Effects of Growth Stages on Leaf Nutrients, Metabolites, and Polyphenols of Three Varieties of Haskap

Haskap (<i>Lonicera caerulea</i> L.) has gained much research interest, given the diverse biologically active compounds found in different parts of the plant. It is, therefore, important to study the concentration of some of these biologically active compounds at different developmental stages. The present study investigated the effect of growth stages on nutrients, metabolites, and polyphenol concentrations in the leaves of three haskap varieties (Indigo Gem, Wojtek, and Jolanta). A targeted quantitative metabolomics approach was used to analyze the haskap leaves using a combination of direct injection mass spectrometry with a reverse LC-MS/MS custom assay. The results showed that the concentrations of soluble sugar, organic acids, polyphenols, and amino acids in the leaves of different varieties of haskap were decreased at the fruiting stage. The leafing stage may be the best period to harvest haskap leaves with the highest nutrients and polyphenol concentrations. Studies on polyphenols and nutrient characterization of haskap leaf at the leafing stage could be further investigated.