Profiling the dynamic alterations of metabolites and phytohormones in response to stress during the post-harvest processing of Pogostemon cablin leaves

The post-harvest processing of Pogostemon cablin has a direct impact on its medicinal value and economic benefits. The formation of secondary metabolites during this processing stage is potentially a result of the leaves' defensive mechanisms in response to various stresses. Within this intricate process, plant hormones play a pivotal regulatory role. Given the above, an examination was conducted into the dynamic fluctuations of phytohormones and metabolites throughout the drying procedures that encompassed both sweating and oven treatments. The findings revealed a consistent pattern where the concentrations of ABA, SA, and JA progressively intensified as the post-harvest processing progressed. Through comprehensive targeted metabolomics, a grand total of 1735 metabolites were recognized. Of these, 389 differential metabolites were selected for further investigation. Notably, the antioxidant mechanisms demonstrated notable disparities between the two processing methodologies. Specifically, sweating treatment was found to foster the accumulation of nicotinic acid, whereas oven treatment led to a more pronounced accumulation of ascorbic acid. Furthermore, the end product derived from sweating treatment exhibited a marginally higher content of essential oils. A total of eleven metabolites were pinpointed as distinct markers that differentiated between the two processing approaches. Correlation analysis illuminated that early post-harvest differential metabolites displayed significant correlations with ABA and JA, while the late-stage metabolites not only maintained these correlations but also established additional associations with SA. These discoveries provide profound insights into the intricate interplay that exists between metabolic composition and plant hormone regulation during the post-harvest processing of Pogostemon cablin.