Untargeted metabolite analysis of Ocimum leaves shows species specific variations

Abstract

Tulsi (Ocimum species), the queen of herbs is a common ingredient in beverages with perceived health benefits. Recently published Ocimum genome highlighted the presence of several genes that contributes to important phytochemicals but a comprehensive metabolite profiling to study the water soluble metabolites of Ocimum is lacking. In this study, untargeted metabolic profiling of hot water extract of fresh and air dried leaves of O. basilicum, O. sanctum and O. kilimandscharicum species employing gas chromatography and mass spectrometry (GC-MS) was attempted. Analysis of hot water extracts of Ocimum leaves will provide details of molecules consumed and species specific differences, if any. Several metabolic features including amino acids (glycine, serine glutamate), organic and other acids (succinic acid, fumaric acid, 4-amino butanoic acid), sugarsand their derivatives (glucose, sucrose, mannitol, fructose) and secondary metabolites (shikimic acid, quinic acid, catechol, gamma amino butyric acid, eugenol) were identified. Multivariate statistical analysis of GC-MS data indicated several species specific metabolic similarities and differences. Based on variable importance parameter score of >1, it was observed that in case of air dried extracts, glucose, fumaric acid, and D-mannitol displayed as important variables for species specific variation. Whereas in case of fresh leaves extracts, the variation was prominent due to xylose, D-allose and an unknown metabolic feature detected at 24 min (metabolite@24 with highest m/z 75). Phytochemical phenotype of Ocimum leaves not only shows species specific variations but these may partly explain their difference in taste and health benefits from their use as hot beverages. 2