Proposing a chemometric Normalized Difference Phyllodulcin Index (cNDPI) for phyllodulcin synthesis estimation

The assessment and evaluation of plant traits is a key factor in development of plant based products and exploitation of renewable resources. In this context, phyllodulcin (PD) and its precursor hydrangenol (HG), both dihydroisocoumarins (DHC) only present in Hydrangea macrophylla subsp. serrata (also known as H. serrata (Thunb.) Ser.), are of interest for food industry and medicine. Besides PD content and plant growth, the efficient conversion of PD from HG is an important factor in plant selection. For this a chemometric Normalized Difference Phyllodulcin Index (cNDPI) is proposed as a reliable descriptor for PD biosynthesis efficiency from HG. The cNDPI was tested for robustness and resilience over the course of 1291 measurements in 12 experiments using the H. macrophylla subsp. serrata cultivars ‘Amagi Amacha’, ‘Oamacha’ and ‘Odoriko Amacha’. The cNDPI significantly differentiates these three cultivars with an accuracy of 94.4%. Observations on an F1 population from a cross ‘Odoriko Amacha’ x ‘Yae Amacha’ reveal that cNDPI values are stable over different environments and are not affected by absolute HG or PD contents which are mainly genetically determined. In conclusion, the cNDPI provides a simple tool for quantification of the HG into PD conversion, regardless of absolute DHC amounts or environmental effects. The cNDPI could be used to evaluate efficiency of PD conversion in tea-hortensias.