Plant Growth Modulates Metabolites and Biological Activities in Retama raetam (Forssk.) Webb

Abstract

This work focuses on the variability of Retama raetam (Forssk.) Webb bioactive compounds as a function of the plant cycle. The main results showed that it exhibited the highest percentage of polyunsaturated fatty acids, along with superior levels of vitamin C and total phenolic compounds (66.49%, 645.6 mg·100 g−1 FW and 23.9 mg GAE·g−1, respectively) at the vegetative stage. Instead, at the flowering and mature fruiting stages, R. raetam (Forssk.) Webb exhibited notable contents of proline (25.4 μmol·g−1 DW) and carotenoids (27.2 μg·g−1 FW), respectively. The gathered data concerning the antioxidant activity highlighted the effectiveness of the vegetative stage in comparison to the other periods. Actually, IC50 and EC50 values of the hydromethanolic extract obtained from the plant shoots at the vegetative stage were of 23, 380, 410, 1160 and 960 μg·mL−1 (DPPH• and ABTS•+ radicals scavenging activity, reducing power, chelating power and β-carotene bleaching activity, respectively). Furthermore, the four studied stages showed appreciable antibacterial capacities against human pathogens with a higher efficiency of the vegetative stage extract. Finally, the LC-DAD-ESI/MSn analysis revealed the predominance of isoflavonoids as main class of phenolic compounds and demonstrates that individual phenolic biosynthesis was clearly different as a function of plant growth. These findings highlight that reaching the optimum efficiency of R. raetam (Forssk.) Webb is closely linked to the physiological stage.