LARVICIDAL ACTIVITY OF EXTRACTS OF CARICA PAPAYA LINN AND DACROYDES EDULIS (G.DON) H.J LAM ON THREE MOSQUITO SPECIES
LARVICIDAL ACTIVITY OF EXTRACTS OF CARICA PAPAYA LINN AND DACROYDES EDULIS (G.DON) H.J LAM ON THREE MOSQUITO SPECIES
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Date
2017-07
Authors
AKANDE-GRILLO, HALIMA TEMI
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Abstract
Mosquitoes are the number one vector involved in the transmission of human diseases responsible for human debility and mortality. Crude extracts of Carica papaya (CP) and Dacryodes edulis (DE) have been indicated as having effects on larval mortality. This work was designed to evaluate the larvicidal activities of three solvent extracts and fractions of the seeds, leaves, stems and roots of both plants against the larvae of Aedes vittatus, Anopheles gambiae and Culex quinquefasciatus by standard methods. A standard method was also adopted to determine the growth inhibitory and acetylcholinesterase inhibitory activities. Their effects on a non-target organism were determined and structural analyses of their active principle(s) by FTIR, GCMS and NMR were carried out. Preliminary studies on the crude extracts at 500ppm showed the ethanol and hexane extracts of the seeds and leaves of CP and DE had significant (p<0.05) larvicidal activites against the larvae of all three species. Extracts with mortality above 70% against at least two of the three species were assayed for their LC50 and LC90 values with concentrations of 6.25-400ppm and showed time-dependant increases in activity at 12h, 24h and 48h. The ethanol extract of the seeds of CP gave LC50 values of 100.00, 62.24 and 262.14ppm at 48h against the larvae of Aedes vittatus, Anopheles gambiae and Culex quinquefasciatus respectively. The corresponding values for the hexane extract of the seeds of CP were 61.47, 111.76 and 264.78ppm. The ethanol and hexane extracts of the leaves of CP gave LC50 values of 93.19 and 48.14ppm against Aedes vittatus while against Anopheles gambiae the values were 40.80 and 29.32ppm. The LC50 values of ethanol and hexane extract of CP against Culex quinquefasciatus were 43.96 and 74.83ppm.The ethanol extract of the seeds of DE had the lower LC50 value of 150.54, 85.99 and 110.18ppm against the larvae of Aedes vittatus,
Anopheles gambiae and Culex quinquefasciatus when compared to the hexane extract of the leaves with values of 1177.00, 1762.10 and 508.28ppm against the three species at 48h. The hexane extract of the leaves of CP and the ethanol extract of the seeds of DE were fractionated using column chromatography and the fractions were tested for larvicidal activity against Aedes vittatus and Culex quinquefasciatus. Carica papaya hexane leaf extract (CPHLE) yielded twelve (12) fractions and fraction 1 had the best larvicidal activity against both species with LC50 values of 10.72 and 15.15ppm while Dacryodes edulis ethanol seed extract (DEESE) yielded seven (7) fractions and fraction 1 (f1) had the best larvicidal activity against both species with LC50 values of 10.48 and 10.16ppm against Aedes vittatus and Culex quinquefasciatus respectively. Phytochemical analyses of the partially purified CPHLE fraction 1 (CPHLE-f1) indicated the presence of carbohydrates, cardiac glycosides and triterpenes while the partially purified DEESE fraction 1 (DEESE-f1) showed the presence of carbohydrates, cardiac glycosides, steroids, triterpenes, tannins and alkaloids. Growth inhibitory activity of the fractions were evaluated on first, second, early third and late third-early fourth instars of both Aedes vittatus and Culex quinquefasciatus larvae. CPHLE-f1 gave inhibition values that increased with age of instar. Acetylcholinesterase inhibition was highest with values >30% at a concentration of 100ppm of CPHLE-f1 against both species while DEESE-f1 had the highest inhibition at 6.25ppm with values >10% against Aedes vittatus and >20% at 12.5 and 25ppm against Culex quinquefasciatus. Effects of the CPHLE-f1 and DEESE-f1 on Poecelia reticulata (guppy fish) showed no significant difference between the mortality of tests and controls. Fourier transform infra-red spectroscopy of CPHLE-f1 showed presence of functional groups for alcohol (O-H), alkane/alkyl (C-H), carbonyl (C=O), nitro compound (N-O) and
alkene (C=C) while that of DEESE-f1 showed the presence of alkane/alkyl (C-H), aldehyde (C=O), nitro compound (N-O), acyl/phenyl (C-O), alkoxy (C-O) and alkene (C=C). Gas chromatography mass spectroscopy analysis of CPHLE-f1 showed the presence of eleven (11) compounds while DEESE-f1 showed presence of seven (7) compounds. Column chromatography of CPHLE-f1 yielded five (5) sub-fractions of which sub-fraction 3 provided the highest larvicidal activity. Further purification of the CPHLE-f1 sub-fraction 3 by gel filtration yielded two bands; fraction 1 and fraction 2 which gave LC50 values of 3.9 and 2.25ppm respectively against Aedes vittatus. Column chromatography of DEESE-f1 yielded four (4) sub-fractions with larvicidal activity between 31.38 and 94.43ppm. Nuclear magnetic resonance of fraction 2 of CPHLE-f1 sub-fraction 3 is suggestive of an eighteen (18) carbon fatty alcohol compound Octa-dec-9-enol. In conclusion, Carica papaya and Dacryodes edulis contain larvicidally active principles against Aedes vittatus, Anopheles gambiae and Culex quinquefaciatus with values that suggest their candidacy for field trials.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY IN PARTIAL FUFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DOCTOR OF PHILOSOPHY OF SCIENCE (PH.D.) IN BIOCHEMISTRY DEPARTMENT OF BIOCHEMISTRY, FACULTY OF LIFE SCIENCES AHMADU BELLO UNIVERSITY ZARIA, NIGERIA
Keywords
LARVICIDAL ACTIVITY,, EXTRACTS,, CARICA PAPAYA LINN,, DACROYDES EDULIS,, H.J LAM,, THREE MOSQUITO SPECIES