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concerted action of microbial cells (quorum
sensing), as, for example, a general induc-
tion of anabiosis (Mulyukin
et al
., 2001).
Although atractive, the hypothesis of chem-
ical signalling mediated by ARs needs fur-
ther research, especially because soil abiotic
factors can affect the integrity of AR mol-
ecules (e.g. by complexation or oxidation)
before exerting their action on receptor
organisms, avoiding the process of signal
delivery (Kamnev
et al.
, 2009).
growing in South America, commonly
known as 'chichita' or 'molle Córdoba' in
Argentina. Its leaves are used by rural peo-
ple as an anti-arthritic, haemostatic, diu-
retic and tonic, and in the treatment of
respiratory diseases. As occurs with other
Anacardiaceae species, phenolic lipids in
L. molleoides
, as well as in the related
species
Lithraea brasiliensis
, were responsi-
ble for allergic contact dermatitis caused by
catechol-type compounds rather than ARs
(López
et al.
, 2005). This plant is a source of
1,3-dihydroxy-5-(tridec-4
¢
,7
¢
-dienyl)benzene,
an AR derivative that induces apoptosis in
human tumoural cell lines (Barbini
et al.
,
2006).
Lithraea caustica
, commonly known as
'litre', is an endemic Chilean species of the
same genus (Russo
et al.
, 2009). Its stem juice is
used for cough treatment. Litreol, the active
compound identified from their leaves, has
been shown to be a 3-[pentadecyl-10-enyl- cat-
echol] instead of an AR. This lipid phenolic
inhibits cancer cell viability in a dose-dependent
manner and induces apoptotic cell death at
0.59-1.18 mM. Another Anacardiaceae, the
Mexican
Amphipterygium adstringens
, is tra-
ditionally used in the treatment of gastritis and
ulcers (Castillo-Juarez
et al.
, 2007). It contains
alkylphenolic acids (C15:0, C16:0, C17:0 and
C19:0) in its bark. These compounds showed
potent activity against
Helicobacter pylori
, the
major etiological agent of chronic active gas-
tritis and peptic ulcer disease, linked also to
gastric carcinoma. The leaves of a Mexican
Myrsinaceae,
Stylogyne turbacensis
, contain
5-[11
¢
(
S
)-hydroxy-8
¢
-heptadecenyl]resorcinol
and 5-[12
¢
(
S
)-hydroxy-8
¢
,14
¢
-heptadecadienyl]-
resorcinol (Jimenez Romero
et al.
, 2007). These
compounds showed a strong activity in the
leishmania assay at 7 and 3 mM, respectively.
The 5-[12
¢
(
S
)-hydroxy-8
¢
,14
¢
-heptadecadienyl]-
resorcinol showed moderate activity against
a drug-resistant strain of
Trypanosoma cruzi
with an IC
50
value of 22 mM. The cushion herb
Oxalis erythrorhiza
(Oxalidaceae) is known
as 'boldo de la cordillera' in the San Juan
province of Argentina. A decoction of the
aerial parts is recommended for hepatic
and heart ailments (Feresin
et al.
, 2003). The
aerial parts contain 3-heptadecyl-5-methoxy-
phenol and the lipidic quinone embelin.
The former compound was active against
10.7.5
Phytoanticipin role
The fungicide, fungistatic and bacteriocide
activities of ARs together with their consti-
tutive expression in plants suggest a phy-
toanticipin function for these molecules
(Kozubek and Thyman, 2005). The highest
concentrations of ARs are in seedlings and
young tissues but are also high during the
entire plant growth. Glycosylated ARs may
be produced in plant tissues to avoid auto-
toxicity and/or to facilitate transport into
the plant or release to the environment. As
observed for other phytoanticipins, the bio-
synthesis of ARs also can be increased by
wounding, exposition to chemicals and
biotic stimuli. Experiments
in vivo
on rye
coleoptiles showed that the infection of the
seedlings with
Fusarium culmorum
signifi-
cantly increased the level of plant ARs
(Kozubek
et al
., 2001). Treatment of cereal
grains with exogenous resorcinolic lipids
results in increased plant resistance to vari-
ous phytopathogenic fungi. These observa-
tions
suggest
that
ARs
participate
in
host-pathogen relationships.
10.8 ARs and their Derivatives
Isolated from Medicinal Latin
American Plants
With the exception of the cashew nut,
reports on the isolation, identification and
characterization of ARs from cultivated or
medicinal Latin American plants are scarce
and often involve AR derivatives. For exam-
ple,
Lithraea molleoides
is a tree naturally
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