Electrospray tandem mass spectrometry analysis of methylenedioxy chalcones, flavanones and flavones

Synthesis of chromones, annulated with oxygen-containing heterocycles with two hetero atoms at C(7)-C(8) bond

The present review represented the advanced synthetic strategies for chromones annulated at the C(7)-C(8) bond with five-membered, six-membered, and seven-membered oxygen-containing heterocycles with two heteroatoms, such as 6H-[1,3]dioxolo[4,5-h]chromen-6-one, 2,3-dihydro-7H-[1,4]dioxino[2,3-h]chromen-7-one, 3,4-dihydro-2H,8H-[1,4]dioxepino[2,3-h]chromen-8-one, 2,3-dihydro-1H,7H-chromeno[7,8-b][1,4]oxazin-7-one, 4H,12H-pyrano[2,3-a]phenoxazine-4-one and 9,10-dihydro-4H,8H-chromeno[8,7-e][1,3]oxazin-4-one. The biological activity of naturally occurring and modified synthetic fused hetarenochromones has been also highlighted.

Recent (2000-2015) developments in the analysis of minor unknown natural products based on characteristic fragment information using LC-MS

Liquid chromatography-Mass Spectrometry (LC-MS) has been widely used in natural product analysis. Global detection and identification of nontargeted components are desirable in natural product research, for example, in quality control of Chinese herbal medicine. Nontargeted components analysis continues to expand to exciting life science application domains such as metabonomics. With this background, the present review summarizes recent developments in the analysis of minor unknown natural products using LC-MS and mainly focuses on the determination of the molecular formulae, selection of precursor ions, and characteristic fragmentation patterns of the known compounds. This review consists of three parts. Firstly, the methods used to determine unique molecular formula of unknown compounds such as accurate mass measurements, MSⁿ spectra, or relative isotopic abundance information, are introduced. Secondly, the methods improving signal-to-noise ratio of MS/MS spectra by manual-MS/MS or workflow targeting-only signals were elucidated; pure precursor ions can be selected by changing the precursor ion isolated window. Lastly, characteristic fragmentation patterns such as Retro-Diels-Alder (RDA), McLafferty rearrangements, "internal residue loss," and so on, occurring in the molecular ions of natural products are summarized. Classical application of characteristic fragmentation patterns in identifying unknown compounds in extracts and relevant fragmentation mechanisms are presented (RDA reactions occurring readily in the molecular ions of flavanones or isoflavanones, McLafferty-type fragmentation reactions of some natural products such as epipolythiodioxopiperazines; fragmentation by "internal residue loss" possibly involving ion-neutral complex intermediates). © 2016 Wiley Periodicals, Inc. Mass Spec Rev 37:202-216, 2018.

LC/ESI-MS/MS profiling of Ulmus parvifolia extracts and evaluation of its anti-inflammatory, cytotoxic, and antioxidant activities

In this study, a comparative liquid chromatography/mass spectroscopy (LC/ESI-MS/MS) profiling of different fractions of Ulmus parvifolia leaves and stems was performed. Identification of compounds was based on comparing the mass spectrometric information obtained including m/z values and individual compound fragmentation pattern to tandem mass spectral library search and literature data. Eleven compounds were tentatively identified in the different analyzed fractions. One of the major constituents of this plant was isolated and identified as Icariside E4 [dihydro-dehydro-diconiferyl alcohol-4-O-α-L-rhamnopyranoside] (5). The evaluation of anti-inflammatory activity of the total methanolic extract using nitric oxide inhibition on LPS-stimulated RAW 264.7 cells model strong anti-inflammatory activity with 17.5% inhibition of nitric oxide production versus 10% inhibition for dexamethasone. The cytotoxic activity of the methanolic extract and Icariside E4 was evaluated against four types of human cell lines using MTT assay. Icariside E4 showed cytotoxic effect against Hep-G2, MCF-7, and CACO-2 cell lines compared to a negligible activity for the total extract. The same extract showed a moderate antioxidant activity with SC50=362.5 μg/mL.

Arylidene indanone scaffold: medicinal chemistry and structure–activity relationship view

Arylidene indanone (AI) scaffolds are considered as the rigid cousins of chalcones, incorporating the α,β-unsaturated ketone system of chalcones forming a cyclic 5 membered ring.

A Fundamental Tandem Mass Spectrometry Study of the Collision-Activated Dissociation of Small Deprotonated Molecules Related to Lignin

The collision-activated fragmentation pathways and reaction mechanisms of 34 deprotonated model compounds representative of lignin degradation products were explored experimentally and computationally. The compounds were evaporated and ionized by using negative-ion mode electrospray ionization doped with NaOH to produce abundant deprotonated molecules. The ions were isolated and subjected to collision-activated dissociation (CAD). Their fragment ions were then isolated and also subjected to CAD. This was repeated until no further fragmentation was observed (up to MS⁶ ). This approach enabled the identification of characteristic reaction pathways and delineation of reasonable fragmentation mechanisms for deprotonated molecules containing various functional groups. The varying fragmentation patterns observed for different types of compounds allow for the identification of the functionalities in these compounds. This information was utilized to identify the presence of specific functionalities and their combinations in molecules in an organosolv lignin sample.

