Flavonoids are among the most investigated phytochemicals due to their pharmacological and therapeutic activities. Their ability to chelate with metal ions has resulted in the emergence of a new category of molecules with a broader spectrum of pharmacological activities. However, the biological significance of these flavonoid-metal ion complexes is yet to be completely explored. Moreover, no concerted efforts have been made to elucidate their molecular targets and mechanisms of action. This review attempts to provide a snapshot of the various biological activities reported for flavonoid-metal ion complexes and their potential as therapeutic agents. Understanding the mechanism of action and the influence of structure will provide a strong basis to design novel flavonoid-metal ion complexes of therapeutic significance.

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Mesoporous nanoparticles are special examples of silica nanoparticles. They are well known for their variety of applications in various fields including biomedicine. This has been attributed to their size, tenability and easily modifiable capabilities because of the presence of functional groups, and their biocompatibility. In this review, we specifically focus on different modes of surface modifications using amino propyl and organic chains which facilitate maximum drug loading and sustained release. This review provides complete information about the importance of surface modifications and their biological consequences that will be helpful to understand the use of MCM-41 and SBA 15 as suitable drug delivery systems.

The present study investigates dose-dependent effects of trans-resveratrol on the membrane fluidity using planar lipid bilayer and liposome models. The complex admittance plots obtained for the lipid bilayer show that resveratrol below 60 μM preferentially interacts with the polar headgroups at the membrane-electrolyte interface, leading to enhanced membrane admittance and vice versa at higher concentrations (>60 μM). This was confirmed using solid-state (13)C and (31)P NMR studies and membrane fluidization studies. The localization of resveratrol in the membrane bilayer was found to alter the membrane rigidity, which resulted in a dose-dependent blebbing and lysis of erythrocytes. The protective effect of trans-resveratrol against DPPH also confirms that its localization in the hydrophobic region prevents lipid peroxidation. The cytotoxic effect of resveratrol on a breast cancer cell line also displays a progressive pattern, indicating possible correlation with its membrane rigidifying properties and localization in the lipid bilayer.

The mechanism of membrane interactions of most of the flavonoids in the presence of transition-metal ions is not well-understood. To understand this phenomenon, the present work aims to synthesize a chrysin-copper complex at room temperature and investigate its influence on the electrical characteristics of planar lipid bilayers. The chrysin-copper complex was characterized by various spectroscopic techniques and was found to have a metal/ligand ratio of 1:2 and of cationic nature. Its ability to inhibit 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radicals was not significant at alkaline pH because of the involvement of the 5-hydroxy group in coordination with the copper ion compared to its parent flavonoid, chrysin (p < 0.05). The addition of different concentrations (20-100 μM) of chrysin and the chrysin-copper complex to lipid bilayers decreases the resistance, indicating a strong surface interaction and partial insertion into the bilayer near the lipid-water interface. The dose-dependent reduction in resistance as a result of the chrysin-copper complex is more pronounced in comparison to chrysin, implying that the bulkier and charged chrysin-copper complex displays greater ability to distort the lipid bilayer architecture. These conclusions were further confirmed by curcumin-loaded liposome permeabilization studies, where both chrysin and its Cu(II) complex increased the fluidity in a dose-dependent manner. However, the extent of fluidization by the chrysin-copper complex was nearly twice that of chrysin alone (p < 0.05). The implications of these surface interactions of chrysin and its copper complex on cell membranes were studied using a hypotonic hemolysis assay. Our results demonstrate that, at low concentrations (20 μM), the chrysin-copper complex exhibited twice the protection against hypotonic stress-induced membrane disruption when compared to chrysin. However, this stabilizing effect gradually decreased and became comparable to chrysin at higher concentrations. This biphasic behavior of the chrysin-copper complex could further be explored for therapeutic applications.

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The present study evaluated the hypoglycemic effect of brown algae Sargassum longiotom in alloxan-induced diabetic rats. After the treatment with S. longiotom extract, there is a significant reduction (p<0.001) in blood glucose when compared with the diabetic control group. Moreover the ethanolic extract of S. longiotom significantly reduces (p<0.001) the levels of triglycerides, low-density lipoprotein cholesterol and very low-density lipoprotein cholesterol dose dependent manner. Alternatively, it increases the highdensity lipoprotein cholesterol level in the treated groups. The values of SGOT, SGPT and ALP have been significantly reduced (p<0.001) in the treated rats when compared to diabetic control. Thus the present study indicates that the ethanolic extract of seaweed S. longiotom posses very effective hypoglycemic and hypolipidemic effect on the alloxan induced diabetic rats compared to the reference drug glibenclamide. Article Info