Chiral NMR analysis reveals the environmental dependence of areolal scalemization in Piptothrix areolare

Abstract

The occurrence of racemic and enantiomerically enriched (scalemic) mixtures of secondary metabolites in their natural sources is a rare phenomenon. The unprecedent case of enantiomeric variations from levorotatory to dextrorotatory, and back to levorotatory, passing through an almost racemic mixture, was recently documented for areolal, the major epoxythymol of Piptothrix areolare. In an attempt to shed some light to understand the reasons for such an unusual behavior, herein, we evaluated this phenomenon by correlating the areolal enantiomeric purity with several environmental variables, including temperature, humidity, rain precipitation, wind speed, and radiation during over 1 year of the plant life cycle. The specific rotation and enantiomeric excess determined by 1H‐NMR‐BINOL measurements provided the scalemic variations of areolal samples isolated from the roots collected from the same location along a 427‐day period. The 1H‐NMR‐BINOL methodology provided better sensitivity to enantiomeric variations than specific rotation measurements. Statistical data, including matrix correlation analysis, exploratory analysis by heatmap plotting, and the principal component analysis (PCA), suggested direct correlation of the scalemic variation with humidity, rain precipitation, and radiation variables with the best PCA explanation (78.4%) and noncritical or poor correlations in PCA explained in 60.2% and 48.4%, respectively. When variations in the optical activity parameter of any metabolite are observed, the search for scalemic mixtures along their host plant life cycle should be undertaken. Herein, this phenomenon could be associated with interactions with soil microorganisms and with evolutionary aspects of Piptothrix areolare which belongs to Asteraceae, one of the most successfully adaptable plant families.

Propagating eelgrass (Zostera marina) from cuttings in land–sea combination systems: a novel method to improve the sustainability of seagrass restoration

“…Prolonged exposure to more suitable environments may lead to long-term adaptations in these plants, potentially resulting in morphological and physiological alterations in their nutrient organs (Velten & Richter 1993). Upon transplantation into natural habitats, abrupt environmental changes threaten plants' normal survival, necessitating excessive energy expenditure for acclimation (G omez-Hurtado et al 2022). Yang et al (2011) and Shi et al (2020) also demonstrated that terrestrial plants subjected to extended laboratory conditions experience environmental stresses upon field transplantation, leading to a decline in plant dry matter content by approximately 30-45% compared with that of laboratory-grown counterparts.…”