UV-C radiation elicitation affects the accumulation of secondary metabolites in Ilex paraguariensis callus cultures in a genotype-dependent manner

Abstract Yerba mate ( Ilex paraguariensis A. St.-Hil.) is a species of high economic and cultural importance in South America, widely valued for its bioactive compounds. In vitro culture systems offer a promising platform for the controlled production of secondary metabolites; however, their responsiveness to abiotic elicitors remains poorly understood. In this study, the effects of UV-C radiation on phenolic metabolism and antioxidant responses in callus cultures derived from two genotypes of yerba mate were evaluated. Callus culture were exposed to different UV-C durations (5, 12.5, and 20 min) and analyzed after 6, 39, and 72 h. Phenolic compounds were quantified by HPLC. UV-C exposure induced genotype-dependent and time-dependent responses, with CL2 showing a higher baseline and induced levels of chlorogenic acid compared to CL1. However, UV-C treatment did not promote a consistent increase in phenolic compounds or antioxidant activity. Instead, the responses were characterized by transient changes associated with oxidative stress, followed by partial metabolic recovery. In contrast, field-grown leaves exhibited substantially higher metabolite levels, highlighting the limitations of undifferentiated tissues for secondary metabolite production. Overall, UV-C acted primarily as a stressor rather than an effective elicitor of phenolic biosynthesis under the tested conditions. These findings highlighted the importance of optimizing exposure conditions and sampling timing when applying abiotic elicitors to in vitro systems.