Agronomic strategies to enhance bioactive compounds in medicinal and aromatic plants: the role of crop elicitation and drying optimization

Production techniques for medicinal and aromatic plants (MAPs) are constantly evolving, driven by both the need to comply with increasingly stringent health regulations and the requirement to produce a product with a high content of active compounds, as demanded by the market. This study investigated the application of elicitors and the optimization of drying temperature after harvest. Field trials were conducted on Melissa officinalis L., Echinacea purpurea L., and Passiflora incarnata L. over two consecutive years at Agribioenergia S.C.A. The foliar application of chitosan and salicylic acid generally did not affect the total yield both for the fresh and dry weight in each species. Chitosan foliar application is influential in stimulating the production of secondary metabolites such as polyphenols and flavonoids in Melissa officinalis L. and Echincea purpurea L. although with no statistical evidence, the same trend was observed for the antioxidant activity. Application of chitosan resulted in a statistically significant increase in rosmarinic acid content in Melissa officinalis L. despite it did not affect the content in vitexin and cichoric acid in Passiflora incarnata L. and Echinacea purpurea L., respectively. Salicylic acid foliar application generally had no significant effect on the production of secondary metabolites in any of the three species, except for a few non-significant variations. Drying trials revealed that high temperatures caused degradation of phenolic compounds, whereas moderate temperatures (45–50 °C) allowed better preservation of total phenolics. However, in company-scale drying systems, the results were less evident due to the difficulty in achieving uniform drying conditions. Overall, the integration of biostimulant elicitation and optimized drying conditions proved to be aneffective and sustainable approach to enhance the phytochemical quality and functional value of MAPs.