International Journal of Aquaculture, 2017, Vol.7, No.18, 122-127
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4.7 Phytochemical screening
4.7.1 Detection of saponins
a) Froth test: Extracts of 5 g were diluted with distilled water to 20 ml and this was shaken in a graduated cylinder
for 15 minutes. Formation of 1 cm layer of foam indicates the presence of saponins.
b) Foam test: Extract of 0.5 g was shaken with 2 ml of water. If foam produced persists for ten minutes it indicates
the presence of saponins.
4.7.2 Detection of phenols ferric chloride test
Extracts were treated with 3-4 drops of ferric chloride solution. Formation of bluish black colour indicates the
presence of phenols.
4.7.3 Tannins
Extract of 0.1 g was taken up in 10 ml distilled water and filtered. Then a few drops of ferric chloride (Fecl
3
)
reagent were added to 1 ml of the filtrate. The mixture was observed for the formation of blue, blue-black, green
or green-black colouration or precipitate.
4.7.4 Detection of flavonoids
Alkaline reagent test: Extracts were treated with few drops of sodium hydroxide solution. Formation of intense
yellow colour, which becomes colourless on addition of dilute acid, indicates the presence of flavonoids.
4.7.5 Glucosinolates
Extract of 0.1 g was dissolved in 5 ml of chloroform followed by filtration as described by Adeoye and Oyedapo
(2004) method. Concentrated tetraoxosulphate (vi) acid (Sulphuric acid) was carefully layered at the bottom of the
tube without disturbing the solution. It was observed for the formation of a sharp brown ring at the
chloroform/sulphuric acid interface.
4.7.6 Test for triterpenes and steroids
The Salkowski test: Extract of 1 g was warmed in 5 ml of chloroform for 30 minutes. The chloroform solution
was then treated with a small volume of concentrated tetraoxosulphate (vi) acid (H
2
SO
4
) and shaken. The red
colour produced within a few minutes indicated a positive reaction.
4.7.7 Detection of proteins and amino acids
Xanthoproteic test: The extracts were treated with few drops of conc. Nitric acid. Formation of yellow colour
indicates the presence of proteins.
4.8 Statistical analysis
The microbial load of fish tissue (skin, gills, intestine and liver) and antimicrobial and antifungal activities
(diameter of zone of inhibition, mm) of soursop leaves against tested pathogens resulting from the experiment
were subjected to one way analysis of variance (ANOVA) using SPSS (Statistical Package for Social Science
version 15.0).
5 Conclusion
The result of the present study showed that
A. muricata
leaves had antimicrobial properties and it is therefore
suggested that aqueous, methanolic and ethanolic extracts of soursop leaves can be used in fish culture as
alternative to conventional vaccines, synthetic antibiotics and chemotherapeutic agents. The use of
A. muricata
leaves extracts as natural antimicrobial agents in fish culture system may be environmentally friendly, fully
biodegradable, safe and non-toxic (toxin binders), effective against a number of opportunistic pathogens and no
resistant problems.
Authors’ contributions
This work was carried out by three authors. Authors OSE, FS and OIB designed the study and wrote the protocol, authors OSE and
FS supervised the study. Author OIB performed the experiment and the statistical analysis as well as managed the literature searches.
