Short-term feeding of flaxseed or its lignan has minor influence on in vivo hepatic antioxidant status in young rats

Specialty seeds: Nutrients, bioactives, bioavailability, and health benefits: A comprehensive review

Seeds play important roles in human nutrition and health since ancient time. The term "specialty" has recently been applied to seeds to describe high-value and/or uncommon food products. Since then, numerous studies have been conducted to identify various classes of bioactive compounds, including polyphenols in specialty seeds. This review discusses nutrients, fat-soluble bioactives, polyphenols/bioactives, antioxidant activity, bioavailability, health benefits, and safety/toxicology of commonly consumed eight specialty seeds, namely, black cumin, chia, hemp, flax, perilla, pumpkin, quinoa, and sesame. Scientific results from the existing literature published over the last decade have been compiled and discussed. These specialty seeds, having numerous fat-soluble bioactives and polyphenols, together with their corresponding antioxidant activities, have increasingly been consumed. Hence, these specialty seeds can be considered as a valuable source of dietary supplements and functional foods due to their health-promoting bioactive components, polyphenols, and corresponding antioxidant activities. The phytochemicals from these specialty seeds demonstrate bioavailability in humans with promising health benefits. Additional long-term and well-design human intervention trials are required to ascertain the health-promoting properties of these specialty seeds.

Lignan transformation by gut bacteria lowers tumor burden in a gnotobiotic rat model of breast cancer

High dietary lignan exposure is implicated in a reduced breast cancer risk in women. The bacterial transformation of plant lignans to enterolignans is thought to be essential for this effect. To provide evidence for this assumption, gnotobiotic rats were colonized with the lignan-converting bacteria Clostridium saccharogumia, Eggerthella lenta, Blautia producta and Lactonifactor longoviformis (LCC rats). Germ-free rats were used as the control. All animals were fed a lignan-rich flaxseed diet and breast cancer was induced with 7,12-dimethylbenz(a)anthracene. The lignan secoisolariciresinol diglucoside was converted into the enterolignans enterodiol and enterolactone in the LCC but not in the germ-free rats. This transformation did not influence cancer incidence at the end of the 13 weeks experimental period but significantly decreased tumor numbers per tumor-bearing rat, tumor size, tumor cell proliferation and increased tumor cell apoptosis in LCC rats. No differences between LCC and control rats were observed in the expression of the genes encoding the estrogen receptors (ERs) α, ERβ and G-coupled protein 30. The same was true for IGF-1 and EGFR involved in tumor growth. The activity of selected enzymes involved in the degradation of oxidants in plasma and liver was significantly increased in the LCC rats. However, plasma and liver concentrations of reduced glutathione and malondialdehyde, considered as oxidative stress markers, did not differ between the groups. In conclusion, our results show that the bacterial conversion of plant lignans to enterolignans beneficially influences their anticancer effects.

Fatty acids and lignans in unground whole flaxseed and sesame seed are bioavailable but have minimal antioxidant and lipid-lowering effects in postmenopausal women

Fatty acids and lignans in ground flaxseed and sesame seed are absorbed, metabolized, and exert some health benefits in vivo. However, it is unclear if they are absorbed, metabolized, and exert health benefits when consumed as unground whole seed; therefore, it was investigated in this study. In a randomized crossover study, 16 postmenopausal women supplemented their diets with food bars containing either 25 g unground flaxseed, sesame seed, or their combination (12.5 g each) (flaxseed+sesame seed bar, FSB) for 4 wk each, separated by 4 wk washout periods. Total serum n-3 fatty acids increased with flaxseed (p<0.05) and FSB (p=0.064) while serum n-6 fatty acids increased with sesame seed (p<0.05). Urinary lignans increased similarly with all treatments (p<0.05). Plasma lipids and several antioxidant markers were unaffected by all treatments, except serum gamma-tocopherol (GT), which increased with both sesame seed (p<0.0001) and FSB (p<0.01). In conclusion, fatty acids and lignans from unground seed in food bars are absorbed and metabolized; however, except for serum GT, the 25 g unground seed is inadequate to induce changes in plasma lipids and several biomarkers of oxidative stress.

