Application of on-line and off-line heart-cutting LC in determination of secondary metabolites from the flowers of Lonicera caerulea cultivar varieties.

Lonicera caerulea is a shrub native to the Northen Hemisphere, with its fruits having a long tradition of being used in traditional medicine. The flowers, although a potential source of diverse phenolic compounds have not been studied in terms of phenolic content. In this paper, a 2D LC heart-cutting system, operating in both on-line and off-line modes, was developed and successfully employed in identification and quantification of secondary metabolites in the flowers of L. caerulea. A total of 51 compounds have been resolved and identified as either flavonoids, phenolic acids or iridoids. Flavonoids were the dominating group of compounds, alongside substantial levels of both phenolic acids and iridoids. A comparison between three varieties of L. caerulea flowers revealed that 'Wojtek' contained markedly more flavonols and phenolic acids than the remaining two varieties, whereas iridoids were at similar levels. Heart-cutting 2D LC method used in this study offers a convenient approach and an effective tool for secondary metabolite analysis in L. caerulea flowers, and possibly other species from the genus.