Biology Reference
In-Depth Information
threats not only to the health of crops, but
also to animals and humans ingesting con-
taminated feeds and foods.
An ethanolic extract of aerial parts of
Z. punctata
was active toward fungal patho-
gens isolated from soybean carpels and seeds:
Phomopsis longicolla, Alternaria alternata,
Fusarium equiseti
and
Colletotrichum trun-
catum;
one isolate of
Sclerotium bataticola
obtained from the stem and four isolates of
Fusarium graminearum
were also evaluated
(Svetaz
et al
., 2004). Fungi were character-
ized by the morphology of their colonies,
fruiting bodies and spores. The application
of different techniques of fractionation with
solvents (n-hexane, CHCl
3
and n-BuOH)
allowed the separation of three extracts.
The CHCl
3
fraction was chromatographed on
Silica Gel 60H eluted with different solvents.
Two known chalcones, 2¢,4¢-dihydroxychal-
cone and 2¢,4¢-dihydroxy-3¢-methoxy-chalcone,
and the flavanone 7-hydroxyflavanone were
purified together with two new components,
1-methyl-3-(4¢-hydroxyphenyl)-propyl caffeate
and 1-methyl-3-(3¢,4¢-hydroxyphenyl)-propyl
caffeate. Antifungal evaluation of the extracts
and purified substances were performed
with agar dilution assays (Mitscher
et al
.,
1972; Zacchino
et al
., 1999). MIC (defined
as the lowest concentration of extract or
pure compound showing no visible fungal
growth) was determined for each extract
and for the purified compounds and com-
pared with antifungals of commercial use
(strobirulines pyraclostrobin, azoxystrobin,
carbendazin and ketoconazole). Among the
isolated substances chalcones have a potent
antifungal action; the flavones and one
of the new compounds (1-methyl-3-(4¢-
hydroxyphenyl)-propyl caffeate) have a
moderate activity; and 1-methyl-3-(3¢,4¢-
hydroxyphenyl)-propyl caffeate did not
show significant activity up to a value of
50 mg of compound/ml. Taking into account
that extracts and pure compounds with MIC
values >1000 or >50 mg/ml, respectively,
were considered inactive (Svetaz
et al
.,
2004), it is interesting to note that four of
the five compounds isolated from the chlo-
roform extract displayed good activity (MIC
≤6.25 mg/ml) against
P. longicolla
growth,
the fungus that produces serious seed decay
digits followed by the prime sign (¢).) The B
ring, however, is fairly unsubstituted. These
types of compound are especially found in
Fabaceae.
12.4.2
Antifungal activity
Fungi occur ubiquitously and are well
adapted to use a wide range of substrates as
their carbon, nitrogen and energy sources.
These organisms can cause serious diseases
in plants, animals and humans. Ethanolic
extracts of leaves and twigs of
Z. punctata
showed fungicidal action against yeasts
(
Saccharomyces carlsbergensis
and
Rhodo-
torula
spp.), wood-rot causing Basidiomy-
cetes (
Rhodotorula
spp.,
Lenzites elegans,
Pycnoporus sanguineus
and
Schizophyllum
commune
) and some phytopathogenic fungi
(
Fusarium oxysporum, Penicillium notatum,
Trichoderma
spp. and
Aspergillus niger
)
(Quiroga
et al
., 2001). The
in vitro
biological
activity of the alcoholic plant extracts was
assessed on the basis of the hyphal radial
growth rate of filamentous fungi and the
growth rate of yeasts in the presence and
absence of the plant extract. Growth of fila-
mentous fungi was inhibited 40-80% in the
presence of 0.8 mg of dry extract/ml of cul-
ture medium. The effect on yeast growth
was evaluated by the agar well diffusion
assay and paper disc diffusion assay (Camm
et al
., 1975; Cole, 1994; Torres
et al
., 1998)
and MIC was determined by broth dilution
test. MICs against
S. carlsbergensis
and
Rhodotorula
spp. determined by dilution
tests were 400 and 200 mg of dry extract/ml,
respectively. Data indicated that the extracts
of
Z. punctata
have a considerable
in vitro
antifungal activity against all filamentous
fungi and yeasts. It is worth noting that some
members of the
Aspergillus
and
Fusarium
genera are well-known producers of aflatox-
ins. These secondary metabolites are potent
carcinogens, hepatotoxins, teratogens and
inmunosuppresive compounds (Ciegler,
1975).
F. oxysporum
produces phytotoxic
fusaric acid and lycomarasmin (Ueno
et al
.,
1977).
A. niger
produces potent mycotoxins
on foodstuffs and is the most prevalent fun-
gus affecting maize. These fungi represent
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