Assessment on diversity and bioactive compounds present in endophytic fungi isolated from Rhizophora mucronata in Matang Mangrove Forest Reserve, Perak, Malaysia
Rhizophora mucronata is an important ecosystem entity of the Malaysian mangrove forest. Because the tree grows in an extreme environment, any organism that is isolated from this tree is of huge interest due to its potential in having novel bioactive compounds. This study aimed to assess endoph...
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| Format: | Thesis |
| Language: | English |
| Published: |
2018
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/75816/1/FH%202018%2017%20-%20IR.pdf http://psasir.upm.edu.my/id/eprint/75816/ |
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| Summary: | Rhizophora mucronata is an important ecosystem entity of the Malaysian
mangrove forest. Because the tree grows in an extreme environment, any
organism that is isolated from this tree is of huge interest due to its potential
in having novel bioactive compounds. This study aimed to assess endophytic
fungal diversity isolated from mangrove plant, R. mucronata, to evaluate the
bioactivities exhibited by selected fungal endophytes, and to isolate and
identify compounds associated with the selected endophytic fungi extracts.
In the present work, a total of 78 fungal isolates were isolated, identified and
characterized from the leaf tissues of R. mucronata. All strains were
identified using primer internal transcribed spacer 1 (ITS1) and internal
transcribed spacer 4 (ITS4). The DNA sequences of the strains recorded
high similarities to their respective species in the GenBank. Phylogenetic
trees were constructed and analyzed using Maximum Likelihood (ML) criteria
together with 78 mangrove endophytic fungal sequences and 117 additional
sequences of fungal species incorporated from the GenBank. Most of the
dominating fungal endophytes were from the genus Pestalotiopsis, followed
by Alternaria and Cladosporium. Six isolates representing the genera
Alternaria, Fusarium, Nigrospora, Pestalotiopsis, Phoma, and Xylaria, were
screened for their antagonism activities. The antagonism tests were
evaluated through dual culture and non-volatile compound assay. Dual
culture test assay revealed their inhibition percentages against the
phytopathogenic fungus Fusarium solani between 49-69%, and 1-25% when
using non-volatile test assay. The fungal isolates were further screened for
their antibacterial activities against four pathogenic bacteria, Bacillus subtilis,
Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Of
the six isolates, only Fusarium lateritium and Xylaria sp. showed antibacterial
activities against tested bacteria, with the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) ranging from 0.5 to 2
mg/mL. The 1,1-diphenyl-2-picrylhydrazyl(DPPH) radical scavenging assay
recorded antioxidant activity in Xylaria sp. with 3-fold higher when compared
to F. lateritium.
The chemical constituents of F. lateritium and Xylaria sp. were determined
via Gas Chromatography (GC) with Mass Spectrometry (MS) and Flame
Ionization Detector (FID). These two fungal species were chosen based on
their positive activities in several assays conducted in the previous section
before, including, antagonism, antibacterial and antioxidant assay. Overall,
69 compounds were identified from ethyl acetate and hexane extracts of F.
lateritium and Xylaria sp..Compounds such as phenylethyl alcohol,
phenylacetic acid, cetene, and 2,4-Ditert-butylphenol, were commonly found
in all the extracts of both fungal species. Variations of constituents were
found in all extracts for both fungal isolates. Hexane extracts of F. lateritium
and Xylaria sp. both recorded a greater variation in chemicals identified.
While there were almost similar compounds identified from ethyl acetate
extracts of both fungal isolate. Evaluation on the biological activities
exhibited by F. lateritium and Xylaria sp. before, with the presence of these
compounds, proved that these two fungal isolates have great potential as
antimicrobial agents. Screening the endophytic fungal community associated
with Rhizophora mucronata, and bioactivities exhibited by the selected
isolates has proved that mangroves endophytic fungi could be a potential
source in finding the bio-control agent and another important source for vital
bioactive compounds. |
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