Identification of Iridoids in Edible Honeysuckle Berries (Lonicera caerulea L. var. kamtschatica Sevast.) by UPLC-ESI-qTOF-MS/MS

Alicja Kucharska,Izabela Fecka

doi:10.3390/molecules21091157

Abstract

Iridoid profiles of honeysuckle berry were studied. Compounds were identified by ultra-performance liquid chromatography coupled with electrospray ionization mass spectrometry UPLC-ESI-qTOF-MS/MS in positive and negative ions mode. The MS fragmentation pathways of detected iridoid glycosides were also studied in both modes. In the negative ESI mass spectra, iridoids with a methyl ester or lactone structure have preferentially produced adduct [M + HCOOH − H]− ions. However, protonated ions of molecular fragments, which were released by glycosidic bond cleavage and following fragmentation of aglycone rings, were more usable for iridoid structure analysis. In addition, the neutral losses of H2O, CO, CO2, CH3OH, acetylene, ethenone and cyclopropynone have provided data confirming the presence of functional substituents in the aglycone. Among the 13 iridoids, 11 were identified in honeysuckle berries for the first time: pentosides of loganic acid (two isomers), pentosides of loganin (three isomers), pentosyl sweroside, and additionally 7-epi-loganic acid, 7-epi-loganin, sweroside, secologanin, and secoxyloganin. The five pentoside derivatives of loganic acid and loganin have not been previously detected in the analyzed species. Honeysuckle berries are a source of iridoids with different structures, compounds that are rarely present in fruits.

Highlights

Lonicera caerulea L. var. kamtschatica Sevast. (Caprifoliaceae) is a fruit bush originating from the Far East of Russia (Kamchatka Peninsula)
Chromatogram of honeysuckle berry extract, obtained in the UV spectral region (254 nm), is shown in Iridoids with methyl ester or lactone structure showed a strong tendency for associated product ion formation in negative ionizations; MS data of ions of these and other compounds, in both negative and positive ionization modes, were investigated (Table 1)
The study shows that in honeysuckle berries there is a range of different iridoids, which are rarely present in edible fruits

Summary

Introduction

Lonicera caerulea L. var. kamtschatica Sevast. (Caprifoliaceae) is a fruit bush originating from the Far East of Russia (Kamchatka Peninsula). Edible honeysuckle berries are gaining popularity in many European countries, Japan, China, Canada and others. These berries are good fresh fruit for consumption and good raw material for the production of juices, snacks, dry fruits, and jams [1,2,3]. Iridoids are a large group of secondary metabolites found both in a variety of plant and selected animal species They belong to the monoterpenes with a cyclopentanopyran skeleton and occur in plant materials naturally as glucoside forms. Iridoids, depending on the chemical structure, exhibit different pharmacological properties, such as antibiotic, anti-inflammatory or hypertensive activities [9].

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