BIOASSAY- GUIDED ISOLATION AND CHARACTERIZATION OF A TRYPANOCIDEFROMMISTLETOE (VISCUM ALBUM) EXTRACTS
BIOASSAY- GUIDED ISOLATION AND CHARACTERIZATION OF A TRYPANOCIDEFROMMISTLETOE (VISCUM ALBUM) EXTRACTS
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Date
2023-06
Authors
WASSAGWA, JOHN
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Abstract
Viscum album is a parasitic plant of immense medicinal significance and was evaluated for
antitypanosomal potential. Fresh leaves and stemof V. albumwas obtainedfrom the
following host plants;Azadirachta indica, Psidium guajava, Acacia albida, Khaya
senegalensis and Moringa oleifera. The extracts were prepared by cold maceration using
methanol. In vitro anti-trypanosomal screening of the extracts against T. b. brucei was
carried out in 96 well microtiter plates at final concentrations of 0.8, 0.4, 0.2, 0.1 and 0.05
mg/mL. A bio-assay guided isolation of the active compound was carried out by repeated
silica gel column chromatography, monitored by TLC. Structuralelucidation wasperformed
by 1D and 2D NMR. The LD50 of HDN-one was evaluated in mice using OECD method.
Body weights of mice were taken daily for two weeks and clinical signs of toxicity were
observed. In vivo effect of the compound isolated was evaluated on Trypanosoma
bruceibrucei infected mice. The results showed that leaves and stem of V. album harvested
from A. albida and A. indica hadin vitro activity against Trypanosoma brucei brucei.
Leaves and stem of V. album from A. albida had 75% and 57.50% inhibition respectively
while leaves and stem of V. album from A. indica had 61.21% and 59% respectively.
Viscum album leaves from A. albida had the highest anti-trypanosomal activity (IC50 = 0.30
mg/mL). Qualitative phytochemicalscreening of the methanol extract ofV. album leaves
from A. albida showed the presence of alkaloids, tannins, saponins, anthraquinone, phenols,
steroids, terpenes, courmarins, flavonoids, and glycosides. Quantitative phytochemistry of
the phenolics, flavonoids, alkaloids, and saponins revealed 0.82, 0.04, 1.91, and 2.02%
composition respectively.Sequenial extraction of the methanol extract of V. album leaves
from A. albidawith n-hexane, ethyl acetate, and n-butanol showed thatn-butanolfraction had
the highest yield of 45.26% and was themost active fraction against Trypanosoma brucei
brucei (IC50 = 0.84 mg/mL). Bioassay- guided fractionation of n–butanol fraction and
subsequentpurification of the resulting bioactive compound led to the isolation of [2-(4-
hydroxyphenyl) ethyl]-2,6-dioxabicyclo [3.3.1] nonan-3-one (HDN-one)with in vitro antitrypanosomal
activity against T. b. brucei (IC50 = 0.26 mg/ mL). The compound did not
show toxicity in mice at a dose level of 2000 mg/kg bw. There was a significant decrease in
parasitemia of the group treated with the compound compared to infected untreated group.
The compound had no inhibitory effect on the activity of trypanosome alternative oxidase
(TAO) and trypanosome glycerol kinase (TGK). In conclusion, the results of this study
revealed that HDN-one isolated from V. album leavesdid not show signs of toxicity in mice
at a dose level of 2000 mg/kg body weight and had in vivo anti-trypanosomal activity
against T. b. brucei.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE
STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL
FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF DOCTOR OF
PHILOSPHY IN BIOCHEMISTRY
DEPARTMENT OF BIOCHEMISTRY,
FACULTY OF LIFE SCIENCES,
AHMADU BELLO UNIVERSITY,
ZARIA, NIGERIA