Chemical Characteristics Associated With Traditional Quality Evaluation in Schizonepeta Spikes: Localization of Constituents in Florets and Rachises

ABSTRACT Aim Schizonepeta spike, the dried spikes of Schizonepeta tenuifolia , are traditionally evaluated based on floret density. However, the chemical basis for this criterion remains unclear. This study aimed to provide scientific insight into this traditional quality evaluation by clarifying the association between floret density (floret‐to‐spike ratio) and pulegone content in whole spikes, and the localization of compounds between florets and rachises. Methods Two accessions of S. tenuifolia were cultivated at six sites in Japan and analyzed by LC‐Q‐TOF‐MS. Correlation analysis was performed between the floret‐to‐spike ratio and pulegone content in whole spikes. Additionally, principal component analysis (PCA) was performed to characterize the localization of compounds between florets and rachises, and the relative abundances of major compounds were compared between them. Results In whole spikes, pulegone content tended to increase with a higher floret‐to‐spike ratio. The PCA based on the comprehensive compounds showed that florets and rachises separated into distinct groups, regardless of cultivation site or accession. Florets showed higher levels of bioactive compounds, including pulegone, luteoloside, and apigetrin, whereas rachises showed higher hesperidin levels than other parts. Conclusion Floret density of Schizonepeta spikes, as described in traditional quality evaluation, was found to be related to pulegone content, which tends to increase as the floret density becomes higher. Moreover, florets were characterized by higher levels of bioactive compounds, including luteoloside and apigetrin, and this localization suggests that the accumulation of these compounds increases in spikes with dense florets. These findings provide chemical insights into the traditional quality evaluation of Schizonepeta spikes.