Mass spectrometry and NMR spectroscopy profiles of red and pink Rhododendron flower petals establish them as rich sources of bioactive secondary metabolites

Rhododendron petals are considered high-value owing to their commercial utility, national/state flower status in certain countries, and bioactive potential from recent studies. Profiling and quantitative analysis of the bioactive metabolites would evaluate if they can be natural sources. This study is focused on comprehensive profiling of secondary metabolites in the petals of Red and Pink Rhododendron flowers (R. arboreum and R. campanulatum) using Mass Spectrometry (GC-MS, LC-MS/MS) and Proton-Nuclear Magnetic Resonance (1H-NMR) Spectroscopy. The profiling highlighted the presence of secondary metabolites belonging to phenolic acids and flavonoids. Specifically, the flowers are rich in promising bioactive molecules such as quinic acid, chlorogenic acid (3-O-caffeoyl quinic acid), protocatechuic acid, coumaroyl quinic acids, catechin, epigallocatechin, and shikimic acid. The profiles are correlated with the metabolic pathways which reflected the activity of shikimic acid, phenolic acid and flavonoid biosynthetic pathways. These metabolites are well reported for their bioactive potential as anti-oxidative, anti-viral, anti-cancerous, anti-diabetic, anti-inflammatory, etc. While the quantitative and multivariate analysis showed variations in the levels of phenolic acids and flavonoids, it is established that red and pink Rhododendron flower petals are a rich source of bioactive phytochemicals of interest to the phytochemical Industry.