A linhaça (Linum usitatissimum) como fonte de ácido α-linolênico na formação da bainha de mielina

A linhaça (Linum usitatissimum) é uma semente oleaginosa que tem sido estudada por seus efeitos benéficos à saúde. É considerada um alimento funcional, pelo fato de ser uma fonte natural de fitoquímicos, e por conter o ácido graxo α-linolênico (C18:3 n-3), que pode ser metabolicamente convertido nos ácidos docosaexahenóico (C22:6 n-3) e eicosapentaenóico (C20:5 n-3), sendo o primeiro essencial para o desenvolvimento do sistema nervoso central. Durante o crescimento do cérebro, há uma grande incorporação do ácido docosaexahenóico, que tem papel importante na formação de suas membranas celulares. Diante disto, esta comunicação visa a abordar os prováveis mecanismos pelos quais o ácido docosaexahenóico, proveniente do ácido α-linolênico presente abundantemente na semente de linhaça, interfere na formação da bainha de mielina, assim como relatar a técnica mais adequada para visualização desta bainha.

Engineering Flax with the GT Family 1 Solanum sogarandinum Glycosyltransferase SsGT1 Confers Increased Resistance to Fusarium Infection

The aim of this study was to engineer a flax with increased resistance to pathogens. The approach was based on the recent analysis of the Solanum sogarandinum -derived glycosyltransferase (UGT) protein, designated SsGT1 (previously called 5UGT). On the basis of enzyme studies, the recombinant SsGT1 is a 7-O-glycosyltransferase, the natural substrates of which include both anthocyanidins and flavonols such as kaempferol and quercetin. Because flavonoids act as antioxidants and glycosylation increases the stability of flavonoids, it has been suggested that the accumulation of a higher quantity of flavonoid glycosides in transgenic plants might improve their resistance to pathogen infection. Flax overproducing SsGT1 showed higher resistance to Fusarium infection than wild-type plants, and this was correlated with a significant increase in the flavonoid glycoside content in the transgenic plants. Overproduction of glycosyltransferase in transgenic flax also resulted in proanthocyanin, lignan, phenolic acid, and unsaturated fatty acid accumulation in the seeds. The last is meaningful from a biotechnological point of view and might suggest the involvement of polyphenol glycosides in the protection of unsaturated fatty acids against oxidation and thus improve oil storage. It is thus suggested that introduction of SsGT1 is sufficient for engineering altered pathogen resistance in flax.

Composition and properties of flaxseed phenolic oligomers

An extract from flaxseed containing oligomeric structures of the phenolic glucosides secoisolariciresinol diglucoside (SDG), p-coumaric acid glucoside and ferulic acid glucoside was fractionated into three oligomeric fractions (F50, F60 and F70) by reversed phase liquid chromatography and further subfractionated by Sepharose CL-6B. The F50 fraction, which had the highest proportion of hydroxycinnamic acid glucosides, was also fractionated on Sephadex LH-20 according to hydrophobicity and size. The different separations resulted in complex profiles of UV-absorbing molecules. HPLC analyses indicated that reversed-phase chromatography separated the oligomers according to composition of the phenolic glucosides, while the subfractionation revealed that other structural features of the oligomers were also important. Using the DPPH radical, SDG and oligomeric fractions showed similar hydrogen-donating abilities comparable to ferulic acid but higher than α-tocopherol, which suggests that SDG was the only active antioxidant.

