Available online A B S T R A C TAntioxidants play an important role in food preservation by inhibiting oxidation processes and contributing to health promotion rendered by many dietary supplements, nutraceuticals and functional food ingredients. Antioxidant activity can be monitored by a variety of assays with different mechanisms, including hydrogen atom transfer (HAT), single electron transfer (ET), reducing power, and metal chelation, among others. Understanding the principle mechanisms, advantages and limitations of the measurement assays is important for proper selection of method(s) for valid evaluation of antioxidant potential in desired applications.This contribution provides a general and up-to-date overview of methods available for measuring antioxidant activity and the chemistry behind them.

MEG3 is a maternally expressed imprinted gene suggested to function as a non-coding RNA. Our previous studies suggest that MEG3 has a function of tumor suppression. The tumor suppressor p53 plays a central role in tumor suppression and mediates the functions of many other tumor suppressors. Therefore, we hypothesized that MEG3 functions through activation of p53. We found that transfection of expression constructs for MEG3 and its isoforms results in a significant increase in p53 protein levels and dramatically stimulates p53-dependent transcription from a p53-responsive promoter. Using this as the functional assay, we demonstrated that the open reading frames encoded by MEG3 transcripts are not required for MEG3 function, and the folding of MEG3 RNA is critical to its function, supporting the concept that MEG3 functions as a non-coding RNA. We further found that MEG3 stimulates expression of the growth differentiation factor 15 (GDF15) by enhancing p53 binding to the GDF15 gene promoter. Interestingly, MEG3 does not stimulate p21 CIP1 expression, suggesting that MEG3 can regulate the specificity of p53 transcriptional activation. p53 degradation is mainly mediated by the mouse double minute 2 homolog (MDM2). We found that MDM2 levels were down-regulated in cells transfected with MEG3, suggesting that MDM2 suppression contributes at least in part to p53 accumulation induced by MEG3. Finally, we found that MEG3 is able to inhibit cell proliferation in the absence of p53. These data suggest that MEG3 non-coding RNA may function as a tumor suppressor, whose action is mediated by both p53-dependent and p53-independent pathways.

Lipids are a major component of food and important structural and functional constituents of cells in biological systems. However, this diverse group of substances is prone to oxidation through various pathways. Their oxidative stability depends on a number of intrinsic and extrinsic factors, including the unsaturation of their fatty acids, composition of minor components, environment conditions, delivery techniques and use of antioxidants, among others. Lipid oxidation has detrimental effects on both food quality and human health, and efforts must be made to minimize oxidation and improve oxidative stability of lipid products. Antioxidant strategy has been successfully employed in the food industry for quality preservation of the food products and in the medicinal industry for risk reduction of numerous oxidative stress-mediated diseases. This tutorial review will provide important knowledge about lipid oxidation, including the mechanism and factors involved in oxidation, as well as strategies for improving oxidative stability of lipids.

Meningiomas are common tumors, representing 15% to 25% of all central nervous system tumors. NF2 gene inactivation on chromosome 22 has been shown as an early event in tumorigenesis; however, few factors underlying tumor growth and progression have been identified. The chromosomal abnormalities of 14q32 are often associated with meningioma pathogenesis and progression; therefore, it has been proposed that an as yet unidentified tumor suppressor is present at this locus. Maternally expressed gene 3 (MEG3) is an imprinted gene located at 14q32 which encodes a noncoding RNA with an antiproliferative function. We found that MEG3 mRNA is highly expressed in normal arachnoidal cells. However, MEG3 is not expressed in the majority of human meningiomas or the human meningioma cell lines IOMM-Lee and CH157-MN. There is a strong association between loss of MEG3 expression and tumor grade. Allelic loss at the MEG3 locus is also observed in meningiomas, with increasing prevalence in higher grade tumors. In addition, there is an increase in CpG methylation within the promoter and the imprinting control region of MEG3 gene in meningiomas. Functionally, MEG3 suppresses DNA synthesis in both IOMM-Lee and CH157-MN cells by ∼60% in bromodeoxyuridine incorporation assays. Colony-forming efficiency assays show that MEG3 inhibits colony formation in CH157-MN cells by ∼80%. Furthermore, MEG3 stimulates p53-mediated transactivation in these cell lines. Therefore, these data are consistent with the hypothesis that

