APPLICATION OF MICROCOLUMN HPLC-UV FOR RAPID QUANTITATIVE ANALYSIS OF ARBUTIN, BERGEN-IN AND GALLIC ACID IN BERGENIA CRASSIFOLIA

This work is aimed at the development of a microcolumn HPLC-UV assay for the rapid quantitative analysis of arbutin, bergenin, and gallic acid in Bergenia crassifolia. The results obtained indicate appropriate metrological parameters of the developed assay. It was found that the known methods of quantitative analysis of phenolic glycosides using SPE-spectrophotometry cannot be characterized as selective and accurate, due to the fact that the presences of the impurity compounds that do not belong to the group of phenolic glycosides negatively influenced the results. The developed assay was used for quantitative analysis of wild and commercial samples of B. crassifolia raw material. It was found that the content of arbutin, bergenin, and gallic acid in samples of B. crassifolia rhizomes collected in the Republic of Buryatia was 38.58–45.97, 66.74–139.76 and 1.22–1.65 mg/g, respectively, and for commercial batches of raw materials 20.57–41.37, 35.04–83.94 and 0.22–1.28 mg/g, respectively. It was found that the process of gradual enzymatic changes in the color of B. crassifolia leaves (green, red, black) leads to significant changes in the chemical composition. The most pronounced phenomenon is the degradation of bergenin, the presence of which is noted only in green leaves. The concentration of gallic acid is reduced in black leaves. Arbutin is characterized by an increased content in red leaves (102.02 mg/g). Additionally, a quantitative analysis of the peduncles and flowers of B. crassifolia was realized, and it was shown that they are distinguished by a high content of arbutin 48.40 and 42.15 mg/g, respectively, as well as bergenin in flowers (16.89 mg/g). The study demonstrated that the developed technique can be applied for a quick, selective, and accurate quantitative analysis of three compounds in various organs of B. crassifolia.

New Phenolic Glycosides and Lignans from the Roots of Lilium dauricum

Three new phenolic glycosides, carvacrol-2-O-β-D-apiofuranosyl-(1 → 6)-β-D-glucopyranoside (1), 1-methyl-3-isopropylphenol-4-O-β-D-apiofuranosyl-(1 → 6)-β-D-glucopyranoside (2), p-methoxythymol-5-O-β-D-apiofuranosyl-(1 → 6)-β-D-glucopyranoside (3), and a pair of new 8-O-4′ neolignan enantiomers (5a/5b), together with 26 known compounds (4, 6 – 30) were isolated from the roots of Lilium dauricum. The structures of the new compounds were elucidated based on extensive spectroscopic and chemical methods, and the absolute configurations of 5a and 5b were established by electronic circular dichroism analysis. Nine compounds (1, 3, 4, 8, 9, 17, 25, 29, and 30) exhibited potent α-glucosidase inhibitory activity with IC50 values ranging from 73.4 µM to 988.2 µM. Besides, compound 19 displayed strong anticomplementary activity (CH50: 71.6 µM).

Compositional Changes in Grapes and Leaves as a Consequence of Smoke Exposure of Vineyards from Multiple Bushfires across a Ripening Season

The negative effects of smoke exposure of grapes in vineyards that are close to harvest are well documented. Volatile phenols in smoke from forest and grass fires can contaminate berries and, upon uptake, are readily converted into a range of glycosylated grape metabolites. These phenolic glycosides and corresponding volatile phenols are extracted into the must and carried through the winemaking process, leading to wines with overtly smoky aromas and flavours. As a result, smoke exposure of grapes can cause significant quality defects in wine, and may render grapes and wine unfit for sale, with substantial negative economic impacts. Until now, however, very little has been known about the impact on grape composition of smoke exposure very early in the season, when grapes are small, hard and green, as occurred with many fires in the 2019–20 Australian grapegrowing season. This research summarises the compositional consequences of cumulative bushfire smoke exposure of grapes and leaves, it establishes detailed profiles of volatile phenols and phenolic glycosides in samples from six commercial Chardonnay and Shiraz blocks throughout berry ripening and examines the observed effects in the context of vineyard location and timing of smoke exposure. In addition, we demonstrate the potential of some phenolic glycosides in leaves to serve as additional biomarkers for smoke exposure of vineyards.