24 research outputs found
True-to-typeness and phytomedicinal potential in somatic embryo-derived plants of Crinum malabaricum (Amaryllidaceae): A medicinally important source of pharmaceutical biomolecules
International audienceCrinum malabaricum, Lekhak & S.R. Yadav (Amaryllidaceae) is a critically endangered bulbous plant endemic to India. Establishing an efficient plant regeneration protocol is necessary for its conservation and large-scale propagation. In the present study, regeneration was achieved through somatic embryogenesis from callus produced on MS media supplemented with various different concentrations of 2,4-D alone and in combination with N6-benzyl-adenine (BA). Different advanced stages of embryo development (globular, torpedo and cotyledonary) and maturation were obtained on MS medium, with combinations of picloram and thidiazuron (TDZ). A high rate of somatic embryos (55.89 ± 0.60) was obtained after eight weeks. SEM examinations showed the occurrence of cell clusters (embryogenic) which converted to somatic embryos. Well-developed cotyledon embryos were successfully germinated on PGRs free full and half strength MS medium, however, 94.03% of somatic embryos germinated on half-strength MS medium supplemented with 1.0 mg Lâ1 gibberellic acid. The true-to-type genetic conformity of regenerated plants was examined by SCoT, ISSR and RAPD primers based molecular analysis. The amplification bands produced by SCoT, ISSR and RAPD primers applied were monomorphic across all the regenerated plants. This confirmed their genetic homogeneity compared to the mother plant and also demonstrated the reliability of our somatic embryogenesis system for C. malabaricum. A rapid method for phytochemical analysis based on LC-ESI/MS exhibited better separation and analysis of galanthamine and lycorine from methanolic extracts of in vitro raised plants derived from somatic embryogenesis. The protocol developed should be helpful in reintroduction, restoration and ex situ conservation of this valuable plant in the natural condition as well as in the pharmaceutical sectors
2âOxo-Driven N<sub>2</sub> Elimination Induced Decarbonylative Cyclization Reaction in Benzotriazoles to 6âAminophenanthridines
An
efficient functional group induced strategy for the synthesis
of 6-aminophenanthridines (6AP) has been developed as a result of
an in situ generated novel system âCOâCHÂ(N<sub>1</sub>N<sub>2</sub>)â. This reaction presents a new mode of N<sub>2</sub> extrusion in benzotriazoles that later result in decarbonylative
cyclization to 6AP. This method offers an easier protocol for the
synthesis of 6AP from readily available inexpensive substrates
(η<sup>5</sup>âCp*)Rh(III)/Ir(III) Complexes with Bis(chalcogenoethers) (E, EâČ Ligands: E = S/Se; EâČ = S/Se): Synthesis, Structure, and Applications in Catalytic Oppenauer-Type Oxidation and Transfer Hydrogenation
The air- and moisture-insensitive
half-sandwich complexes [(η<sup>5</sup>-Cp*)ÂRhÂ(<b>L</b>)ÂCl]Â[PF<sub>6</sub>] (<b>1</b>â<b>3</b>) and [(η<sup>5</sup>-Cp*)ÂIrÂ(<b>L</b>)ÂCl]Â[PF<sub>6</sub>] (<b>4</b>â<b>6</b>) have
been prepared by reacting <b>L </b>=<b> L1</b>â<b>L3</b> (1,2-bisÂ(phenylthio)Âethane (<b>L1</b>), 1-(phenylseleno)-2-(phenylthio)Âethane
(<b>L2</b>) and 1,2-bisÂ(phenylseleno)Âethane (<b>L3</b>)) with [(η<sup>5</sup>-Cp*)ÂRhClÂ(ÎŒ-Cl)]<sub>2</sub> and
[(η<sup>5</sup>-Cp*)ÂIrClÂ(ÎŒ-Cl)]<sub>2</sub>, respectively,
at room temperature followed by treatment with NH<sub>4</sub>PF<sub>6</sub>. Their HR-MS and <sup>1</sup>H, <sup>13</sup>CÂ{<sup>1</sup>H}, and <sup>77</sup>SeÂ{<sup>1</sup>H} NMR spectra have authenticated
them. The single-crystal structures of <b>1</b>â<b>6</b> have been established by X-ray crystallography. Complexes <b>1</b>â<b>6</b> have been explored for catalytic Oppenauer-type
oxidation of alcohols and transfer hydrogenation of ketones with 2-propanol. <b>3</b> and <b>6</b> were the most efficient in the two catalytic
reactions (TON values up to 9.9 Ă 10<sup>2</sup> and 9.8 Ă
10<sup>3</sup>, respectively) and were therefore investigated in detail. <b>3</b> is the first example of a RhÂ(III) species explored for Oppenauer-type
oxidation. The catalysis appears to be homogeneous. In transfer hydrogenation
it appears that one of the catalytic species is without a Cp* ring.
