Corn (ZEA MAYS L). extracts as source of active compounds with promising effects in reducing trigeminal pain through microbiota modulation

Objective Corn (Zea mays) is a valuable source of polyphenols with potential healthy properties. The purpose of the study was: 1) a chemical characterization of different corn varieties, including yellow, pigmented and hybrid corns; 2) to assess the role of anthocyanins from pigmented corns in modulating trigeminal pain and the gut microbiota balance. Methods Spectrophotometric methods were used to characterize the total polyphenol and anthocyanin content in corn extracts and to measure their antioxidant activity. Trigeminal pain was stimulated by unilateral injection of Complete Freund’s Adjuvant in male rats that had received for 10 days extracts from: 1) yellow corn, 2) anthocyanin-rich purple corn, or 3) water as controls. Microglia/macrophages activation was analyzed by immunohistochemistry. The bacterial taxonomic profile was studied from fecal samples by 16S rRNA profiling protocol. Results Corn varieties showed an interesting polyphenol profile, with a total content ranging between 3.61 and 11.12 mg/g dry weight (gallic acid equivalents); this content was well correlated with the antioxidant activity (R2>0.90). If compared with yellow varieties, purple corn administration prevented orofacial allodynia and the trigeminal infiltration of macrophages. In addition, purple corn modulated the gut microbiota composition toward an anti-inflammatory taxonomic profile. Conclusions Selected corn varieties could represent a dietetic source of polyphenols with anti-inflammatory and antioxidant activity able to prevent trigeminal pain through different mechanisms. Further studies are in progress to investigate the correlation between the polyphenol profile and the biological activity of different corn varieties, with particular attention to the possible involvement of the gut-brain axis.