Sialic acids are substituted neuraminic acid derivatives which are typically found at the outermost end of glycan chains on the membrane in all cell types. The role of erythrocyte membrane sialic acids during aging has been established however the relationship between sialic acid and oxidative stress is not fully understood. The present work was undertaken to analyze the relationship between erythrocyte membrane sialic acid with its plasma level, membrane and plasma lipid hydroperoxide levels and plasma total antioxidant capacity. Results show that sialic acid content decreases significantly (P < 0.001) in RBC membrane (r = −0.901) and increases in plasma (r = 0.860) as a function of age in humans. Lipid peroxidation measured in the form of hydroperoxides increases significantly (P < 0.001) in plasma (r = 0.830) and RBC membranes (r = 0.875) with age in humans. The Trolox Equivalent Total Antioxidant Capacity (TETAC) of plasma was found to be significantly decreased (P < 0.001, r = −0.844). We observe significant correlations between decrease of erythrocyte membrane sialic acid and plasma lipid hydroperoxide and TETAC. Based on the observed correlations, we hypothesize that increase in oxidative stress during aging may influence the sialic acid decomposition from membrane thereby altering the membrane configuration affecting many enzymatic and transporter activities. Considering the importance of plasma sialic acid as a diagnostic parameter, it is important to establish age-dependent reference.

Breast cancer stem cells are well known to resist the traditional methods like chemo and radio therapy. Aldehyde dehydrogenase 1 (ALDHIA1) and glycogen synthase kinase-3 β (GSK-3β) are the two selected proteins for study, due to their overexpression and upregulation in breast cancer cells. Curcumin, the yellow pigment of the spice turmeric, is widely reported as an antioxidant and acts as a synergist along with traditional drugs. Under hypoxic conditions, it gets converted to free radical which causes apoptosis. Three naturally occurring curcuminoids, i.e. curcumin, demethoxycurcumin, and bisdemethoxycurcumin along with five derivatives/analogues of curcumin, viz. 4,4'-di-O-(carboxy-methyl)-curcumin, 4-O-(2-hydroxyethyl)curcumin, 4,4'-di-O-allyl-curcumin, 4,4'-di-O-(acetyl)-curcumin, and 3,3'-bisdemethylcurcumin were synthesized and evaluated for their anti-breast cancer potential by docking simulation and assessment of their antioxidant character, studied via 2, 2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(·+)) radical cation scavenging assay, 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical, and ferric reducing ability potential (FRAP) assay. A co-relation between structure and activity of curcuminoids/its analogues and derivatives has been worked out.

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Curcumin, an active biphenolic molecule present in turmeric (Curcuma longa), has been reported to elicit plethora of health protective effects. The present study was carried out in vitro, in vivo and in silico to investigate the modulatory effects of curcumin on erythrocyte membrane Na+/K+-ATPase activity. In vitro curcumin (10−5 M to 10−8 M) was incubated with human erythrocytes membrane. In vivo curcumin (340 mg/kg b.w. and 170 mg/kg b.w.) was supplemented to wistar rats for 21 days. In silico, catalytic unit α of Na+/K+-ATPase (3b8e.pdb) protein was used as a receptor for the natural ligand ATP to study curcumin-mediated docking simulation using AutoDock4. The in vitro effect of curcumin on the Na+/K+-ATPase activity in human erythrocytes was biphasic. An inhibitory response was observed at 10−5 M (p < 0.001). An activation of the Na+/K+-ATPase activity was observed at 10−7 and 10−8 M (p < 0.001 and p < 0.01). In vivo, curcumin supplementation to rats increased the Na+/K+-ATPase activity at doses 340 mg/kg b.w. (p < 0.001) as well as at 170 mg/kg b.w., (p < 0.01). AutoDock4 docking simulation study showed that both ligands curcumin and ATP actively interacted with amino acids Glu214, Ser215, Glu216, Thr371, Asn377, Arg378, Met379, Arg438, Val440, Ala444, Lys451 and Asp586 at the catalytic cavity of Na+/K+-ATPase. ATP had more H bonding and hydrophobic interaction with active site amino acid residues compared to curcumin. These finding may explain some of the health beneficial properties of curcumin associated with deregulated Na+/K+-ATPase activity or ions homeostasis.

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Plasma membrane redox system (PMRS) is an electron transport chain system ubiquitously present throughout all cell types. It transfers electron from intracellular substrates to extracellular acceptors for regulation of redox status. Curcumin, isolated from Curcuma longa, has modulatory effects on cellular physiology due to its membrane interaction ability and antioxidant potential. The present study investigates the effect of curcumin on PMRS activity of erythrocytes isolated from Wistar rats in vitro and in vivo and validated through an in silico docking simulation study using Molegro Virtual Docker (MVD). Effects of curcumin were also evaluated on level of glutathione (GSH) and the oxidant potential of plasma measured in terms of plasma ferric equivalent oxidative potentials (PFEOP). Results show that curcumin significantly (p < 0.01) downregulated the PMRS activity in a dose-dependent manner. Molecular docking results suggest that curcumin interacts with amino acids at the active site cavity of cytochrome b 5 reductase, a key constituent of PMRS. Curcumin also increased the GSH level in erythrocytes and plasma while simultaneously decreasing the oxidant potential (PFEOP) of plasma. Altered PMRS activity and redox status are associated with the pathophysiology of several health complications including aging and diabetes; hence, the above finding may explain part of the role of curcumin in health beneficial effects.

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