Introduction: Fish has always been an important part of the human diet due to its natural availability and nutritional value. With the advent of population growth, the consumer demand for fish has exponentially increased. To meet increasing demand, new methods such as netting, spearfishing, angling, and trapping were developed in Africa for catching fish. In established modern fishing fleets, these methods are well-regulated to avoid overfishing as well as consideration for sustainability and environmental impact. Sphenostylis marginata is a plant in the family Fabaceae and native to many parts of Africa. It is used as a wild vegetable, in folk medicine, as a fetish plant, food additive, and for harvesting fish. Small-scale fishermen in selected parts of Zambia use the crushed roots of this plant to harvest fish for consumption. Published data suggest that phytochemicals present in fish toxins and the lethal concentration have a major role to play in the ability of fish to utilize dissolved oxygen. Phytochemical screening and lethal concentration (LC50) of fish toxins are the initial tests required to discover their bioactive profile and short-term poisoning potential.
Objective: To determine the effects of S. marginata on dissolved oxygen consumption rate in Oreochromis
niloticus fingerlings.
Materials and Methods: An interventional approach was used
to determine the effects of different concentrations of the aqueous root
extract of S. marginata on dissolved
oxygen consumption rate (DOCR) in Oreochromis niloticus fingerlings. The fresh
root of S. marginata was collected
from the Muchinga escarpment in the Mpika district of Zambia, while the crude
stem methanol extract of the positive control Albizia versicolor was collected
from the University of Zambia’s Biology department. The studied plant was
examined, identified, extracted, and concentrated using the Yamato DC401/801
Neo Cool freeze drier. Phytochemical screening was carried out, and toxicity
studies were performed to establish the LC50. Dissolved oxygen was measured
using a calibrated 86031 AZ waterproof IP67 combo water quality tester for O.
niloticus fingerlings in the presence of S.
marginata and the positive control. Dissolved oxygen results were used to
calculate dissolved oxygen consumption rates. Comparisons of dissolved oxygen
consumption rate results between the study plant and the positive control were
made using a two-sample t-test for unequal variances in IBM SPSS Statistics
version 20. Analysis of variance (ANOVA) of temperature, salinity, and pH for
both plants was performed. P values less than 0.05 were considered
statistically significant. The Least Significant Difference (LSD) was used as a
post hoc test to determine where the differences lie in statistically
significant results.
Results: Phytochemical screening of S. marginata revealed the presence of alkaloids, saponins, sterols,
flavonoids, tannins, and glycosides. From experimental results, 200 mg/L of S. marginata was required to cause
mortality in 50% of O. niloticus in 3 hours (LC50). Calculations from the
arithmetic method of Karber showed the LC50 of 210 mg/L, while graphical
approximations using RS statistical software estimated a lethal concentration
of 221.6 mg/L at ± 15.4 standard error with lower and upper limits of 186.1 and
257.2, respectively. Fingerlings mortality increased with the increase in
concentration of the extract, accompanied by induced behavioral changes like
rapid swimming, gasping for oxygen, vertical swimming, and loss of balance. The
study plant affected the ability of O. niloticus fingerlings to utilize
dissolved oxygen in a concentration-dependent response, and the mean dissolved
oxygen consumption rate of S. marginata was
significantly lower than the positive control A. versicolor (-0.7075 mg/L/hr.
and -0.2675 mg/L/hr, respectively). Both plant did not affect the solution
parameters pH, temperature, and salinity.
Conclusion: In conclusion, the root extract of S. marginata affects the ability of O.
niloticus fingerlings to utilize dissolved oxygen with a characteristic
concentration-dependent response. The plant does not affect pH, temperature,
and salinity. S. marginata contains
the phytochemicals tannins, saponins, sterols, flavonoids, alkaloids, and
glycosides, highlighting its potential for exploitation as a
cholesterol-lowering, antitumor, antimicrobial, promoting wound healing, and
anti-diabetic.
Author (s) Details
Brian Mukuka
Faculty of Health Sciences, Chreso University, P.O. Box 37178, Lusaka
10101, Zambia.
James Nyirenda
Department of Chemistry, University of Zambia, P.O. Box 32379, Lusaka
10101, Zambia.
Rehana Omar
Department of Physiological Sciences, University of Zambia, P.O. Box 50110,
Lusaka 10101, Zambia.
Mony Narayani
Faculty of Health Sciences, Chreso University, P.O. Box 37178, Lusaka 10101,
Zambia.
Gibson Sijumbila
School of Medicine, Mulungushi University, P.O. Box 80415, Lusaka 10101,
Zambia.
Please see the book here:- https://doi.org/10.9734/bpi/cbrp/v5/5068
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