11 research outputs found
Countercurrent Separation of Natural Products: An Update
This work assesses the current instrumentation,
method development,
and applications in countercurrent chromatography (CCC) and centrifugal
partition chromatography (CPC), collectively referred to as countercurrent
separation (CCS). The article provides a critical review of the CCS
literature from 2007 since our last review (<i>J. Nat. Prod.</i> <b>2008</b>, <i>71</i>, 1489–1508), with
a special emphasis on the applications of CCS in natural products
research. The current state of CCS is reviewed in regard to three
continuing topics (instrumentation, solvent system development, theory)
and three new topics (optimization of parameters, workflow, bioactivity
applications). The goals of this review are to deliver the necessary
background with references for an up-to-date perspective of CCS, to
point out its potential for the natural product scientist, and thereby
to induce new applications in natural product chemistry, metabolome,
and drug discovery research involving organisms from terrestrial and
marine sources
Analysis and Purification of Bioactive Natural Products: The AnaPurNa Study
Based on a meta-analysis of data mined from almost 2000
publications
on bioactive natural products (NPs) from >80 000 pages of
13
different journals published in 1998–1999, 2004–2005,
and 2009–2010, the aim of this systematic review is to provide
both a survey of the status quo and a perspective for analytical methodology
used for isolation and purity assessment of bioactive NPs. The study
provides numerical measures of the common means of sourcing NPs, the
chromatographic methodology employed for NP purification, and the
role of spectroscopy and purity assessment in NP characterization.
A link is proposed between the observed use of various analytical
methodologies, the challenges posed by the complexity of metabolomes,
and the inescapable residual complexity of purified NPs and their
biological assessment. The data provide inspiration for the development
of innovative methods for NP analysis as a means of advancing the
role of naturally occurring compounds as a viable source of biologically
active agents with relevance for human health and global benefit
Natural Deep Eutectic Solvents: Properties, Applications, and Perspectives
As functional liquid media, <u>n</u>atural <u>d</u>eep <u>e</u>utectic <u>s</u>olvent (NADES) species can dissolve
natural or synthetic chemicals
of low water solubility. Moreover, the special properties of NADES,
such as biodegradability and biocompatibility, suggest that they are
alternative candidates for concepts and applications involving some
organic solvents and ionic liquids. Owing to the growing comprehension
of the eutectic mechanisms and the advancing interest in the natural
eutectic phenomenon, many NADES applications have been developed in
the past several years. However, unlike organic solvents, the basic
structural unit of NADES media primarily depends on the intermolecular
interactions among their components. This makes NADES matrices readily
influenced by various factors, such as water content, temperature,
and component ratio and, thus, extends the metabolomic challenge of
natural products (NPs). To enhance the understanding of the importance
of NADES in biological systems, this review focuses on NADES properties
and applications in NP research. The present thorough chronological
and statistical analysis of existing report adds to the recognition
of the distinctiveness of (NA)DES, involves a discussion of NADES-related
observations in NP research, and reportes applications of these eutectic
mixtures. The work identifies potential areas for future studies of
(NA)DES by evaluating relevant applications, including their use as
extraction and chromatographic media as well as their biomedical relevance.
The chemical diversity of natural metabolites that generate or participate
in NADES formation highlights the growing insight that biosynthetically
primordial metabolites (PRIMs) are as essential to the biological
function and bioactivity of unrefined natural products as the biosynthetically
more highly evolutionary metabolites (HEVOs) that can be isolated
from crude mixtures
Can Invalid Bioactives Undermine Natural Product-Based Drug Discovery?
High-throughput biology has contributed
a wealth of data on chemicals,
including natural products (NPs). Recently, attention was drawn to
certain, predominantly synthetic, compounds that are responsible for
disproportionate percentages of hits but are false actives. Spurious
bioassay interference led to their designation as <u>p</u>an-<u>a</u>ssay <u>in</u>terference
compound<u>s</u> (PAINS). NPs lack comparable scrutiny,
which this study aims to rectify. Systematic mining of 80+ years of
the phytochemistry and biology literature, using the NAPRALERT database,
revealed that only 39 compounds represent the NPs most reported by
occurrence, activity, and distinct activity. Over 50% are not explained
by phenomena known for synthetic libraries, and all had manifold ascribed
bioactivities, designating them as <u>i</u>nvalid <u>m</u>etabolic <u>p</u>anaceas (IMPs). Cumulative
distributions of ∼200,000 NPs uncovered that NP research follows
power-law characteristics typical for behavioral phenomena. Projection
into occurrence–bioactivity–effort space produces the
hyperbolic black hole of NPs, where IMPs populate the high-effort
base
Can Invalid Bioactives Undermine Natural Product-Based Drug Discovery?
