10 0 - EleA@UniSA - Università degli Studi di Salerno

Polygodial
hot tastig
CHO
CHO
FIGURE 1.23
Isotadeonal
not active
CHO
CHO
Anyway this structural feature is not enough to explain why other molecules like
scalaradial, having an ,-unsaturated dialdehyde moiety with the correct
stereochemistry, are not active. The lack of activity is probably related to the
size of the molecule: too big to interact with the receptors.
The isolation from Cacospongia mollior, of desacethyscalaradial .resulted hot
tasting, pointed out that a presence of a free hydroxyl group in the framework
can increase the activity toward receptors.
Furthermore, in other cases, it has been shown that presence of a polar group
can decrease dramatically the activity, such as in the case of both
isovelleraloids , merulidial and its analogues.
In fact, some studies carried out to evaluate pungency amount of some
unsaturated dialdehydes on the human tongue and their affinity for specific [ 3 H]-
resiniferatoxin binding sites in rat spinal cord, showed that the hydroxyl group
(see derivatives 1.43-1.44a,b) in isovelleral 1.4 and merulidial 1.31 decreases
highly the affinity of these compounds for [ 3 H]-resiniferatoxin 1.45 binding sites.
(Figure 1.24)
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