A novel approach to incorporate compound dissimilarity to plant chemodiversity measures using UV-Vis spectra

Plants interact with their environment through intricate combinations of phytochemicals, rather than metabolites alone. Quantifying plant chemodiversity, which considers the variety of chemical compounds within a plant species, is becoming increasingly important. However, structural disparity, or differences in chemical structure, has largely been overlooked in measures of chemodiversity due to the need for known compound identity. This limitation hinders the broad application of these measures.

To address this issue, researchers have developed an innovative approach that derives compound dissimilarity from UV-Vis (ultraviolet-visible) spectra in HPLC-DAD (high-performance liquid chromatography-differential absorption) datasets. This method was evaluated in relation to other approaches based on structure or biosynthesis, and its potential contributions to chemodiversity measures were examined.

The approach was tested in an experiment that explored the effects of drought and herbivory on the chemodiversity of Solanum dulcamara, a type of nightshade plant.

The results showed that UV-Vis spectral dissimilarity aligned well with structural dissimilarity based on molecular connectivity and revealed structural relationships within a set of standards. By incorporating this new measure into chemodiversity analysis, the separation of the effects of drought and herbivory was improved. This was particularly evident when both stresses were combined, as their distinct impacts on different leaf metabolites were only fully reflected when accounting for compound disparity.

This study demonstrates that UV-Vis spectral dissimilarity can capture chemically meaningful compound relationships without the need for compound identity. By using it as a proxy for compound disparity, researchers can add a biologically relevant dimension to measures of chemodiversity. This approach not only enhances the understanding of plant chemodiversity but also has broader implications for assessing the functional consequences of phytochemical diversity in response to environmental factors such as drought and herbivory.