DFT calculations indicate higher reactivity for Rh complexes in comparison
to Ir complexes. This order has also been found for the two catalytic
reactions experimentally. The calculated bond lengths/angles by DFT
are generally consistent with the experimental values
Half-Sandwich Rhodium/Iridium(III) Complexes Designed with Cp* and 1,2-Bis(phenylchalcogenomethyl)benzene as Catalysts for Transfer Hydrogenation in Glycerol
The
reactions of 1,2-bisÂ(phenylthiomethyl)ÂbenzeneÂ(<b>L1</b>) and
1,2-bisÂ(phenylselenomethyl)ÂbenzeneÂ(<b>L2</b>) with [(η<sup>5</sup>-Cp*)ÂMClÂ(ÎŒ-Cl)]<sub>2</sub> (M = Rh or Ir) at room temperature,
followed by treatment with NH<sub>4</sub>PF<sub>6</sub> have resulted
in air and moisture insensitive half-sandwich complexes of composition
[(η<sup>5</sup>-Cp*)ÂMÂ(<b>L</b>)ÂCl]Â[PF<sub>6</sub>] (Rh, <b>1</b>â<b>2</b>; Ir, <b>3</b>â<b>4</b>; <b>L</b> = <b>L1</b> or <b>L2</b>). Their HR-MS, <sup>1</sup>H, <sup>13</sup>CÂ{<sup>1</sup>H}, and <sup>77</sup>SeÂ{<sup>1</sup>H} NMR spectra were found to be characteristic. The single
crystal structures of <b>1</b>â<b>4</b> have been
established by X-ray crystallography. The complexes <b>1</b>â<b>4</b> have been found efficient for catalytic transfer
hydrogenation (TH) of aldehydes and ketones in glycerol, which acts
as a solvent and hydrogen source. Complexes <b>1</b>â<b>2</b> are the first examples of Rh species explored for TH in
glycerol. The catalysis appears to be homogeneous. The complexes of
the (Se, Se) ligand are marginally efficient than the corresponding
complexes of the (S, S) ligand. The reactivity of Rh complexes in
comparison to those of Ir also appears to be somewhat more. The results
of DFT calculations appear to be generally consistent with experimental
catalytic efficiencies and bond lengths/angles
Transfer Hydrogenation (pH Independent) of Ketones and Aldehydes in Water with Glycerol: Ru, Rh, and Ir Catalysts with a COOH Group near the Metal on a (Phenylthio)methyl-2-pyridine Scaffold
The
reactions of 2-(pyridine-2-ylmethylsulfanyl)Âbenzoic acid (<b>L</b>) with [(η<sup>5</sup>-Cp*/η<sup>6</sup>-benzene)ÂMClÂ(ÎŒ-Cl)]<sub>2</sub>, (benzene, M = Ru; Cp*, M = Rh, Ir) at room temperature followed
by treatment with NH<sub>4</sub>PF<sub>6</sub> result in a new class
of water-soluble half-sandwich complexes [(η<sup>5</sup>Cp*/η<sup>6</sup>-benzene)ÂMÂ(<b>L</b>)ÂCl]Â[PF<sub>6</sub>] (<b>1</b>â<b>3</b>, respectively, for M = Ru, Rh, Ir). Their
characteristic HR-MS and <sup>1</sup>H and <sup>13</sup>CÂ{<sup>1</sup>H} NMR spectra have been found. The single-crystal structures of <b>1</b>â<b>3</b> have been established with X-ray crystallography.
