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 C₂₀–C₃₅ (with C₃₁ dominating), iso-alkanes C₂₅–C₃₅, and some aldehydes. The 61% of fraction 2 consisted of 15 triterpenes, namely - and -amyrin, lupeol, glutinol, 3-friedelanol, friedelin, taraxerol, taraxasterol, -amyrin, germanicol, multiflorenol, -taraxasterol, isomultiflorenol, isobauerenol and bauerenol, as well as n-alkanoic acids C₁₆–C₃₂, 2-hydroxy-alkanoic acids C₂₀–C₂₆ and traces of n-alkanols and phytosterols (campesterol, stigmasterol and -sitosterol). For the three eggplant cultivars, 77% of fraction 1 was obtained with (in decreasing order) n-alkanes C₂₃–C₃₆, anteiso-alkanes C₂₉–C₃₆, iso-alkanes C₂₇–C₃₅, and some aldehydes. In the 23% of fraction 2, the n-alkanoic acids C₁₆–C₃₂ predominated compared with the 2-hydroxy-alkanoic acids C₂₂–C₂₆, the n-alkanols C₂₄–C₂₉, triterpenols (- and -amyrin, lupeol, germanicol) and sterols (stigmasterol and -sitosterol).