Composition of the surface waxes from bell pepper and eggplant

Surface waxes from the skins of bell pepper (Capsicum annuum) and eggplant (Solanum melongena) were rinsed with tert-butylmethyl ether (TBME). The wax components were separated into two fractions by elution from a small silica gel column with toluene/hexane (2+1) followed by methanol. They were identified by GC/MS and quantitatively determined by GC/FID. For 12 bell pepper cultivars, fraction 1 made up 39% of the total and contained mainly n-alkanes C-20-C-35 (with C-31 dominating), iso-alkanes C-25-C-35, and some aldehydes. The 61% of fraction 2 consisted of 15 triterpenes, namely alpha- and beta-amyrin, lupeol, glutinol, 3beta-friedelanol, friedelin, taraxerol, taraxasterol, delta-amyrin, germanicol, multiflorenol, omega-taraxasterol, isomultiflorenol, isobauerenol and bauerenol, as well as n-alkanoic acids C-16-C-32, 2-hydroxy-alkanoic acids C-20-C-26 and traces of n-alkanols and phytosterols (campesterol, stigmasterol and P-sitosterol). For the three eggplant cultivars, 77% of fraction I was obtained with (in decreasing order) n-alkanes C-23-C-36, anteiso-alkanes C-29-C-36, iso-alkanes C-27-C-35, and some aldehydes. In the 23% of fraction 2, the n-alkanoic acids C16-C32 predominated compared with the 2-hydroxy-alkanoic acids C-22-C-26, the n-alkanols C-24-C-29, triterpenols (alpha- and beta-amyrin, lupeol, germanicol) and sterols (stigmasterol and beta-sitosterol).