Autoxidation in food and biological systems is responsible for a multitude of adverse effects and implications in human health as well as in food stability and preservation. Antioxidants play a major role in preventing or delaying autoxidation and have attracted much attention as food stabilizers, dietary supplements and natural health products. Both synthetic and natural antioxidants are widely used in food products and an ever increasing number of research papers have appeared in the recent literature on the discovery and application of natural antioxidants and their therapeutic use in inhibiting a myriad of diseases. However, some common synthetic antioxidants have also become controversial due to their potential adverse effects on health. This overview provides the latest developments about novel antioxidants, particularly phenolic derivatives, peptides/protein hydrolysates, phospholipids and polysaccharides, and their role in food quality preservation and human health promotion.

Maternally expressed gene 3 (MEG3) is an imprinted gene highly expressed in the human pituitary. However, MEG3 expression is lost in human gonadotroph-derived pituitary adenomas and most human tumor cell lines. Expression of MEG3 in tumor cells results in growth suppression, p53 protein increase, and activation of p53 downstream targets. The MEG3 gene encodes a noncoding RNA of approximately 1700 nucleotides. There are 12 different MEG3 gene transcripts, generated by alternative splicing. They contain the common exons 1-3 and exons 8-10, but each uses one or more exons 4-7 in a different combination in the middle. MEG3 isoform expression patterns are tissue and cell type specific. Functionally, each isoform stimulates p53-mediated transactivation and suppresses tumor cell growth. We analyzed the secondary RNA folding structure of each MEG3 isoform, using the computer program mfold. All MEG3 RNA isoforms contain three distinct secondary folding motifs M1, M2, and M3. Deletion analysis showed that motifs M2 and M3 are important for p53 activation. Furthermore, a hybrid MEG3 RNA, containing a piece of artificially synthesized sequence different from the wild type but folding into a similar secondary structure, retained the functions of both p53 activation and growth suppression. These results support the hypothesis that a proper folding structure of the MEG3 RNA molecule is critical for its biological functions. This study establishes for the first time the structure-function relationship of a large noncoding RNA and provides a first look into the molecular mechanisms of the biological functions of a large noncoding RNA.

The polar paradox is a theory that illustrates the paradoxical behavior of antioxidants in different media and rationalizes the fact that polar antioxidants are more effective in less polar media, such as bulk oils, while nonpolar antioxidants are more effective in relatively more polar media, such as oil-in-water emulsions or liposomes. For 2 decades since it was proposed, the theory has been used to interpret results in antioxidant efficiency studies. However, more recently, new evidence from more comprehensive assessments has emerged that contradicts the polar paradox theory, hence necessitating its re-evaluation. More complex factors in addition to polarity must be taken into account to explain antioxidant efficacy.

Epigallocatechin gallate (EGCG) is the major polyphenol in green tea and known to render many health benefits associated with tea consumption. EGCG was modified structurally to improve its lipophilicity, expand its application in lipophilic media, and enhance its cellular absorption in vivo. Esterification of the water-soluble EGCG with selected long-chain saturated and unsaturated fatty acids was carried out, followed by a purification process. Ester derivatives of EGCG with stearic acid (SA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) were prepared, and their enhanced lipophilicity was confirmed by octanol-water partition coefficient. The chemical structures of the EGCG derivatives, determined by HPLC-MS and ¹H and ¹³C NMR, were EGCG-3',5',3'',5''-O-tetraesters of SA, EPA, and DHA. The lipophilized EGCG derivatives exhibited greater antioxidant activity in scavenging the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical than EGCG itself. The results suggest that EGCG derivatives may be used as potential lipophilic antioxidants in the food, cosmetic, and medicinal industries.