LC-UV/MS methods for the analysis of prochelator-boronyl salicylaldehyde isonicotinoyl hydrazone (BSIH) and its active chelator salicylaldehyde isonicotinoyl hydrazone (SIH)

Salicylaldehyde isonicotinoyl hydrazone (SIH) is an intracellular iron chelator with well documented potential to protect against oxidative injury both in vitro and in vivo. However, it suffers from short biological half-life caused by fast hydrolysis of the hydrazone bond. Recently, a concept of boronate prochelators has been introduced as a strategy that might overcome these limitations. This study presents two complementary analytical methods for detecting the prochelator-boronyl salicylaldehyde isonicotinoyl hydrazone-BSIH along with its active metal-binding chelator SIH in different solution matrices and concentration ranges. An LC-UV method for determination of BSIH and SIH in buffer and cell culture medium was validated over concentrations of 7-115 and 4-115 μM, respectively, and applied to BSIH activation experiments in vitro. An LC-MS assay was validated for quantification of BSIH and SIH in plasma over the concentration range of 0.06-23 and 0.24-23 μM, respectively, and applied to stability studies in plasma in vitro as well as analysis of plasma taken after i.v. administration of BSIH to rats. A Zorbax-RP bonus column and mobile phases containing either phosphate buffer with EDTA or ammonium formate and methanol/acetonitrile mixture provided suitable conditions for the LC-UV and LC-MS analysis, respectively. Samples were diluted or precipitated with methanol prior to analysis. These separative analytical techniques establish the first validated protocols to investigate BSIH activation by hydrogen peroxide in multiple matrices, directly compare the stabilities of the prochelator and its chelator in plasma, and provide the first basic pharmacokinetic data of this prochelator. Experiments reveal that BSIH is stable in all media tested and is partially converted to SIH by H2O2. The observed integrity of BSIH in plasma samples from the in vivo study suggests that the concept of prochelation might be a promising strategy for further development of aroylhydrazone cytoprotective agents.

Methylenedioxy flavonoids: assessment of cytotoxic and anti-cancer potential in human leukemia cells

A new series of chalcones, flavanones and flavones with methylenedioxy group at the 3',4' position in chalcone, 7,8 position in flavanones and flavones with mono-, di- and trimethoxy groups in the benzaldehyde ring have been assessed for their effect on proliferation, cytotoxic potential and apoptosis in human leukemia cells. Among the tested compounds, the chalcone series showed the best activity and chalcone 3 (mono methoxy group at the ortho position in A-ring) showed a significant effect on down-regulation of cancer cell proliferation and viability in three different leukemia cell lines (K562, Jurkat, U937). The executioner caspase cleavage analyses indicated that the cytotoxic effect mediated by chalcone 3 is due to induction of apoptotic cell death. Interestingly, the cytotoxic effect was cell type-specific and targeted preferentially cancer cells as peripheral blood mononuclear cells (PBMCs) from healthy donors were less affected by the treatment compared to K562, Jurkat and U937 leukemia cells. Altogether our results indicate a potential drug candidate with interesting differential toxicity obeying Lipinski's rule of five.

Structural analysis of 2-arylidene-1-indanone derivatives by electrospray ionization tandem mass spectrometry

RATIONALE

2-arylidene-4-methoxy (or hydroxy)-7-methyl-1-indanone derivatives inspired from donepezil, the current drug used for the treatment of Alzheimer's disease as inhibitor of acetylcholinesterase (AChE), were studied for the first time by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). Structurally, these arylidene-indanone compounds are considered as cyclic analogues of chalcones.

METHODS

ESI-MS and tandem mass spectra were acquired using a Q-TOF 2 instrument. Fragmentation patterns were analyzed by CID-MS(2-3) spectra acquired in a Q-TOF and in LXQ linear ion trap mass spectrometers using standard isolation and excitation procedures.

RESULTS

All the 2-arylidene indanones have shown a common fragmentation pathway leading to a (2(1), 1')A(+) product ion at m/z 187 and the retro-aldol product ion [(2, 2(1))B(+)] that allow to establish the substitution in the B ring. The effect of electron-donating and -withdrawing substituents on these fragmentation pathways was noticed. The presence of the OCH3, OH, NO2 and Br substituents gave typical fragmentation processes that allowed their unequivocal fingerprinting. The combined loss of the ortho substituent in the B-ring plus hydrogen (H, OCH3, Br and F) is proposed to form a stable cyclic ring product.

CONCLUSIONS

Arylidene indanones with different substituents on the B ring are associated with a specific fragmentation pattern. In addition, differentiation between isomers with substituents in B ring at ortho and para positions were achieved using ESI-MS/MS. These fragmentation pathways can be used to further identify and determine the fate of these molecules in all stages of drug discovery.