Biotransformation of resibufogenin by Actinomucor elegans.

Resibufogenin (RB), a major bioactive bufadienolide, has the potential anticancer activity. In the present work, biotransformation of RB by Actinomucor elegans AS 3.2778 yielded five products, namely 3-oxo-resibufogenin (1), 3-epi-resibufogenin (2), 3-epi-12-oxo-hydroxylresibufogenin (3), 3α-acetoxy-15α-hydroxylbufalin (4), and 3-epi-12α-hydroxylresibufogenin (5), respectively. Among them, metabolites 3 and 4 are previously unreported. The chemical structures of metabolites 1-5 were fully elucidated on the basis of 2D NMR and HR-MS. The highly stereo- and regio-specific isomerization, hydroxylation, and esterification reactions were observed in the biotransformation process of RB by A. elegans. Their cytotoxicities against A549 and H1299 cells were evaluated.

Do tillage systems affect the cadmium threshold in farmland soil for environmental quality standard setting?

Tillage systems may change the cadmium (Cd) threshold of farmland soil. However, there have been few studies on this topic. Therefore, this study aimed to explore the influence of tillage systems on Cd threshold. The study conducted 2-year field experiments under different tillage systems (early rice-fallow, early rice-late rice and early rice-vegetable) at three typical Cd-polluted sites in China. The species sensitivity distribution (SSD) method was used to construct the SSD curves for the calculation of the Cd threshold by analyzing the experimental data. The sensitivity analysis results based on the SSD curves revealed that the sensitivities to Cd in rice varieties under the same tillage system were substantially different but almost the same under different tillage systems. These results can help select rice varieties with low Cd sensitivity for crop safety. Different tillage systems at the same site varied in their influence on Cd threshold values. Cd threshold values under early rice-late rice (e.g., 0.27, 0.28 mg/kg in Xiangtan City) and early rice-vegetable (e.g., 0.26, 0.31 mg/kg in Xiangtan City) tillage systems were roughly lower than that under the early rice-fallow tillage system (e.g., 0.33, 0.35 mg/kg in Xiangtan City). Notably, the influence of tillage systems resulted in Cd threshold values being generally lower than the Cd risk screening values of the current Chinese soil environmental quality standard. Analysis of the influence of different tillage systems on the Cd threshold is beneficial for the optimization of farmland soil environmental quality standards.

Variations in volatile flavour compounds in Crataegi fructus roasting revealed by E-nose and HS-GC-MS.

Introduction: Crataegi fructus (CF) is an edible and medicinal functional food used worldwide that enhances digestion if consumed in the roasted form. The odour of CF, as a measure of processing degree during roasting, significantly changes. However, the changes remain unclear, but are worth exploring. Methods: Herein, the variations in volatile flavour compounds due to CF roasting were investigated using an electronic nose (E-nose) and headspace gas chromatography-mass spectrometry (HS-GC-MS). Results: A total of 54 components were identified by GC-MS. Aldehydes, ketones, esters, and furans showed the most significant changes. The Maillard reaction, Strecker degradation, and fatty acid oxidation and degradation are the main reactions that occur during roasting. The results of grey relational analysis (GRA) showed that 25 volatile compounds were closely related to odour (r > 0.9). Finally, 9 volatile components [relative odour activity value, (ROAV) ≥ 1] were confirmed as key substances causing odour changes. Discussion: This study not only achieves the objectification of odour evaluation during food processing, but also verifies the applicability and similarity of the E-nose and HS-GC-MS.