Phytochemical Reinvestigation Of The Roots Of Eurycoma Longifolia And Development Of A LC-MS Method For Qualitative And Quantitative Analyses Of Their Major Constituents
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Date
2010-07
Authors
Teh, Chin Hoe
Journal Title
Journal ISSN
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Publisher
Universiti Sains Malaysia
Abstract
The 30 % methanol fraction eluted from resin chromatography of methanol extract of
the roots of Eurycoma longifolia Jack showed good antimalarial activity
(Wemsdorfer et al., 2009). Sequential partition of this fraction, followed by
chromatographic separations and recrystallization afforded ten chemical constituents.
Of these, one was a novel C19 longilactone-type quassinoid, named 2,3-dehydro-4ahydroxylongilactone
(117), possessing an unsubstitituted vinyl function and a C-4
methyl group of P---configuration in ring A. Eurycomanone (3) and 13,21-
dihydroeurycomanone (11), the two known quassinoids, were crystallized as novel
crystal structures with a space group of orthorhombic P212121 and monoclinic P21,
respectively. Meanwhile, the two known non-quassinoids, scopolin (118) and 2,3-
dihydroxy-1-(4'-hydroxy-3'-methoxyphenyl)propan-1-one (119) were isolated from
this plant for the first time. All structures were characterized by spectroscopic
analysis (lD and 2D NMR experiments, HRMS, UV, IR and optical rotation) and by
comparison with known spectroscopic data.
Extensive mass spectrometry optimization was performed in order to achieve the
maximum sensitivity for the target analyte. Comparison between electrospray
ionization (ESI) and atmospheric pressure chemical ionization (APCI) was
performed on eurycomanone (3), eurycomanol (4), 13,21-dihydroeurycomanone
(11 ), 13 a(21 )-epoxyeurycomanone (15), eurycomanol-2-0-/i-D-glucopyranoside (9),
and scopolin (118) using automated flow injection analysis (PIA). The effect of
eluent composition (contained methanol or acetonitrile) and acidic modifiers (acetic
acid, formic acid and trifluoroacetic acid) on the ionization efficiency of the
aforementioned standards were also investigated. Subsequently, the effects of
nebulizer pressure, dry gas flow, dry gas temperature and capillary voltage on the
sensitivity of the six compounds in positive ion mode of ESI were measured and
compared. Fragmentation of analytes for subsequent selective Multiple Reaction
Monitoring (MRM) analysis was investigated by varying the capillary exit offset
voltage and fragmentation amplitude in positive mode of ESI.
The detection limits (LODs) were determined in isolation mode (selected ion
monitoring, SIM) for the analytes by LC-ESI-MS positive ion mode in order to
investigate the sensitivity of the assay developed. The LOD values were ranged
between 0.03-0.1 Jlg mL-1 while the intra-day and inter-day precisions, expressed in
relative standard deviations, were less than 5.72 %and 4.82 %, respectively. Based
on the optimal mass spectrometry parameters established, a new analytical method
using HPLC with ESI-MS detection was successfully applied for the simultaneous
determination of the bioactive phytochemical markers of the various batches of
standardised extracts of E. longifolia developed for antimalarial treatment. From the
samples analyzed, eurycomanone (3), eurycomanol ( 4) and eurycomanol-2-0-.B-Dglycopyranoside
(9) were the main quassinoids in the bioactive extracts, whereas
13,21-dihydroeurycomanone (11) and 13a(21)-epoxyeurycomanone (15) existed in
the comparable amount, were present in much lower quantity.
Description
Keywords
The roots of Eurycoma longifolia Jack showed , good antimalarial activity.