Integrated microbiology and metabolomic analysis reveal the improvement of rice straw silage quality by inoculation of Lactobacillus brevis.

BACKGROUND: Ensiling technology holds promise for preserving and providing high-quality forage. However, the preservation of rice straw poses challenges due to its high lignocellulosic content and low water-soluble carbohydrate levels. Developing highly effective lactic acid bacteria (LAB) for rice straw silage remains a priority. RESULTS: This study evaluated the impact of three LAB strains, Lactobacillus brevis R33 (Lac33), L. buchneri R17 (Lac17), and Leuconostoc pseudomesenteroides (Leu), on the fermentation quality of rice straw silage. Rice straw silage inoculated with Lac33 alone or in combination with other strains exhibited significantly lower neutral detergent fiber (NDF) (66.5% vs. 72.3%) and acid detergent fiber (ADF) (42.1% vs. 47%) contents, along with higher lactic acid (19.4 g/kg vs. not detected) and propionic acid (2.09 g/kg vs. 1.54 g/kg) contents compared to control silage. Bacterial community analysis revealed Lactobacillus dominance (> 80%) and suppression of unwanted Enterobacter and Clostridium. Metabolomic analysis highlighted increased carbohydrates and essential amino acids, indicating improved nutrient values in Lac33-inoculated rice straw silage and a potential explanation for Lac33 dominance. CONCLUSIONS: This research identified a highly efficient LAB candidate for rice straw silage, advancing our comprehension of fermentation from integrated microbiology and metabolomic perspectives.

Separation of furostanol saponins by supercritical fluid chromatography.

Supercritical fluid chromatography (SFC) has good separation efficiency and is suitable for separating weakly polar compounds. Furostanol saponins, as an important kind of steroidal saponins, generally have two sugar chains, which are polar and hydrophilic. The hydroxyl group at the C-22 position of furostanol saponins is active and easily reacts with lower alcohols under appropriate conditions. The separation of hydrophilic furostanol saponins was tested by SFC in this study. The effects of chromatographic conditions on the separation of the mixed furostanol saponins and their hydroxyl derivatives at the C-22 position were studied. The conditions for SFC, which included different column polarity, modifier, additive, and column temperature, were tested. After optimization, the mixed 10 similar structures of furostanol saponins were separated in 22min on the Diol column at a temperature of 40°C. The mobile phase was CO2 (mobile phase A) and methanol (containing 0.2% NH3∙H2O and 3% H2O) (mobile phase B). The backpressure was maintained isobarically at 11.03MPa. SFC was found to be effective in separating the furostanol saponins that shared the same aglycone but varied in sugar chains. SFC was sensitive to the number and type of sugars. The resolution of furostanol saponin isomers was not ideal. The extract of Dioscorea zingiberensis C. H. Wright was profiled by SFC-quadrupole time-of-flight mass spectrometry. The main saponins of the extract were well separated. Therefore, SFC could be used for separating hydrophilic furostanol saponins and analyzing traditional Chinese medicines that mainly contained steroidal saponins.

Simultaneous quantification of 11 active constituents in Shexiang Baoxin Pill by ultraperformance convergence chromatography combined with tandem mass spectrometry.

On account of the complexity of chemical constituents of Shexiang Baoxin Pill (SBP), a famous traditional Chinese medicine (TCM) formula, a novel and effective UPC2-MS/MS method was developed to simultaneously determine the content of 11 active compounds of SBP with outstanding separation ability. Eleven components in SBP, including 2 ginsenosides, 2 bile acids, 3 bufadienolides and 4 volatiles were detected by electrospray ionization tandem mass spectrometry in positive and negative ion modes with multiple reaction monitor (MRM). The analysis was performed at 30°C using an Acquity UPC2 Diol (3.0×50mm, 1.7µm) column with linear gradient elution (eluent A, CO2; eluent B, methanol containing 20mM ammonium acetate), back pressure of 2000 psi, flow rate of 1.2mL/min and the injection volume of 1.0µL. The method was extensively validated regarding the linearity (r≥0.9974), precision (≤3.11%), recovery (93.34-104.50%), repeatability (≤2.00%) and stability (≤4.20%). Using this method, 11 active compounds of SBP with different polarity were simultaneously quantified in one chromatography analysis within 8min. Statistical analysis of the effects of 11 compounds on the quality of SBP revealed that the content of cinnamaldehyde varied widely in different batches. This work presents an exemplary study for quality control of complex samples, especially for TCMs.