The RuâS, RhâS, and IrâS bond lengths are 2.4079(6),
2.3989(10), and 2.3637(14) Ă
, respectively. Complexes <b>1</b>â<b>3</b> have been found to be efficient for catalytic
transfer hydrogenation (TH) of carbonyl compounds in water with glycerol
as a hydrogen donor. Glycerol has been explored for TH in water for
the first time. The efficiency in water of other hydrogen sources,
viz. HCOOH, citric acid, ascorbic acid, and 2-propanol, is less and/or
is pH dependent. Catalysis with glycerol as a hydrogen source is pH
independent and appears to be homogeneous. Higher reactivity for the
Rh complex in comparison to the Ru and Ir species has been observed.
DFT calculations are generally consistent with the experimental values
of bond lengths and angles and catalytic reactivity order
Natural podophyllotoxin analog 4DPG attenuates EMT and colorectal cancer progression via activation of checkpoint kinase 2
Epithelialâmesenchymal transition (EMT) is critical for the metastatic dissemination of cancer cells and contributes to drug resistance. In this study, we observed that epithelial colorectal cancer (CRC) cells transiently exposed to 5-fluorouracil (5-FU) (a chemotherapeutic drug for CRC) as well as 5-FU-resistant cells (5-FU-R) develop EMT characters as evidenced by activation of Vimentin and augmented invasive properties. On the other hand, 4DPG (4âČ-demethyl-deoxypodophyllotoxin glucoside), a natural podophyllotoxin analog attenuates EMT and invadopodia formation abilities of HCT-116/5-FU-R and SW-620/5-FU-R cells. Treatment with 4DPG restrains Vimentin phosphorylation (Ser38) in 5-FU-R cells, along with downregulation of mesenchymal markers Twist1 and MMP-2 while augmenting the expression of epithelial markers E-cadherin and TIMP-1. Moreover, 4DPG boosts the tumor-suppressor protein, checkpoint kinase 2 (Chk2) via phosphorylation at Thr68 in a dose-dependent manner in 5-FU-R cells. Mechanistically, SiRNA-mediated silencing of Chk2, as well as treatment with Chk2-specific small-molecule inhibitor (PV1019), divulges that 4DPG represses Vimentin activation in a Chk2-dependent manner. Furthermore, immunoprecipitation analysis unveiled that 4DPG prevents complex formation between Vimentin and p53 resulting in the rescue of p53 and its nuclear localization in aggressive 5-FU-R cells. In addition, 4DPG confers suitable pharmacokinetic properties and strongly abrogates tumor growth, polyps formation, and lung metastasis in an orthotopic rat colorectal carcinoma model. In conclusion, our findings demonstrate 4DPG as a targeted antitumor/anti-metastatic pharmacological lead compound to circumvent EMT-associated drug resistance and suggest its clinical benefits for the treatment of aggressive cancers
Amino Catalytic Oxidative Thioesterification Approach to 뱉Ketothioesters
An efficient metal-free method for
the synthesis of α-ketothioesters
is described for the first time. This reaction features the ability
of pyrrolidine to fine-tune the reaction between 2-oxoaldehyde and
thiols through iminium to the desired product in moderate to good
yields. As an advantage, no external oxidants or metal catalysts are
required in our method. Reactions performed under modified conditions
lead to an apparent balance in reactivity of secondary amine and thiols
toward 2-oxoaldehydes