Detection and quantification of flavoalkaloids in different tea cultivars and during tea processing using UPLC-TOF-MS/MS

•Fifty-one tea cultivars were screened for high levels of flavoalkaloids.•Cultivars Yiwu and Bulangshan contained the highest level of flavoalkaloids.•Heating during tea processing affects content of flavoalkaloids.•Boiling EGCG and theanine yielded six flavoalkaloid isomers.•Flavoalkaloids could be used to monitor tea processing and quality.