Acetylcholinesterase inhibition and Cytotoxic activity of extracts and a novel compound isolated from flowers of the wild everlasting (Helichrysum Argyrosphaerum DC)
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Date
2024
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University of Namibia
Abstract
Helichrysum argyrosphaerum is a poisonous plant responsible for livestock losses in
southern Africa. Helichrysum species primarily affect the central nervous system when
ingested by livestock. However, previous attempts to identify the toxins produced by
these plants resulted in only tentative identification of some chemical constituents.
This study aimed to isolate and characterize compounds from the flowers of H.
argyrosphaerum and to determine the in vitro acetylcholinesterase inhibitory activity
and cytotoxicity of the methanol (MeOH) and dichloromethane (DCM) flower extracts
and isolated compounds. Several flavonoid glycosides (tentatively identified as
apigenin-O-glycosides) as well as an unknown chlorogenic acid analogue were
isolated from the methanol extract of H. argyrosphaerum flowers using semi-
preparative high-performance liquid chromatography (HPLC). The chemical
structures of three isolated compounds were elucidated as apigenin, chamaemeloside,
and a novel compound, 14-acetyl chamaemeloside, based on their high-resolution
mass spectrometry (HRMS) and nuclear magnetic resonance spectroscopy (NMR)
data. Interestingly, both the MeOH and DCM H. argyrosphaerum flower extracts as
well as 14-acetyl chamaemeloside induced acetylcholinesterase activity. In the
cytotoxicity assay, neither the MeOH and DCM extracts nor 14-acetyl-
chamaemeloside exhibited toxicity against HeLa cells. This research marks the initial
report of acetylcholinesterase activity and cytotoxicity in both H. argyrosphaerum
MeOH and DCM flower extracts, as well as the isolated compound, 14-acetyl-
chamaemeloside, against HeLa cells. Consequently, these findings will contribute to
future toxicological studies and aid in developing preventative agents that can be used
in the treatment of animals poisoned by H. argyrosphaerum
Description
A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science in Industrial Biochemistry
Keywords
Helichrysum argyrosphaerum, Livestock losses, Neurotoxins, Acetylcholinesterase, Chamaemeloside, Namibia, University of Namibia