Chirality in Biology
599
Essential oils have been used in folk
medicine, and it is a common belief
that odors can influence mood, alertness,
and sexual arousal (witness the appeal of
aromatherapy). Some work concerns the
effects of chiral fragrances on the hu-
man autonomic nervous system. In one
study, inhalation of (
+
)-limonene (odor
is orange) gave increased systolic blood
pressure, subjective alertness, and rest-
lessness; inhalation of (
−
)-limonene (odor
is turpentine) increased systolic blood
pressure without influencing psycholog-
ical parameters. Similar responses were
obtained with carvone enantiomers. The
effects were complex and both pharma-
cological and psychological mechanisms
were probably involved.
In studies of linalool enantiomers, differ-
ences in perception and responses elicited
by a sensory test and forehead surface
potential wave measurements were mea-
sured. (
R
)-(
−
)-linalool, administered after
hearing environmental sounds, gave a
favorable impression, and there was a
tendency for the beta wave to decrease.
With (
S
)-(
+
)-linalool, there was an un-
favorable impression and the beta wave
increased. Different and complex results
were obtained following mental work.
These preliminary results showed that
the responses to the two enantiomers de-
pended
,inadd
i
t
ion
,ontasksass
ignedto
the subjects.
Enantio-MDGC-MS has been used in
some human metabolic studies. Methyl-
citric acid, MCA, occurs in body fluids
of individuals with propionic acidemia,
methylmalonic aciduria, or holocarboxy-
lase deFciency. MCA has two chiral cen-
ters; of the four possible stereoisomers,
only the (2
S
,3
R
)and(2
S
,3
S
) diastereoiso-
mers were detected in patients and con-
trols, in proportions varying from about
30 to 70%. The differences may be due to
physiological effects on the citrate synthase
enzyme forming MCA from oxaloacetate
and propionyl-CoA.
3.3
Insect Pheromones
±or chiral insect pheromones, the nature
of the chirality generally has a profound
effect on the observed physiological re-
sponse. Thus, with the female spider sex
pheromone, 3-hydroxybutyric acid, only
the (3
R
) structure is functional. All of the
following situations have been observed:
1. As just noted, activity is present in only
one enantiomer, the other being in-
different (e.g. (
+
)-exobrevicomin, pine
sawfly pheromone) or inhibitory (e.g.
(
+
)-disparlure, (
S
)-
cis
-verbenol).
2. All stereoisomers are active (e.g. gran-
disol, seudenol).
3. Different
species
may
differentiate
enantiomers,
for
example,
(
S
)-(
+
)-
ipsdienol
used
by
Ips
paraconfusus
and
the
R
enantiomer
by
I.
cal-
ligraphus
.
A
more
complex
situa-
tion occurs with scarab beetles. ±or
Anomala
osakana
,
the
female
pro-
duces
the
male
attractant,
(
S
,
Z
)-5-
(1-decenyl)oxacyclopentan-2-one. How-
ever, in
Popillia japonica
the (
R
) enan-
tiomer is attractive to males. These
activities are inhibited by the respec-
tive enantiomers. In Feld tests with
A. osakana
,ca
t
che
so
fma
le
sint
rap
s
baited with the (
S
) enantiomer were
completely inhibited by as little as 5% of
the (
R
) form. The reciprocal behavioral
agonist–antagonist situation provides
a species-speciFc chemical signal with
the use of a single chiral structure. In-
terestingly, these two beetles share a
common habitat in Japan.
