Pumpkin carbonyl compounds

The fruit of pumpkin (Cucurbita pepo) is eaten boiled or baked. About 30 compounds have been identified in the volatile extracts of raw pumpkin, with the major classes of compounds being aliphatic alcohols and carbonyl compounds, furan derivatives and sulfur-containing compounds. Hexanal, ( )-2-hexenal, (Z)-3-hexen-l-ol and 2,3-butanedione have been identified as important for the flavour of freshly cooked pumpkins (Table 7.7) [35] however, studies using GC-O techniques are needed to get a better understanding of the character-impact compounds of pumpkins. 

Pumpkins (Cucurbita pepo) are a member of the family Cucurbitaceae which includes squashes, melons, pumpkins and cucumbers. Pun kins are of New World origin and are believed to have been important in the diet of aboriginal Americans. The flavor composition of the Cucurbits has received little attention though other members of the Cucurbitaceae have been investigated. For exan le, the carbonyl compounds of fresh cucumbers (Cucumis sativus) were studied almost 20 years ago ( ). 

Cucurbituril is a hexameric macrocyclic compound with the formula (C6H6N402)6 shaped like a pumpkin which belongs to the botanical family Cucurbitaceae. This macrocyclic cavitand has idealized symmetry Z>6h with a hydrophobic internal cavity of about 0.55 nm. The two portals, which are each laced by six hydrophilic carbonyl groups, have a diameter of 0.4 nm [Fig. 20.4.8(a)],... 

Almost three-quarters of a century later, this substance was rediscovered by Mock and coworkers [26], With the help of modem instruments they finally characterized it as a hexameric macropolycyclic compound with composition of C36H36N24O12. The X-ray crystal stmcture (Figure 10) of this compound [26] reveals an internal cavity of 5.5 A diameter which is accessible from the exterior by two carbonyl-laced portals of 4A diameter. The cavity of cucurbituril has dimensions equivalent to that of a-CD ( 5.7A). Similar to cyclodextrins the interior of cucurbituril is hydrophobic and therefore, provides a potential site for inclusion of hydrocarbon molecules. Mock et al. proposed a trivial name cucurbituril for this compound because of its resemblance to a pumpkin which belongs to the botanical family Cucurbitaceae. 

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