Antioxidant activities of the flaxseed lignan secoisolariciresinol diglucoside, its aglycone secoisolariciresinol and the mammalian lignans enterodiol and enterolactone in vitro

The flaxseed lignan secoisolariciresinol diglucoside (SDG) and mammalian lignans enterodiol (ED) and enterolactone (EL) were previously shown to be effective antioxidants against DNA damage and lipid peroxidation. Others reported inhibition of activated cell chemiluminescence by supra-physiological concentrations of secoisolariciresinol (SECO), ED and EL. Thus, we evaluated the antioxidant efficacy of potential physiological concentrations of SDG, SECO, ED and EL against 1,1-diphenyl-2-picrylhydrazyl (DPPH()), and 2,2'-azo-bis(2-amidinopropane) dihydrochloride (AAPH)-initiated peroxyl radical plasmid DNA damage and phosphatidylcholine liposome lipid peroxidation. SDG and SECO were effective (p<0.01) antioxidants against DPPH() at 25-200muM; whereas, ED and EL were inactive. Efficacy of lignans and controls against AAPH peroxyl radical-induced DNA damage was: SDG>SECO=17alpha-estradiol>ED=EL>genistein>daidzein. Lignan efficacy against AAPH-induced liposome lipid peroxidation was: SDG>SECO=ED=EL. Plant lignan antioxidant activity was attributed to the 3-methoxy-4-hydroxyl substituents of SDG and SECO, versus the meta mono-phenol structures of ED and EL. Benzylic hydrogen abstraction and potential resonance stabilization of phenoxyl radicals in an aqueous environment likely contributed to the antioxidant activity of the mammalian lignans. These represent likely extra- and intracellular antioxidant activities of flax-derived lignans at concentrations potentially achievable in vivo.

Flaxseed and its components reduce metastasis after surgical excision of solid human breast tumor in nude mice

This study determined the effect of 10% flaxseed (FS) and its components, secoisolariciresinol diglycoside (SDG) and flaxseed oil (FO) alone or in combination (SDG+FO), on the metastasis and recurrence of human breast tumor after excision in nude mice. Mice were injected orthotopically with human breast cancer cells (MDA-MB-435) and fed basal diet (BD). When the tumors reached an average size of 110 mm(2) (0.9 g), surgical excisions were performed, and the mice were assigned to one of five diet groups for 7 weeks. The total incidence of metastasis was significantly lower in the FS, SDG, and SDG+FO groups. Reduced lung and lymph node metastases were observed in the FS and SDG+FO groups. In the FS and FO groups, a greater reduction in lung and total metastases was found when excised tumors were <or=0.9 versus >0.9 g. There was no significant difference in tumor recurrence among groups. In conclusion, FS and its components inhibited tumor metastasis but not tumor recurrence after surgical excision of the primary tumor.

Dietary flaxseed alters tumor biological markers in postmenopausal breast cancer

PURPOSE

Flaxseed, the richest source of mammalian lignan precursors, has previously been shown to reduce the growth of tumors in rats. This study examined, in a randomized double-blind placebo-controlled clinical trial, the effects of dietary flaxseed on tumor biological markers and urinary lignan excretion in postmenopausal patients with newly diagnosed breast cancer.

EXPERIMENTAL DESIGN

Patients were randomized to daily intake of either a 25 g flaxseed-containing muffin (n = 19) or a control (placebo) muffin (n = 13). At the time of diagnosis and again at definitive surgery, tumor tissue was analyzed for the rate of tumor cell proliferation (Ki-67 labeling index, primary end point), apoptosis, c-erbB2 expression, and estrogen and progesterone receptor levels. Twenty-four-hour urine samples were analyzed for lignans, and 3-day diet records were evaluated for macronutrient and caloric intake. Mean treatment times were 39 and 32 days in the placebo and flaxseed groups, respectively.

RESULTS

Reductions in Ki-67 labeling index (34.2%; P = 0.001) and in c-erbB2 expression (71.0%; P = 0.003) and an increase in apoptosis (30.7%; P = 0.007) were observed in the flaxseed, but not in the placebo group. No significant differences in caloric and macronutrient intake were seen between groups and between pre- and posttreatment periods. A significant increase in mean urinary lignan excretion was observed in the flaxseed group (1,300%; P < 0.01) compared with placebo controls. The total intake of flaxseed was correlated with changes in c-erbB2 score (r = -0.373; P = 0.036) and apoptotic index (r = 0.495; P < 0.004).

CONCLUSION

Dietary flaxseed has the potential to reduce tumor growth in patients with breast cancer.