Abstract:

Purpose: To establish a simple, rapid, accurate high performance liquid chromatography-tandem mass
spectrometry (HPLC-MS/MS) for the simultaneous separation and determination of phenolic compounds in leaves, stems
and roots of Perilla frutescens and further to examine the accumulation patterns of phenolics in different plant parts during
the growing period for the purpose of determining the optimal harvest time for Perilla frutescens. Methods: Samples
of cultivated Perilla frutescens were collected at three different growing stages and extracted with ethanol for HPLCMS
analysis. The important chromatographic and mass spectrometric parameters were optimized. The identification of
phenolic compounds was done by retention time comparison with reference standards and quantitation was performed using
calibration curves. Moreover, changes in the contents of 13 major phenolic compounds in various parts of Perilla frutescens
at different growing stages were observed. Results: The following compounds were identified: caffeic acid, caffeic acid-3-
O-glucoside, rosmarinic-acid, rosmarinic-acid-3-O-glucoside, luteolin, luteloin-7-O-glucoside, luteloin-7-O-diglucuronide,
luteloin-7-O-glucuronide, apigenin, apigenin-7-O-caffeoyglucoside, apigenin-7-O-diglucuronide and scutellarein-7-Odiglucuronide.
Among these, the contents of rosmarinic acid and its glucoside derivatives decreased initially and then sharply
increased to the maximum at the fruiting stage, while the flavonoids and their glucoside derivatives gradually increased
until reaching the maximum at the fruiting stage. The contents of rosmarinic acid and luteloin-7-O-glucuronide in leaves at
the fruiting stage were the highest, reaching 21.41 mg/g and 19.89 mg/g, respectively. Furthermore, leaves at the fruiting
stage had the highest total phenol content of 47.50 mg/g among the various parts examined. Conclusions: The results of our
present work may provide a good reference for the utilization of Perilla frutescens as a phenolics resource.

Key words: Perilla frutescens, phenolics, high performance liquid chormatography-tandem mass spectrometry (HPLC-MS/MS), accumulation, optimal harvest time