X-Ray Crystal Structure of Embelin and Its DFT Scavenging of Superoxide Radical.

Embelin is a phytochemical component of tropical plants that have a long history of being used in ethnic pharmacology in various parts of the world, including Ayurdvedic and Chinese medicinal texts. Many modern studies confirm its promise as a medicinal compound. The X-ray crystal structure determination of embelin shows a remarkably ordered alkyl chain and particularly strong pi-pi interactions for a nonaromatic system. The molecule has a torsion angle of 67° between the ring and the alkyl chain of the molecule and differs markedly from that seen when embelin is embedded in the plasminogen activator inhibitor-1 (PAI-1) binding site (almost planar-with about 10° torsion angle). This suggests that embelin's flexible structural skeleton can be useful in biological environment. Apart from this, its many biological activities likely depend on embelin's hydrophobic nonpolar tail that allows a variety of interactions. Computationally, we evaluated embelin's sequestering ability toward the superoxide radical and see that embelin executes this reaction in a novel manner. Namely, as shown by our DFT calculations, instead of releasing a H atom to the superoxide radical to form the anionic species O2 H- , embelin prefers to accept an electron from the superoxide radical, which then transforms into molecular oxygen, O2 . © 2017 Wiley Periodicals, Inc.

beta-sitosterol among other secondary metabolites of Piper galeatum shows inhibition of TNFalpha-induced cell adhesion molecule expression on human endothelial cells.

A phytochemical investigation of the stems of Piper galeatum yielded one novel amide, 1-(3'-hydroxy-5'-methoxycinnamoyl)-piperidine (5) along with four known compounds, i.e. beta-sitosterol (1), cyclostachine-A (2), piperine (3) and piperolein-B (4). The structures of all the five compounds, isolated for the first time from this plant were unambiguously established on the basis of their detailed spectral analysis. The structure of cyclostachine-A (2) was confirmed by X-ray crystallographic studies and structures of known compounds were confirmed by comparison of their physical and/or chemical data with those reported in the literature, which were in complete agreement. Additionally, the crude extracts as well as the isolated pure compounds were screened for their activity to inhibit TNFalpha (tumour necrosis factor-alpha)- induced expression of cell adhesion molecule ICAM-1 (intercellular adhesion molecule-1) on the surface of human umbilical vein endothelial cells (HUVECs). Among all, beta-sitosterol (1) was found to be the most active compound, which was taken for further studies. beta-sitosterol also significantly inhibited the TNFalpha-induced expression of VCAM-1 and E-selectin, which also play key role in various inflammatory diseases. The functional correlation of cell adhesion molecules inhibition was assessed by cell adhesion assay using human neutrophils. We found that beta-sitosterol significantly blocks the adhesion of neutrophils to endothelial monolayer. To elucidate the molecular mechanism of inhibition of cell adhesion molecules, we investigated the status of nuclear transcription factor-kappaB (NF-kappaB) and were able to establish that beta-sitosterol significantly blocked the TNFalpha-induced activation of NF-kappaB.