MOSQUITO LARVICIDAL PROSPECTS OF TERMINALIA CATAPPA (L.) AND TAMARINDUS INDICA (L.) SEED EXTRACTS IN LABORATORY AND FIELD BIOASSAYS
MOSQUITO LARVICIDAL PROSPECTS OF TERMINALIA CATAPPA (L.) AND TAMARINDUS INDICA (L.) SEED EXTRACTS IN LABORATORY AND FIELD BIOASSAYS
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Date
2016-03
Authors
DAWUDA, Kabadiya Diana
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Abstract
Phytochemical characteristics of petroleum ether extracted seeds of the Indian almond, Terminalia catappa (L.) (Combretaceae) and the tamarind, Tamarindus indica (L.) (Fabaceae) for their larvicidal prospects against third instar larvae of Aedes aegypti, Aedes vittatus and Culex quinquefasciatus species of mosquito were evaluated under laboratory and simulated field conditions. Dried seeds of both trees were pulverised and extracted with petroleum ether (60 - 80°C) in a Soxhlet apparatus. Physicochemical characteristics of the seed oils were determined using standard protocols. Gas Chromatography - Mass Spectroscopy (GC-MS) was used to characterise the phytochemicals contained in the oils. Distilled water diluted extracts of the seeds at separate triplicate treatment concentrations of 0mL/L (control), 0.5mL/L, 1mL/L, 2mL/L, 4mL/L and 8mL/L were each tested on 25 triplicates (n=75) of each larval species for 24 hours under both conditions. Larval mortality was determined thereafter and the data was subjected to ANOVA to test for treatment based significant differences in mean larval mortality, and to determine species specific median lethal concentrations (LC50). Seed oils' acid values, percentage free fatty acids, peroxide values and refractive indices of 16.60mgKOH/g, 8.41mgKOH/g, 12.88meq/kg fat and 1.48 respectively in T. indica were significantly (p < 0.05) higher than the 10.66mgKOH/g, 5.33mgKOH/g, 9.27meq/kg fat and 1.46 respectively in T. catappa. However, the iodine value (39.35meq/kg fat) of T. catappa seed oil was significantly (p < 0.05) higher than the 16.18meq/kg fat value of T indica seed oil. There was no significant (p > 0.05) difference between the saponification values of 162.75mL/kg and 187.94mL/kg for T. catappa and T. indica seed oils respectively. Sixteen metabolites of mainly saturated and unsaturated fatty acids
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including pentadecanoic acid (8.57%), linolelaidic acid (15.30%), elaidic acid (9.15%), stearic acid (5.09%), ricinoleic acid (1.52%), eicosenoic acid (2.83%), eicosanoic acid (2.82%) and heneicosanoic acid (8.77%) were detected in the seed oil of T. indica. Fourteen metabolites of mainly saturated and unsaturated fatty acids including hexadecanoic (palmitic) acid (13.36%), linolelaidic acid (9.97%), oleic acid (11.02%), stearic acid (5.83%) and eicosanoic (arachidic) acid (0.66%) were detected in the seed oil of T. catappa. Terminalia. catappa seed oil caused significantly (p < 0.05) highest larval Ae. aegypti mortality of 81% and 55% and LC50 values of 4.840mL/L and 10.884mL/L; highest larval Ae. vittatus mortality of 53% and 45% and LC50 of 11.143mL/L and 9.099mL/L; highest larval Cx. quinquefasciatus mortality of 91% and 80% and LC50 of 2.275mL/L and 3.055mL/L, under laboratory and simulated field conditions respectively. Tamarindus indica seed oil caused significantly (p < 0.05) highest larval Ae. aegypti mortality of 99% and 95% and LC50 values of 1.248mL/L and 1.359mL/L; highest larval Ae. vittatus mortality of 60% and 76% and LC50 of 4.842mL/L and 1.191mL/L; highest larval Cx. quinquefasciatus mortality of 95% and 100% and LC50 of 0.690mL/L and 0.625mL/L, under laboratory and simulated field conditions respectively. Tamarindus. indica extract was a better larvicidal agent against the three mosquito species than T. catappa. Seed extracts of both trees could thus be adopted in mosquito control operations.
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A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF MASTER OF SCIENCE DEGREE IN BIOLOGY DEPARTMENT OF BIOLOGICAL SCIENCES, FACULTY OF SCIENCE, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA MARCH,
Keywords
MOSQUITO LARVICIDAL,, TERMINALIA CATAPPA,, TAMARINDUS INDICA,, SEED EXTRACTS,, FIELD BIOASSAYS,