Modulation of M1/M2 Cytokines and Inflammatory Enzymes by Persicaria Species Leaf Extracts in Lipopolysaccharide-stimulated RAW 264.7 Cell Macrophages.

Background: Investigating the impacts of plant-based substances on the regulation of pro-inflammatory M1 and anti-inflammatory M2 cytokines could have significant implications for immune-related health conditions. Seven Persicaria plant species from sub-Saharan Africa were specifically selected for analysis, based on their traditional use in treating inflammation.

Objective: To investigate the inhibitory effects of methanol leaf extracts from selected plants on enzymes involved in chronic inflammation.

Methods: The inhibition of nitric oxide production, acetylcholinesterase activity, and 15-lipoxygenase activity was assessed using the Griess reagent method, Ellman's colorimetric method, and the ferrous oxidation-xylenol orange assay. The quantity of M1/M2 cytokines released was quantified using a flow cytometer.

Results: At a concentration of 50 µg/mL, the methanol extracts of P. limbata exhibited the highest NO inhibition (97.67%), followed by P. nepalensis (93.06%) and P. setosula (92.78%). The NO inhibition caused by the plant extracts was correlated directly with the decrease in NO release by the LPS-stimulated macrophages. Furthermore, the pro-inflammatory enzyme assays indicated that the methanol extracts of P. setosula exhibited the highest enzyme inhibitory activity (LOX 89.59%, AChE 72.12 %). This was followed by P. limbata (with 92.76% for LOX and 56.93% for AChE) and P. nepalensis (with 88.16% for LOX and 47.17% for AChE). Cytokine assays revealed that the extracts of P. limbata had significant dose-dependent suppressive effects on IFN-γ and TNF-α expression while promoting the secretion of IL-2, IL-4, IL-6, and IL-10.

Conclusion: Extracts of P. limbata contain immunomodulatory compounds that could be further explored as potential remedies to target the molecular drivers of chronic inflammation.