Diurnal Metabolomic Profiling of Cardiac Glycosides Metabolites in Calotropis procera Following Water Treatment Under Arid Conditions in Jeddah, Saudi Arabia

Calotropis procera is a drought‐tolerant desert shrub that produces cardenolides and triterpenoids of ecological and pharmacological interest; however, their short‐term temporal profiles under arid field conditions remain incompletely characterized. We used targeted UPLC–MS/MS to examine relative diurnal profiles of selected metabolites in field‐grown C. procera near Jeddah, Saudi Arabia, before and following a single watering event. Leaves from individually marked plants were collected at dawn, midday, and predusk on the day before watering and at matched time points on the following day. Relative peak‐area profiles were obtained for calotropagenin, uzarigenin diglycoside, uzarigenin aglycone, β‐sitosterol, and α‐amyrin. In parallel, RNA‐seq quality assessment and phylogenetic analyses were performed to support annotation of sequences encoding flavonol oxygenase, amyrin synthase, calreticulin, and oxysterol‐binding protein. The relative profiles of the targeted cardenolides and terpenoids differed among diurnal sampling times and between the prewatering and postwatering sampling periods. Calotropagenin and uzarigenin diglycoside showed higher relative proportions at midday during the prewatering sampling period, whereas α‐amyrin remained the predominant terpenoid across sampling periods. Samples collected following watering showed altered relative proportions of calotropagenin, uzarigenin derivatives, and β‐sitosterol compared with the prewatering baseline. Phylogenetic analyses supported the annotation of the selected C. procera gene sequences as putative plant orthologues. These insights help explain the ecological success of C. procera in deserts and provide a framework for optimizing irrigation and harvest regimes to enhance the yields of cardenolides and triterpenoids of high‐value.