Effect of cultivation conditions, maturity stage, and harvest time on ergothioneine content of Gastrodia elata rhizome

This study aimed to develop a robust analytical method for quantifying ergothioneine (ERG) in the rhizome of Gastrodia elata using high-performance liquid chromatography with a photodiode array detector (HPLC-PDA) and to evaluate the effects of the extraction method, cultivation type, maturity stage, and harvest time on ERG content. The method exhibited excellent linearity over the range of 1.953-250 μg/mL, with limits of detection (LOD) and quantitation (LOQ) of 4.12 and 12.48 μg/mL, respectively. ERG levels were consistently higher in rhizomes cultivated in indoor facilities compared with outdoor fields, regardless of maturity stage. Among plant parts, the flower bud contained significantly greater ERG concentrations than the cortex or epidermis, indicating a distinct distribution pattern. Seasonal variation was also evident; autumn (October)-harvested samples (0.40±0.03 mg/g DW) contained approximately 1.6-fold higher ERG than those harvested in spring (April) (0.25±0.04 mg/g DW). These findings demonstrate that cultivation under controlled indoor conditions and harvesting in autumn can substantially enhance ERG level in G. elata rhizome. The established HPLC-PDA method provides a sensitive and reliable approach for ERG quantification and can serve as a valuable tool for quality control, functional food development, and the optimization of cultivation practices aimed at maximize ERG content.