High-throughput biology has contributed
a wealth of data on chemicals,
including natural products (NPs). Recently, attention was drawn to
certain, predominantly synthetic, compounds that are responsible for
disproportionate percentages of hits but are false actives. Spurious
bioassay interference led to their designation as <u>p</u>an-<u>a</u>ssay <u>in</u>terference
compound<u>s</u> (PAINS). NPs lack comparable scrutiny,
which this study aims to rectify. Systematic mining of 80+ years of
the phytochemistry and biology literature, using the NAPRALERT database,
revealed that only 39 compounds represent the NPs most reported by
occurrence, activity, and distinct activity. Over 50% are not explained
by phenomena known for synthetic libraries, and all had manifold ascribed
bioactivities, designating them as <u>i</u>nvalid <u>m</u>etabolic <u>p</u>anaceas (IMPs). Cumulative
distributions of ∼200,000 NPs uncovered that NP research follows
power-law characteristics typical for behavioral phenomena. Projection
into occurrence–bioactivity–effort space produces the
hyperbolic black hole of NPs, where IMPs populate the high-effort
base
Quantification of a Botanical Negative Marker without an Identical Standard: Ginkgotoxin in <i>Ginkgo biloba</i>
A new strategy for the analysis of
natural products uses a combination
of quantitative <sup>1</sup>H NMR (qHNMR) and adsorbent-free countercurrent
separation (CS) methodology to establish a quantification method for
ginkgotoxin (4′-<i>O</i>-methylpyridoxine) in <i>Ginkgo biloba</i> preparations. The target analyte was concentrated
in a one-step CS process using the ChMWat +2 solvent system (CHCl<sub>3</sub>–MeOH–H<sub>2</sub>O, 10:5:5) and subsequently
assayed by qHNMR. While commercial <i>G. biloba</i> seeds
contained 59 μg of ginkgotoxin per seed, the compound was below
the limit of detection (9 ppm) in a typical leaf extract. Due to the
enrichment potential and loss-free operation of CS, the combination
of CS and qHNMR is a generally suitable approach for threshold assays
aimed at quantifying target compounds such as botanical negative markers
at the low ppm level. As the proof of principle is demonstrated for
relatively small CS capacities (20 mL, 1:40 loading) and modest NMR
sensitivity (<i>n</i> = 16, 400 MHz, 5 mm RT probe), the
approach can be adapted to quantification at the ppb level. The procedure
enables the quantification of a botanical negative marker in the absence
of identical reference material, which otherwise is a prerequisite
for LC-based assays
Correction to Importance of Purity Evaluation and the Potential of Quantitative <sup>1</sup>H NMR as a Purity Assay
Correction to Importance
of Purity Evaluation and
the Potential of Quantitative <sup>1</sup>H NMR as a Purity Assa
Importance of Purity Evaluation and the Potential of Quantitative <sup>1</sup>H NMR as a Purity Assay
In any biomedical and chemical context,
a truthful description of chemical constitution requires coverage
of both structure and purity. This qualification affects all drug
molecules, regardless of development stage (early discovery to approved
drug) and source (natural product or synthetic). Purity assessment
is particularly critical in discovery programs and whenever
chemistry is linked with biological and/or therapeutic outcome. Compared
with chromatography and elemental analysis, quantitative NMR (qNMR)
uses nearly universal detection and provides a versatile and orthogonal
means of purity evaluation. Absolute qNMR with flexible calibration
captures analytes that frequently escape detection (water, sorbents).
Widely accepted structural NMR workflows require minimal or no adjustments
to become practical <sup>1</sup>H qNMR (qHNMR) procedures with simultaneous
qualitative and (absolute) quantitative capability. This study reviews
underlying concepts, provides a framework for standard qHNMR purity
assays, and shows how adequate accuracy and precision are achieved
for the intended use of the material
Real-Time Volumetric Phase Monitoring: Advancing Chemical Analysis by Countercurrent Separation
Countercurrent
separation (CCS) utilizes the differential partitioning
behavior of analytes between two immiscible liquid phases. We introduce
the first platform (“CherryOne”) capable of real-time
monitoring, metering, and control of the dynamic liquid–liquid
CCS process. Automated phase monitoring and volumetrics are made possible
with an array of sensors, including the new permittivity-based phase
metering apparatus (PMA). Volumetric data for each liquid phase are
converted into a dynamic real-time display of stationary phase retention
(Sf) and eluent partition coefficients (<i>K</i>), which
represent critical parameters of CCS reproducibility. When coupled
with the elution–extrusion operational mode (EECCC), automated
Sf and <i>K</i> determination empowers untargeted and targeted
applications ranging from metabolomic analysis to preparative purifications
Orthogonal Analysis Underscores the Relevance of Primary and Secondary Metabolites in Licorice
Licorice botanicals are produced
from the roots of <i>Glycyrrhiza</i> species (Fabaceae),
encompassing metabolites of both plant and rhizobial
origin. The composition in both primary and secondary metabolites
(1°/2°Ms) reflects the physiologic state of the plant at
harvest. Interestingly, the relative abundance of 1°Ms vs 2°Ms
in licorice extracts remains undetermined. A centrifugal partition
chromatography (CPC) method was developed to purify liquiritin derivatives
that represent major bioactive 2°Ms and to concentrate the polar
1°Ms from the crude extract of <i>Glycyrrhiza uralensis</i>. One objective was to determine the purity of the generated reference
materials by orthogonal UHPLC-UV/LC-MS and qHNMR analyses. The other
objectives were to evaluate the presence of 1°Ms in purified
2°Ms and define their mass balance in a crude botanical extract.
Whereas most impurities could be assigned to well-known 1°Ms, <i>p</i>-hydroxybenzylmalonic acid, a new natural tyrosine analogue,
was also identified. Additionally, in the most polar fraction, sucrose
and proline represented 93% (w/w) of all qHNMR-quantified 1°Ms.
Compared to the 2°Ms, accounting for 11.9% by UHPLC-UV, 1°Ms
quantified by qHNMR defined an additional 74.8% of <i>G. uralensis</i> extract. The combined orthogonal methods enable the mass balance
characterization of licorice extracts and highlight the relevance
of 1°Ms, and accompanying metabolites, for botanical quality
control