The study of the polyphenolic complex and iridoid glycosides in various cultivars of edible honeysuckle fruits Lonicera edulis Turcz. ex Freyn

Abstract

The high content of minor biologically active substances in the fruits of wild-growing and cultivated varieties of honeysuckle, along with the low knowledge of the chemical composition of domestic varieties, determines the relevance of the study of their qualitative and quantitative composition. The aim of the work was to study the detailed composition of the main groups of biologically active polyphenolic compounds [anthocyanins, flavonoids, hydroxycinnamic acids (HCAs), proanthocyanidins] and iridoids in various cultivars of domestic edible honeysuckle fruits (Lonicera edulis Turcz. Ex Freyn). Material and methods. 15 samples of frozen fruits of edible honeysuckle harvested in Tambov, Voronezh, Moscow regions and Karelia were investigated. The total content of polyphenolic compounds (in terms of gallic acid equivalents) was determined by the modified Folin-Ciocalteu method, the total content of monomeric anthocyanins (in terms of cyanidin-3-glucoside) - by pH-differential spectrophotometry, proanthocyanidins (in terms of procyanidin B2) - by the modified Bate-Smith method. The profiles of individual anthocyanins, iridoids, flavonoids and HCAs was determined by HPLC-DAD/TOF-MS. The carbohydrate profile by capillary electrophoresis and antiradical activity in DPPH test in vitro were investigated as well. Results and discussion. The main groups of polyphenolic compounds were anthocyanins and proanthocyanidins. Cyanidin-3-glucoside was found as predominant among anthocyanins (>85% of their sum). Substantial amounts of iridoids (from 78.0 till 341.8 mg/100 g) were found in the honeysuckle examined. The loganic acid and loganine prevailed among iridoids. The total content of flavonoids varied in the range of 9.2- 46.6 mg/100 g, the main of which was rutin. Among HCAs chlorogenic acid prevailed, which accounted for 85.7-90.4% of the total amount of HCAs (45.9-79.8 mg/100 g). A correlation was found between the amount of polyphenolic compounds and the antiradical properties of honeysuckle fruits in DPPH test. Conclusion. Based on the results of the study the most promising varieties of domestic honeysuckle in terms of the highest content of polyphenolic antioxidants and iridoids with potential anti-inflammatory, hypoglycemic, hypolipidemic, antimicrobial and other types of biological activity were determined for the first time.