Flavor chemistry and bioactivity of Szechuan pepper (Zanthoxylum Genus): Bridging Má aroma, Má sensation, and bitter compounds

Background: Szechuan pepper is known for its unique cross-modal flavor, combining Má aroma (olfaction), Má sensation (chemesthesis), and bitterness (gustation). While previous reviews have addressed its overall sensory properties, a comprehensive review of recent progress in identifying its key flavor components and elucidating the associated physiological mechanisms has yet to be undertaken. Scope and approach: This review compares the Má aroma profiles of red and green Szechuan pepper. It examines the mechanisms underlying the Má sensation, the structure–activity relationships of alkylamides, and their interactions with other flavor constituents. The contribution of non-alkylamide compounds to Má sensation is also considered. It synthesizes current evidence on the neurophysiological activity of key aromatic compounds and alkylamides. Additionally, recent advances in the identification of bitter compounds, their sensory transduction mechanisms, and associated bioactivities are reviewed. Key findings and conclusions: Red Szechuan pepper exhibits spicy and floral-sweet notes from its abundant esters, conferring superior persistence and stability. In contrast, green pepper presents a sharp, herbaceous aroma dominated by terpenes and alcohols, though it is more volatile and less persistent. Structure–activity analysis of alkylamide reveals that hydroxylation enhances Má sensation intensity, longer alkyl chains prolong duration, and double-bond stereochemistry influences tingling versus numbing quality. Alkylamides synergistically enhance saltiness, while coumarins also contribute to Má sensation. Some aromatic substances and alkylamides exhibit a range of neuroprotection activities. Bitter compounds, which include amino acids, flavonoids, and alkaloids, display various bioactivities. Future studies should focus on clarifying the interactive mechanisms among these flavor components.