Synthesis and biological studies of a new ginkgolide C derivative: Evidence that the cardioprotective effect of ginkgolides is unrelated to PAF inhibition

Identification of VDAC1 as a cardioprotective target of Ginkgolide B

Ginkgolide B (GB), a compound derived from Ginkgo biloba, exhibits significant cardioprotective properties, although its precise molecular target has yet to be identified. In this study, we synthesized a biotin-labeled GB probe (GB-biotin) to identify the molecular targets of GB. Our experiments demonstrated that treatment with GB or GB-biotin reduced mitochondrial injury, restored mitochondrial membrane potential, and decreased cell apoptosis in a concentration-dependent manner. Additionally, GB increased mitochondrial oxygen consumption rate, indicating improved mitochondrial bioenergetics. Proteomic analysis revealed that the voltage-dependent anion channel 1 (VDAC1) is a key protein that interacts with GB-biotin. This finding was further confirmed through cellular thermal shift assay (CETSA) and molecular docking, which revealed hydrogen bond formation between GB and VDAC1. Furthermore, overexpression of VDAC1 diminished the protective effects of GB, highlighting the crucial role of VDAC1 in GB-mediated cardioprotection. These findings identify VDAC1 as a therapeutic target for GB in vitro, providing valuable insights into the cardioprotective mechanisms of GB and the development of novel cardioprotective strategies.

Copper(II)-mediated O-arylation of protected serines and threonines

An effective protocol toward the O-arylation of β-hydroxy-α-amino acid substrates serine and threonine has been developed via Chan-Lam cross-coupling. This Cu(II)-catalyzed transformation involves benign open-flask conditions that are well-tolerated with a variety of protected (Boc-, Cbz-, Tr-, and Fmoc-) serine and threonine derivatives and various potassium organotrifluoroborates and boronic acids.

Hemodynamic and metabolic effects of the beta-phosphorylated nitroxide 2-diethoxyphosphoryl-2,5,5-trimethylpyrrolidinoxyl during myocardial ischemia and reperfusion

In vitro, the stable six-membered ring nitroxide 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) is known to protect the ischemic and reperfused myocardium through a mechanism likely to involve the limitation of free radical damage. In vivo, TEMPO's high rate of reduction into diamagnetic nonactive compounds could limit its pharmacological use and its potential as an ESR probe in oxymetry studies. Recently, beta-phosphorylated nitrones and pyrrolidines have been reported to protect against myocardial reperfusion injury better than their nonphosphorylated analogs. Using hemodynamic, metabolic, and enzymatic indices of reperfusion injury, the efficacy of 2-diethoxyphosphoryl-2,5,5-trimethylpyrrolidinoxyl (TMPPO), a five-membered ring beta-phosphorylated nitroxide, has been compared to that of TEMPO when added at a nontoxic concentration (1 mM) in buffer-perfused isolated rat hearts during low-flow ischemia, total ischemia, and reflow. TMPPO, which is five times as hydrophilic and eight times as resistant to reduction in a biological medium as TEMPO, was more effective in reducing postischemic contracture and myocardial enzymatic leakage. Since a diamagnetic analog of TMPPO was far less protective and both nitroxides showed an antilipoperoxidant effect and acted mainly when administered only at reflow, it was proposed that beta-phosphorylated nitroxides such as TMPPO could be interesting alternatives in pharmacological and ESR applications.

Preparation of 7-substituted ginkgolide derivatives: potent platelet activating factor (PAF) receptor antagonists

Ginkgolides are structurally unique constituents of Ginkgo biloba extracts and are known antagonists of the platelet-activating factor (PAF) receptor. Ginkgolide C is 25-fold less potent than ginkgolide B as a PAF receptor antagonist, due to the presence of the 7beta-OH. Recently, we found that 7alpha-fluoro ginkgolide B was equipotent to ginkgolide B underlining the critical importance of the 7-position of ginkgolides for PAF receptor activity. Herein we describe the synthesis of a series of ginkgolide B derivatives with modifications at the 7-position and the pharmacological evaluation of these derivatives as assayed by cloned PAF receptors. In two cases nucleophilic attack on a 7beta-O-triflate ginkgolide B did not lead to the expected products, but gave rise to two unprecedented ginkgolide derivatives, one with a novel rearranged skeleton. Furthermore, standard reduction of 7alpha-azido ginkgolide B did not give the expected primary amine, but instead yielded alkylated amines depending on the solvent employed. Pharmacological testing with cloned PAF receptors showed that ginkgolides with 7alpha-substitutents had increased affinity compared to 7beta-substituents, in particular 7alpha-chloro ginkgolide B, the most potent nonaromatic ginkgolide derivative described to date with a K(i) value of 110 nM.