Analytical methods for screening and determination of conventional drugs adulterated in herbal products
Loading...
Date
2023-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine University of Agriculture
Abstract
Herbal products are popular worldwide. Their popularity is
threatened by untrustworthy manufacturers who add
conventional drugs. The addition of conventional drugs
increases the risk of developing antimicrobial resistance and
herb-drug interactions. To safeguard the users and enhance
the safety of herbal products, analytical methods for
screening and determining conventional drugs adulterated
in herbal products are required. Therefore, this study was
carried out to develop analytical methods and apply them in
screening and determination of antibiotic, antimalarial, pain
killer and erectile dysfunction adulterants in herbal products.
Thin layer chromatography methods for screening twelve
conventional drugs in herbal products were developed and
applied. The analytes were extracted from herbal products
using a solvent mixture of acetonitrile:methanol:acetic
acid:water (4:4:1:1, v/v). The mobile phase consisting of
dichloromethane:ethyl acetate:methanol (75:15:10, v/v)
separated well trimethoprim, sildenafil, paracetamol and
sulfamethoxazole. Pyrimethamine, metronidazole and
sulfadoxine were well separated by dichloromethane:ethyl
acetate:methanol (77.5:12.5:10, v/v). In addition, acetyl
salicylic acid, ibuprofen, diclofenac, quinine and
lumefantrine
were
well
separated
by
ethyl
acetate:methanol:30%
ammonia
(75:22.5:2.5,
v/v).
Chromatographic separations were highly reproducible and
more than 10 samples were analysed in one run. The
developed methods were used to screen 229 herbal
products. Consequently, 24.0% of the samples contained
one adulterant while 21.4% contained at least two
adulterants.
A high performance liquid chromatography–tandem mass
spectrometry method was developed and used for screening
and determining six conventional antibiotics (amoxicillin,
ampicillin, metronidazole, trimethoprim, sulfamethoxazole, and ciprofloxacin) in herbal products. The developed method
had linear (r2 ≥ 0.996) calibration curves over the range of
0.005–2.5 μg mL–1 for all compounds except metronidazole,
whose range was 0.005–1 μg mL–1. The limit of detection
ranged from 0.012 to 0.046 μg mL–1 while the limit of
quantification ranged from 0.066 to 0.153 μg mL–1.
Accuracy, expressed as recovery of spiked herbal products
ranged from 45% to 114%. The precision expressed as
relative standard deviation at two concentration levels
ranged from 1.6% to 15.9%. The matrix effect, expressed as
matrix factor ranged from 0.79 to 0.92. The developed
method was used to analyse 78 herbal products purchased
from Njombe, Morogoro, Manyara, Arusha, Mwanza and Dar
es Salaam in Tanzania. Metronidazole was detected in eight
samples with the highest concentration of 1.38 μg g–1.
Another high performance liquid chromatography–tandem
mass spectrometry method was developed and used to
screen and determine eleven conventional antimalarials
(chloroquine,
quinine,
sulfadoxine,
pyrimethamine,
mefloquine, lumefantrine, amodiaquine, artemisinin,
dihydroartemisinin, artesunate and artemether) in herbal
products. The developed method had linear (r2 ≥ 0.991)
calibration curves over the range of 0.001–0.3 μg mL–1 for
all compounds. The limit of detection ranged from 0.002 to
0.02 g mL–1 while the limit of quantification ranged from
0.006 to 0.08 g mL–1. Accuracy, expressed as recovery of
spiked herbal products ranged from 52% to 128%. The
precision, expressed as percent relative standard deviation
at two concentration levels, ranged from 1.0% to 13.8%. The
matrix effect, expressed as the matrix factor ranged from
0.77 to 0.97. The developed method was used to analyse 50
herbal product samples from Njombe, Morogoro, Manyara,
Arusha, Mwanza and Dar es Salaam in Tanzania. Ten of the
herbal products were found to contain amodiaquine,
sulfadoxine, pyrimethamine, mefloquine, dihydroartemisinin,
artemether and lumefantrine. The developed thin layer chromatography and high
performance
liquid
chromatography–tandem
mass
spectrometry methods are considered valuable tools for a
better understanding of the adulteration of herbal products
by addition of conventional drugs. The thin layer
chromatography methods can be used for preliminary
screening of herbal products prior to confirmation by other techniques such as high performance liquid chromatography–tandem mass spectrometry. On the other
hand, confirmation and quantification of the selected
antibiotic and antimalarial adulterants in herbal products can
be achieved using the developed high performance liquid
chromatography–tandem mass spectrometry methods.
Description
Thesis
Keywords
Analytical methods screening, Determination conventional drugs, Adulterated, Herbal products, Herb-drug interactions