Effects of thermal preparation and in vitro digestion on lignan profiles and antioxidant activity in defatted-sesame meal.

Defatted-sesame meal (DSM), a byproduct of sesame oil, has attracted considerable interest in the food industry because of its strong antioxidant activity. The aim of this study was to measure the content and distribution of lignans in DSM and evaluate their antioxidant activity after thermal processing and in vitro digestion. The results showed that the sesame lignans (SL) content and antioxidant activity were significantly influenced by the temperature and time during thermal preparation, and the maximum antioxidant potency composite index (ACI) was obtained after roasting the samples at 240 °C for 20 min. As sesame seed was processed with longer time and higher temperature, more pinoresinol diglucoside (PD) and sesamol were measured in DSM. According to the correlation matrix under thermal preparation, a significant contribution to the antioxidant potency of DSM was discovered. After in vitro digestion, the release amount of lignans increased by 19.6%, and the values of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and ACI gradually declined after digestion, with a 40% decrease in both the DPPH radical scavenging activity and the ACI from oral to intestinal phase. These results could be used to help improve the bioavailability of SL and obtaining high quality sesame byproducts.

Seed-expressed casein kinase I acts as a positive regulator of the SeFAD2 promoter via phosphorylation of the SebHLH transcription factor.

Microsomal oleic acid desaturase (FAD2) catalyzes the first committed step of the biosynthesis of polyunsaturated fatty acids via extra-plastidial desaturation of oleic acid to linoleic acid. In the regulatory mechanism controlling seed-specific SeFAD2 expression, trans-activation of the seed-specific SeFAD2 promoter is mediated by the SebHLH transcription factor (Kim et al. in Plant Mol Biol 64:453-466, 2007). In this study, a protein interacting with SebHLH was isolated from yeast two-hybrid analysis. The protein shares approximately 80% sequence identity with other putative casein kinases and was named SeCKI (Sesame Casein Kinase I). SeCKI transcripts were predominantly expressed in developing sesame seeds and were induced approximately threefold by exogenous application of ABA. eGFP:SeCKI fusion protein was localized to the nucleus. The SeCKI protein specifically bound to SebHLH. The SeCKI protein was autophosphorylated in a calcium-independent manner and transphosphorylated the SebHLH protein. Both the SebHLH and the SeCKI genes or both the SebHLH and mutated SemCKI (K182G) genes, under the control of CaMV 35S promoter, and the GUS reporter gene driven by SeFAD2 promoter containing E- and G-Box motifs were co-expressed in developing sesame seeds. This co-expression revealed that SeCKI enhanced the SebHLH-mediated transactivation of the SeFAD2 gene promoter via phosphorylation of the SebHLH transcription factor.

Variations of water uptake, lipid consumption, and dynamics during the germination of Sesamum indicum seed: a nuclear magnetic resonance spectroscopic investigation.

Germination in sesame seeds (Sesamum indicum L.) in water and in indole-3-acetic acid (IAA) solution is investigated with magic-angle-spinning (MAS) solid state nuclear magnetic resonance (NMR) spectroscopy, supplemented by liquid state NMR spectroscopy. The spectra show good resolution and can be assigned with sufficient confidence. The characteristic spectral peaks and relaxation rates were monitored during the entire course of germination for better understanding of the biophysical and biochemical mechanisms involved in the triphasic water uptake of the seed. A highly positive correlation is found between water uptake and lipid consumption during germination. No significant variation is observed in the relaxation times for the lipid protons during the first two stages of triphasic water uptake, while evident differences are observed for water proton relaxation rates in all stages. Although the total amount of water uptake is largely not changed as a result of IAA, the addition of IAA in seed-germination medium has shown some prominent effects on the germination process, e.g, it suppresses lipid consumption and water mobility, and it reduces the longitudinal and transverse relaxation times of lipid protons and causes a more scattered range for these parameters.