Estudo fitoquímico e alelopático de extratos de Diaporthe phaseolorum
Abstract
Endophytic fungi have the ability to live inside or outside a plant tissue, without
harming it. Studies have shown that these groups of fungi are promising sources in the
search for new natural compounds, since in many of them, antifungal, antibacterial,
antioxidant and phytotoxic activities were found, being of great interest for applications
in medicine, agriculture and chemical biology. In this work, the fungus Diaporthe
phaseolorum, extracted from healthy leaves of Serjania lethalis A.St-Hils, a liana
belonging to the Sapindaceae family commonly found in the Brazilian cerrado, was
used. already published. Fungi of the genus Diaporthe, whose asexual state is known as
Phomopsis, are found as endophytic and saprophytic in a variety of plant species, and
produce compounds with known phytotoxic and cytotoxic activities, such as
gulypyrones and phomoxanthones, but there are still few studies with the species
Diaporthe phaseolorum. Therefore, the main objectives of this work were to evaluate
the phytotoxic potential of extracts and fractions of D. phaseolorum on indicator and
invasive target species, analyzing their mode of action, as well as identifying secondary
metabolism compounds. First, two extracts were prepared, one mycelial (EME) and the
other from the culture medium (EMC), extracted with ethanol and ethyl acetate by
liquid-liquid partition, respectively. Both extracts were tested in bioassays that
evaluated the growth of wheat coleoptile (Triticum aestivum L.), germination and
seedling growth of mono and eudicotyledonous invasive and indicator species: wild
poinsettia (Euphorbia heterophylla L.), colony grass (Megathyrsus maximus J.), onion
(Allium cepa L.) and sesame (Sesamum indicum L.), respectively, and were also tested
in a bioassay that evaluates the growth of sesame (Sesamum indicum L.) root
metaxylem cells. The extracts were fractionated on a silica column in normal phase and
their respective fractions were again tested on the growth of wheat coleoptiles in order
to select those with greater phytotoxicity. Taking into account the results and yields,
fraction 9 (EME9) from the mycelial extract (EME) was selected for the seedling
growth and germination bioassays and for the sesame root metaxylem cell growth
bioassay. Both crude extracts (EME and EMC) used in the wheat coleoptile growth
bioassay were able to inhibit their growth, showing their highest percentages of
inhibition when used at their highest concentrations (0.8mg/mL-1
), as the fractions
EME9 and EME3 from the crude mycelial extract were those with the highest inhibitory
percentages for the same bioassay. In the seedling growth bioassay, the crude extract
(EME) and its fraction (EME9) were able to inhibit the growth of both aerial parts and
roots of wild poinsettia seedlings. Wild poinsettia was also more sensitive to mycelial
extract and its fraction in relation to germination percentage, showing the lowest
percentage values. The growth of sesame seedling root metaxylem cells was also
inhibited, proving the phytotoxic effect of the mycelial extract and its respective
fraction to them. Through a chemical analysis by CLUE (ultra-efficiency liquid
chromatography) performed on samples EMC, EME and EME9, 7 major compounds
were identified, all already described in the literature for the genus Diaporthe, where the
compound fomoxantone A is the one to be present in larger quantity and in all analyzed
samples. The crude extracts EMC and EME and the EME9 fraction showed phytotoxic
activity in the bioassays performed in this study, inhibiting the growth of wheat
coleoptiles, roots and aerial parts of the target species and sesame root metaxylem cells.
Thus, compounds identified in the extracts of Diaporthe phaseolorum show promise in
the study of their bioactivities, since studies with the species related to this bioactivities
are scarce in the literature.
Collections
The following license files are associated with this item: