Revealing the impact of different drying methods on the metabolites and bioactivities of Elsholtzia rugulosa based on untargeted metabolomics combined with chemometrics

Elsholtzia rugulosa Hemsl., a plant with a long history of use as an herbal tea, a honey source, and a folk medicine, is widely distributed in Southwest China. To investigate the effect of various drying approaches on the metabolites and biological activities of E. rugulosa , this study applied an untargeted metabolomics approach, utilizing ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and gas chromatography-mass spectrometry (GC-MS), combined with chemometric analysis of the experimental data. The results indicated that vacuum freeze drying (VFD) yielded the highest contents of total phenols, total flavonoids, and total triterpenoids. In contrast, shade drying (SD) was more effective in preserving total proteins and soluble total sugars; while hot air drying (HAD) resulted in the most abundant volatile metabolites. Dattelic acid and epigallocatechin were identified as the most significantly differential metabolites in E. rugulosa among the three drying methods. Additionally, comparative analysis of metabolic pathways identified flavonoid biosynthesis as the core differentially enriched pathway among various metabolites, underscoring its significance in the metabolic response to drying. Compared with SD and HAD, the VFD resulted in samples with superior inhibitory activities against α -glucosidase, α -amylase, and lipase. For α -glucosidase, α -amylase, and lipase, five differential metabolites were selected as targets for molecular docking studies, all of which exhibited high binding affinities towards their respective receptors. These findings provide a scientific basis for optimizing processing strategies to enhance the health-promoting properties of E. rugulosa . Furthermore, this study offers a systematic insight into the metabolic characteristics and variations in E. rugulosa under three different drying methods, providing a crucial scientific basis for future process-optimization and targeted exploration of bioactive constituents. • The influence of different drying methods on the quality of E. rugulosa was studied. • The contents of total phenols and total flavonoids were the highest in VFD. • VFD exhibited the highest inhibitory effects on α -glucosidase, α -amylase, and lipase. • A total of 73 non-volatile metabolites with significant differences were identified. • The changes in metabolic pathways caused by different drying methods were described.