dc.description.abstract |
Several scientific studies reveal that the heartwood of the plant Prosopis juliflora
contains very high levels of the flavan-3-ol compound (2R,3S)-2-(3,4-
dihydroxyphenyl)-3,4-dihydro-2H-chromene-3,7,8-triol commonly referred to as
mesquitol. Mesquitol, exhibits free-radical scavenging properties, antioxidant and α-
glucosidase inhibitory properties. This confirms its potential applicability for the
treatment of radical oxidative induced diseases like cancer and atherosclerosis. The
limit in technology transfer, has made P. juliflora a nuisance to people through its
invasive nature and the adverse effects of the pods and thorns on livestock especially
sheep and goats yet the plant has potent medicinal value. Incidentally, limited research
exists on rapid methods for the extraction and quantification of the compound
mesquitol. This study therefore aimed at investigating the abundance dynamics of
mesquitol and to develop and validate a High Performance Liquid Chromatographic
(HPLC) analytical method for quantification of the said compound. Plant samples of
different ages were collected from Marigat in Baringo county, during the wet and dry
seasons of June and December respectively. Soxhlet and maceration methods of
extraction were evaluated for optimality in flavonoids extraction based on their
respective percentage yields after which column chromatography was used to isolate
mesquitol. Thin layer chromatography (TLC) assisted in pooling together of fractions
with similar R f values while melting point apparatus and Fourier Transform Infrared
Spectroscopy were utilized to confirm the isolated flavanol mesquitol. A HPLC-UV
analytical method was developed and validated illustrating high accuracy and precision
for the quantification of the mesquitol content in different P. juliflora samples. The
highest percentage yield during extraction was obtained by soxhlet method with the
solvent methanol (10.22 ± 2.03 %) for samples collected during the wet season. Total
flavonoids however were highest in the acetonic crude extracts (21.7 ±1.1 mg/g
equivalent) hence guiding the selection of the extracts for the chromatographic isolation
of mesquitol. The purified compound was confirmed to be mesquitol by the
characteristic peaks of the flavanols structures which include the O-H broad band
absorption at 3350cm -1 , the aromatic C=C skeletal vibrations at 1625 cm -1 , 1520 cm -
1
and 1480 cm -1 which are typical of flavonoids. The melting temperature range was
found to be between 82-85 O C as previously reported for mesquitol. On quantification,
mesquitol was found to be more abundant during the wet seasons for plants of above 4
years age category reaching 642.893 μg/mL. On the other hand, the lowest amount of
mesquitol was obtained in the dry season as 181.245 μg/mL. This variations in seasonal
abundance, could be attributed to chemo-seasonal dynamics that have been witnessed
to affect biosynthesis and deposition of phyto-compounds in plants like temperature,
availability of water, humidity etc. The developed and validated HPLC method,
illustrated satisfactory quantification of mesquitol at 3-5 % of the crude extract hence
illustrating the potential for related applications in agro-food and pharmaceutical
industry analysis. Given the age and seasons of harvest are significant it is
recommended that evaluation of P. juliflora samples of higher age brackets, 12, 16 and
20 years be carried out to establish mesquitol abundance trends to inform exploitation
of this valuable natural resource. |
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