Comparison of ultra-high performance supercritical fluid chromatography and ultra-high performance liquid chromatography for the separation of spirostanol saponins.

Spirostanol saponins are important active components of some herb medicines, and their isolation and purification are crucial for the research and development of traditional Chinese medicines. We aimed to compare the separation of spirostanol saponins by ultra-high performance supercritical fluid chromatography (UHPSFC) and ultra-high performance liquid chromatography (UHPLC). Four groups of spirostanol saponins were separated respectively by UHPSFC and UHPLC. After optimization, UHPSFC was performed with a HSS C18 SB column or a Diol column and with methanol as the co-solvent. A BEH C18 column and mobile phase containing water (with 0.1% formic acid) and acetonitrile were used in UHPLC. We found that UHPSFC could be performed automatically and quickly. It is effective in separating the spirostanol saponins which share the same aglycone and vary in sugar chains, and is very sensitive to the number and the position of hydroxyl groups in aglycones. However, the resolution of spirostanol saponins with different aglycones and the same sugar moiety by UHPSFC was not ideal and could be resolved by UHPLC instead. UHPLC is good at differentiating the variation in aglycones, and is influenced by double bonds in aglycones. Therefore, UHPLC and UHPSFC are complementary in separating spirostanol saponins. Considering the naturally produced spirostanol saponins in herb medicines are different both in aglycones and in sugar chains, a better separation can be achieved by combination of UHPLC and UHPSFC. UHPSFC is a powerful technique for improving the resolution when UHPLC cannot resolve a mixture of spirostanol saponins and vice versa.

[Determination of pinoresinol diglucoside in Qing' e Pills by ultra performance liquid chromatography].

A new ultra performance liquid chromatographic (UPLC) method was established for the determination of pinoresinol diglucoside (PDG) in Qing' e Pills. After extracted by the Soxhlet's method, the methanol extracts of the samples were passed through a Waters Oasis HLB SPE column to achieve good chromatographic performance. The separation was performed on a Waters Acquity C18 BEH column (100 mm x 1.0 mm, 1.7 microm) with acetonitrile-water (the pH adjusted to 4.0 with phosphoric acid) (9: 91, v/v) as the mobile phase at a flow rate of 0.1 mL/min. The detection wavelength was set at 227 nm, the column temperature was 25 degrees C and the injection volume was 0.5 microL. Under the optimized conditions, there was good linear relationship between the mass concentration and the peak area of PDG in the range of 1.40 - 506.00 mg/L with the correlation coefficient of 1. The average recoveries of PDG at three levels ranged from 100.10% to 102.37%. The method is accurate, sensitive, highly reproducible and suitable for the quality control of Qing' e Pills.

Hydrolysis of flavanone glycosides and degradation of the corresponding aglycones from dried immature Citrus fruit by human fecal flora in vitro.

The hydrolysis of the flavanone glycosides contained in dried immature Citrus fruit, originating from Citrus aurantium L (Family Rutaceae), and degradation of their aglycones in human fecal flora have been analyzed. High-performance liquid chromatography was used to determine the flavanone glycosides and their corresponding aglycones in human fecal flora. The separation of compounds was performed with an ODS column by isocratic and stepwise gradient elution with 0.5 % (v/v) acetic acid-acetonitrile. As a result, the hydrolysis rate of hesperidin and narirutin (flavanone rutinoside) was faster than that of naringin and neohesperidin (flavanone neohesperioside). When the half-life time of each flavanone glycoside was carefully calculated (under the mixed conditions with the human fecal flora), hydrolysis of the flavanone rutinoside turned out to be approximately two times faster than of flavanone neohesperioside. The observed degradation rates of both aglycones was found not to be different. Therefore, it seems that the hydrolysis rate of flavanone glycosides in dried immature citrus fruit with human fecal flora is closely related to the steric hindrance of the sugar. This finding might be effectively used for further pharmacokinetics research on the flavanone glycosides of dried immature Citrus fruit.