Quince, fruit

Fleischmann, R, K. Studer et al. (2002). Partial purification and kinetic characterization of a carotenoid cleavage enzyme from quince fruit (Cydonia oblonga). J. Agric. Food Chem. 50(6) 1677-1680. 

Silva BM, Andrade PB, Ferreres F, Domingues AL, Seabra RM and Ferreira MA. 2002. Phenolic profile of quince fruit (Cydonia oblonga Miller) (pulp and peel). J Agric Food Chem 50(16) 4615—4618. 

Orenes-Pinero E, Garcia-Carmona F and Sanchez-Ferrer A. 2005. A kinetic study of p-cresol oxidation by quince fruit polyphenol oxidase. J Agric Food Chem 53(4) 1196-1200. 

Cydonia sinensis Thou. (Syn. Chaeomeles sinensis) Xuan Mu Gua (Quince) (fruit) Vitamin C, malic acid, tartaric acid, citric acid, hydrocyanic acid.49 As astringent in diarrhea, analgesic in arthralgia, gout, cholera. 

Several volatile C.- norisoprenoids have previously been identified in steam-distilled quince fruit oil, in which they are regarded to contribute to the overall flavor impression. These include isomeric theaspiranes, various bicydononane derivatives, 3,4-didehydro- 3-ionol, and isomeric megastigmatrienones and theaspirones (4,5). This report concerns the identification of additional norisoprenoids and their natural precursors in quince fruit. 

Upon employing the more rigorous simultaneous distillation-extraction (SDE) technique (100°C pH 3.7) to isolate the quince fruit volatiles, the resulting aroma composition distinctly differed from that obtained by HVD/SE. After SDE the hydrocarbon 5, the bicyclic alcohol 6 and 3,4-didehydro-(B-ionol (7) were identified as... 

Dienones 12A-12D were also detected as trace components in quince fruit volatiles after SDE sample preparation. However, as shown in Figure 3, except for the low amount of hydrocarbon 5, the distribution of thermal degradation products from 8 did not correspond to the composition of the major norisoprenoids 5-7 obtained after SDE of quince fruit juice. Consequently, diol 8 had to be excluded as their precursor. 

In a further series of experiments, model reactions to thermally-degrade 3-hydroxy-(5-ionol (9) were carried out. The results of these studies are represented in Figure 4. In these model reactions, compounds 5, 6 and 7 as well as unidentified isomers of 5 and 6 were all found in amounts very similar to the natural quince flavor composition obtained by SDE conditions. However, as shown in Figure 4, additional products were found comprising the megastigmatrienols 13, 14 and the tentatively-assigned bicyclic alcohol 15. These latter compounds were not detectable in quince fruit juice. Thus, the diol 9 came under question as a possible precursor. 

One explanation for this surprising result is that the diol 9 is present in quince fruit in both the free and bound forms. To verify this, the glycosides in quince fruit were isolated by XAD... 

Among the aglycones shown in Figure 6, 3-oxo-ot-ionol (19) played a role as a precursor of other C. norisoprenoids detected in quince fruit after SDE sample isolation. As outlined in Figure 7, the keto-alcohol 19 is known to be degraded to the isomeric megastigma-trlenones 23A-23D and 24A/24B (16,17) after thermal treatment under acidic conditions. 

Figure 5. Major volatiles formed from glycosidic extract from quince fruit after SDE treatment (100°C pH 3.7). 5, 6, 7 cf. Fig. 4 16 = marmelo ether 17 marmelo lactone.

Figure 6. Structures of aglycones released from quince fruit extract after glycosidase (emulsin) treatment. 9 - 3-hydroxy-0-ionol 18 3-hydroxy- 3-ionone 19 > 3-oxo-o-ionol 20 = 3-hydroxy-7,8-dihydro-P-ionol 21 vomifoliol 22 = 7,8-dihydrovomifoliol.

Another C., norisoprenoid aglycone in quince fruit, 7,8-dihydrovomi-foliol (22) (cf. Figure 6), can be considered to be the precursor of theaspirones, which were previously found in steam-distilled quince fruit oil (4). As outlined in Figure 8, a synthetic sequence from ot-ionone via dehydrovomifoliol (25) and vomifoliol (21) leads to 7,8-dihydrovomifoliol (22), from which the isomeric theaspirones 26A/26B are formed after thermal treatment (18). 

In the case of the C]j-isoprenoids, it is noteworthy that attractive aroma compoimds were foimd to be derived from the central part of the carotenoid chain which remains after the cleavage of the C j-endgroup. Examples are the key flavor compoimds of quince fruit, i.e. marmelo oxides and marmelo lactones (76). 

In mutants blocked in ABA-ald to ABA conversion, the substrate, ABA-ald, does not accumulate, but it is reduced and isomerized to t-ABA-alc which accumulates at high levels [82]. The glucoside of r-ABA-alc has been isolated from quince fruit [83], the abal mutant of N. plumbaginifolia [84], and the aba3 mutant of Arabidopsis [72] (Fig. 3). 

At this point neither the origin of compounds 1-4 in elephant urine, nor their role, if any, in chemical signaling among elephants is clear. It is noteworthy that in a previous study of the isolation of volatiles from quince fruit, high vacuum distillation/extraction followed by GC-MS yielded different results if one started with homogenized fruit at its natural pH (3.7), versus homogenate at pH 7 to which an enzyme inhibitor had been added. Specifically, the pH 3.7 sample evidenced large amounts of the theaspiranes, but the pH 7 sample showed only trace amounts (Winterhalter et al., 1987). 

Forni, E., Penc,i M. Polesello, A. (1994). A preliminary characterization of some pectins from quince fruit Cydonia oblonga Mill) and pickly pear Opuntia ficus indica) peel. Carbohydrate polymers, 23, 4, 231-295. 

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