts alleviate colorectal cancer by butyric acid mediating M1 tumor-associated macrophage pyroptosis

Background: Olibanum (RF), a traditional Chinese medicinal resin, shows efficacy in colorectal cancer (CRC) treatment. Its vinegar-processed form (PF) is clinically recognized for enhanced therapeutic effects, with prior mechanistic studies focusing on lipophilic components like boswellic acids. Yet, the regulatory mechanisms of PF's aqueous extracts remain unclear. Methods: The aqueous extracts of RF and PF were characterized and compared through transmission electron microscopy (TEM), nanoparticle analysis, and protein profiling. The accumulation of these fractions in feces was confirmed using DiR dye labeling. A mouse CRC model was employed to evaluate and compare the therapeutic effects of RF and PF. The composition of butyric acid-producing microbiota was analyzed using 16S rRNA gene sequencing and metagenomics. Butyric acid levels were quantified using ultra-high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC-TQ-MS). Macrophage phenotypes were assessed via flow cytometry, while mRNA and protein expression levels were determined through RT-qPCR and western blot analysis. Results: PF aqueous extracts exhibited distinct morphology, particle size, and protein content and had a superior therapeutic effect in alleviating CRC compared to RF. Further analysis confirmed that both RF and PF accumulated in feces and modulated the butyric acid metabolism of gut microbiota. The increased levels of butyric acid contributed to CRC alleviation by promoting the polarization of M1 tumor-associated macrophages (TAMs) and suppressing the pyroptosis of M1 TAMs. Conclusion: The study confirmed that vinegar-processed frankincense enhances its therapeutic effect on CRC by modulating M1 tumor-associated macrophages, which may provide efficient treatment of CRC from the perspective of host-gut metabolic interactions.