New Perspectives on Chlorogenic Acid Accumulation in Harvested Leaf Tissue: Impact on Traditional Medicine Preparations

Chlorogenic acids (CGAs) are known as an important class of natural products found in different plant species and are of great interest in diverse research fields. Described as powerful antioxidant agents, these compounds can be found in high concentrations in commonly consumed foods and beverages and in herbal preparations traditionally used in Chinese, Ayurvedic, European, and popular medicines from the new world and are responsible for several pharmacological activities. Considering that diverse mechanisms may possibly be involved in plant metabolite production, herein we evaluated if CGA postharvest accumulation can be a consequence of processes other than anabolism. The objective was to compare the concentrations of chlorogenic acids in leaves subjected to different time-controlled periods of drying at room temperature. A quantitative method, using ultraperformance liquid chromatography tandem mass spectrometry, was developed to monitor the content of CGAs in coffee, lemon, Brazilian cherry, and rosemary leaves. Caffeoylquinic, feruloylquinic, and p-coumaroylquinic acids were accumulated throughout 30 days of postharvest drying in all of the studied species. The results indicate that soft drying is crucial for the accumulation of chlorogenic acids and that their content in plant material may be a consequence of more than just anabolic mechanisms. Knowing that other processes such as catabolism and turnover reactions may participate in the accumulation of natural products, it is possible to discuss the mechanisms that lead to higher concentrations of pharmacologically important substances in different plant species, including plants traditionally used in folk medicine.