Comparative analysis of three Australian finger lime (Citrus australasica) cultivars: Identification of unique citrus chemotypes and new volatile molecules Estelle Delort ⇑ , Alain Jaquier, Erik Decorzant, Christian Chapuis, Alessandro Casilli 1 , Eric Frérot Firmenich SA, Corporate R&D Division, Geneva, Switzerland article info Article history: Received 4 June 2014 Received in revised form 15 October 2014 Available online 11 November 2014 Keywords: Alstonville Judy’s Everbearing Durham’s Emerald 6-Methyl-1-octylacetate Isoascaridole Citronellyl citronellate 1,2:5,6-Diepoxy-p-menthane 2,3-Epoxy-p-menthan-6-one p-Menth-1-en-3-ol-6-one 1,2-Epoxy-p-methan-5-one 4-Hydroxy-6-isopropyl-3-methylcyclohex- 2-enone abstract The volatile constituents of the peel of three cultivars of Australian finger lime (Citrus australasica) were investigated: Alstonville, Judy’s Everbearing and Durham’s Emerald. Both qualitative and quantitative GC–MS analyses were performed on their peel solvent extract. The results showed that the unique phe- notypes of finger lime are also correlated to unique molecular compositions. Each cultivar revealed a dif- ferent chemotype: limonene/sabinene for cv. Alstonville, limonene/citronellal/isomenthone for cv. Judy’s Everbearing, and limonene/citronellal/ citronellol for cv. Durham’s Emerald. To the best of our knowl- edge, these chemotypes have never been reported in any other citrus species. Furthermore, the amounts of some volatile constituents (c-terpinene, a-pinene, b-pinene, citral), which are generally the major con- stituents besides limonene in lime species, were surprisingly low in the three cultivars. Comparative GC– MS analysis also showed that some volatile molecules tended to be specific to one cultivar and could therefore be considered as markers. Moreover six molecules were reported for the first time in a citrus extract and confirmed by synthesis. Heart-cutting enantioselective two-dimensional GC–MS was per- formed to determine the enantiomeric distribution of the major chiral constituents. The combined data on three finger lime cultivars gives evidence of their divergence from other citrus species. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The Australian finger lime Citrus australasica is one of five native citrus species endemic to Australia. It is native to the rainforests of South East Queensland and Northern New South Wales. Finger limes are genetically diverse in shape, peel and pulp color, size and taste. All have in common the caviar-like pulp, which makes this fruit unique in the genus Citrus. Because of the increasing demand for finger limes, initially from the restaurant trade, some finger lime cultivars were selected from the wild and are currently commercially grown in Australia. For the time being, one finger lime variety has been registered with Plant Breeders’ Rights (C. aus- tralasica var. sanguinea, also called ‘‘Rainforest Pearl’’), and seven finger lime cultivars have been registered with the Australian Cul- tivar Registration Authority: Alstonville, Blunobia Pink Crystal, Durham’s Emerald, Judy’s Everbearing, Pink Ice, Byron Sunrise and Jali Red. In our previous study (Delort and Jaquier, 2009), the volatile composition of the peel extract of Australian finger lime of unknown cultivar was investigated by gas chromatography– mass spectrometry (GC–MS). The work highlighted a unique com- position (limonene/isomenthone/citronellal). Six new terpenyl esters were identified and their structures confirmed by chemical synthesis. In the present study, three finger lime cultivars, namely Alstonville, Judy’s Everbearing and Durham’s Emerald, were inves- tigated for the first time with the aim of comparing, both qualita- tively and quantitatively, their volatile composition and identifying the molecular markers of the cultivars. 2. Results and discussion 2.1. Comparison of phenotypic and organoleptic characters of fresh fruits As shown in Fig. 1, the different cultivars investigated in the present study were relatively close in terms of shape and size, but differed in their peel and pulp color. The cultivar Alstonville http://dx.doi.org/10.1016/j.phytochem.2014.10.023 0031-9422/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Firmenich SA, Corporate R&D Division, Route des Jeunes 1, CH-1211 Geneva 8, Switzerland. Tel.: +41 22 780 35 32; fax: +41 22 780 33 34. E-mail address: estelle.delort@firmenich.com (E. Delort). 1 Present address: Universidade Federal do Rio de Janeiro, Instituto de Química, Ilha do Fundão, Rio de Janeiro, RJ 21941-909, Brazil. Phytochemistry 109 (2015) 111–124 Contents lists available at ScienceDirect Phytochemistry journal homepage: www.elsevier.com/locate/phytochem