Changes in the Triterpenoid Content of Cuticular Waxes during Fruit Ripening of Eight Grape (Vitis vinifera) Cultivars Grown in the Upper Rhine Valley

Abstract

Triterpenoids present in grape cuticular waxes are of interest due to their potential role in protection against biotic stresses, their impact on the mechanical toughness of the fruit surface, and the potential industrial application of these biologically active compounds from grape pomace. The determination of the triterpenoid profile of cuticular waxes reported here supplements existing knowledge of the chemical diversity of grape, with some compounds reported in this species for the first time. Common compounds identified in eight examined cultivars grown in the Upper Rhine Valley include oleanolic acid, oleanolic and ursolic acid methyl esters, oleanolic aldehyde, α-amyrin, α-amyrenone, β-amyrin, cycloartanol, 24-methylenecycloartanol, erythrodiol, germanicol, lupeol accompanied by lupeol acetate, campesterol, cholesterol, sitosterol, stigmasterol, and stigmasta-3,5-dien-7-one, whereas 3,12-oleandione was specific for the Muscat d'Alsace cultivar. Changes in the triterpenoid content of cuticular waxes were determined at three different phenological stages: young grapes, grapes at véraison (the onset of ripening), and mature grapes. The results reveal a characteristic evolution of triterpenoid content during fruit development, with a high level of total triterpenoids in young grapes that gradually decreases with a slight increase in the level of neutral triterpenoids. This phenomenon may partially explain changes in the mechanical properties of the cuticle and possible modulations in the susceptibility to pathogens of mature grapes.

Triterpenoid profile of fruit and leaf cuticular waxes of edible honeysuckle Lonicera caerulea var. kamtschatica

“…The fruit cuticular wax of edible honeysuckle contains a strikingly low amount of triterpenoids (only 6.25% of the total wax extract), which is a feature that clearly distinguishes this berry (a member of the Caprifoliaceae) from edible berries of plants belonging to other families, e.g., bilberry Vaccinium myrtillus L. [20], cowberry V. vitis-idaea L. [19,28], and cranberry V. macrocarpon Ait. of the Ericaceae [29] or grapevine Vitis vinifera L. of Vitaceae [21,22].…”

“…Extracts were fractionated by adsoption chromatography as described previously [19][20][21][22] on silica gel plates in the solvent system CHCl 3 /MeOH (97:3, v/v). Fractions were localized on plates by comparison with standards (oleanolic acid, α-amyrin, and sitosterol) and eluted from the gel in diethyl ether.…”

“…Three fractions, i.e., triterpene acids, combined fraction of free (non-esterified) triterpene alcohols and sterols (referred to as neutral triterpenoids), and triterpenoid esters (extracted from the line of the solvent) were obtained. The fractions containing free triterpene alcohols and sterols were directly analyzed by GC-MS without derivatization, whereas prior to this analysis, fractions containing triterpene acids were methylated with the solution of diazomethane in diethyl ether at 2°C for 24 h, and those containing triterpene esters were subjected to alkaline hydrolysis with 10% NaOH in 80% MeOH at 80°C for 3 h [19][20][21].…”

“…and NIST 2008 Lib. SW (databases version 2010), and where available, by comparison of their retention times and corresponding mass spectra with those of authentic standards [19][20][21][22]. Quantification was based on measuring the area of peaks in the GC-FID chromatograms and performed with the use of external standard method, i.e., calibration curves prepared separately for known concentrations of standards belonging to main triterpenoid classes (α-amyrin for triterpene alcohols, oleanolic acid methyl ester for acids, sitosterol for sterols).…”

“…Identified compound Mass spectrum m/z (relative intensity) (27), 41 (21) all triterpenoids, 66% of tetracyclic compounds). A considerable amount of cholesterol, which has been reported as a minor constituent of surface waxes of some other plants [23,24], was detected in both the fruit and leaf waxes of honeysuckle.…”