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 L−1 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

2‑Oxo-Driven N₂ Elimination Induced Decarbonylative Cyclization Reaction in Benzotriazoles to 6‑Aminophenanthridines

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 “CO–CH­(N₁N₂)”. This reaction presents a new mode of N₂ 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

(η⁵‑Cp*)Rh(III)/Ir(III) Complexes with Bis(chalcogenoethers) (E, E′ Ligands: E = S/Se; E′ = S/Se): Synthesis, Structure, and Applications in Catalytic Oppenauer-Type Oxidation and Transfer Hydrogenation

The air- and moisture-insensitive half-sandwich complexes [(η⁵-Cp*)­Rh­(<b>L</b>)­Cl]­[PF₆] (<b>1</b>–<b>3</b>) and [(η⁵-Cp*)­Ir­(<b>L</b>)­Cl]­[PF₆] (<b>4</b>–<b>6</b>) have been prepared by reacting <b>L </b>=<b> L1</b>–<b>L3</b> (1,2-bis­(phenylthio)­ethane (<b>L1</b>), 1-(phenylseleno)-2-(phenylthio)­ethane (<b>L2</b>) and 1,2-bis­(phenylseleno)­ethane (<b>L3</b>)) with [(η⁵-Cp*)­RhCl­(μ-Cl)]₂ and [(η⁵-Cp*)­IrCl­(μ-Cl)]₂, respectively, at room temperature followed by treatment with NH₄PF₆. Their HR-MS and ¹H, ¹³C­{¹H}, and ⁷⁷Se­{¹H} NMR spectra have authenticated them. The single-crystal structures of <b>1</b>–<b>6</b> have been established by X-ray crystallography. Complexes <b>1</b>–<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 × 10² and 9.8 × 10³, respectively) and were therefore investigated in detail. <b>3</b> is the first example of a Rh­(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-bis­(phenylthiomethyl)­benzene­(<b>L1</b>) and 1,2-bis­(phenylselenomethyl)­benzene­(<b>L2</b>) with [(η⁵-Cp*)­MCl­(μ-Cl)]₂ (M = Rh or Ir) at room temperature, followed by treatment with NH₄PF₆ have resulted in air and moisture insensitive half-sandwich complexes of composition [(η⁵-Cp*)­M­(<b>L</b>)­Cl]­[PF₆] (Rh, <b>1</b>–<b>2</b>; Ir, <b>3</b>–<b>4</b>; <b>L</b> = <b>L1</b> or <b>L2</b>). Their HR-MS, ¹H, ¹³C­{¹H}, and ⁷⁷Se­{¹H} NMR spectra were found to be characteristic. The single crystal structures of <b>1</b>–<b>4</b> have been established by X-ray crystallography. The complexes <b>1</b>–<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>–<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)­benzoic acid (<b>L</b>) with [(η⁵-Cp*/η⁶-benzene)­MCl­(μ-Cl)]₂, (benzene, M = Ru; Cp*, M = Rh, Ir) at room temperature followed by treatment with NH₄PF₆ result in a new class of water-soluble half-sandwich complexes [(η⁵Cp*/η⁶-benzene)­M­(<b>L</b>)­Cl]­[PF₆] (<b>1</b>–<b>3</b>, respectively, for M = Ru, Rh, Ir). Their characteristic HR-MS and ¹H and ¹³C­{¹H} NMR spectra have been found. The single-crystal structures of <b>1</b>–<b>3</b> have been established with X-ray crystallography. The Ru–S, Rh–S, and Ir–S bond lengths are 2.4079(6), 2.3989(10), and 2.3637(14) Å, respectively. Complexes <b>1</b>–<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

Epithelial–mesenchymal 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 (4′-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 α‑Ketothioesters

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