Uncovering bioactive flavones and volatiles in rice (Oryza sativa L.) leaf tea through dual-platform metabolomics

Seven-day-old jasmine rice seedling leaves contain a significant number of bioactive compounds. In this study, we examined metabolite variations and bioactive compounds in jasmine rice seedling leaves subjected to freeze-drying and sun-drying processes. Using ultra-high-performance liquid chromatography–quadrupole time-of-flight mass spectrometry and headspace gas chromatography/mass spectrometry, we identified luteolin 6- C -glucoside and chrysoeriol 6- C -glucoside as major flavones, and potential bioactive markers. Using hot water at 90 °C for 360 s to brew sun-dried rice leaf tea three times yielded a total of hydrolyzed flavones of approximately 4.70 ± 1.15 mg/g dry weight, which accounted for around 80% of the total flavones. Furthermore, compared to freeze-dried tea leaves, sun-dried leaves exhibited a greater relative abundance of predominant volatile compounds, such as 2-methylbutanal, dodecane, 2-ethylfuran, and methylpyrazine, enhancing consumer appeal in tea infusions. Based on these findings, we propose jasmine rice seedling leaf tea as a health-promoting drink with abundant bioactive compounds. • Lut 6- C -Glu, Chr 6- C -Glu: bioactive markers in rice leaf tea. • 2-Methylbutanal, dodecane, 2-ethylfuran, methylpyrazine: key volatiles in sun-dried leaf tea. • 2-Ethylphenol, 2-methyl-5-(1-methylethyl)phenol, 4-ethyl-2-methylphenol detected in sun-dried samples. • Flavone content peaked when brewing was repeated three times at 90 °C, 360 s. • Sun-drying retains aroma and bioactive phytochemicals.