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The inhibition mechanism of two homoisoflavonoids from Ophiopogon japonicus including methylophiopogonanone A (MO-A) and methylophiopogonanone B (MO-B) on tyrosinase (Tyr) was studied by multiple spectroscopic techniques and molecular docking. The results showed that the two homoisoflavonoids both inhibited Tyr activity via a reversible mixed-inhibition, with a half inhibitory concentration (IC50) of (10.87 ± 0.25) × 10−5 and (18.76 ± 0.14) × 10−5 mol L−1, respectively. The fluorescence quenching and secondary structure change of Tyr caused by MO-A and B are mainly driven by hydrophobic interaction and hydrogen bonding. Molecular docking analysis indicated that phenylmalandioxin in MO-A and methoxy in MO-B could coordinate with a Cu ion in the active center of Tyr, and interacted with amino acid Glu322 to form hydrogen bonding, occupying the catalytic center to block the entry of the substrate and consequently inhibit Tyr activity. This study may provide new perspectives on the inhibition mechanism of MO-A and MO-B on Tyr and serve a scientific basis for screening effective Tyr inhibitors.

The inhibition mechanism of two homoisoflavonoids from

Dihydromyricetin (DMY) is the main flavonoid present in vine tea and is also known to possess various beneficial health effects. Extractions of DMY from vine tea were investigated by ultrasonic-assisted extraction (UAE) with β-Cyclodextrin (β-CD) and ionic liquid (IL), which were the two green extraction methods attracting more attentions in recent years. Single factor and response surface methodology (RSM) were used in order to optimize the extraction conditions for obtaining maximum amount of DMY in the two approaches. The results of HPLC analysis showed that the addition of β-CD or 1-hexyl-3-methylimidazolium bromide ([HMim] Br) to the water solution had excellent effects on the extraction of DMY. In β-CD-UAE, the optimum conditions were 3.6% β-CD, ultrasonic time 8 min, liquid–solid ratio of 33 (mL/g), and ultrasonic power 360 W. Molecular docking results indicated that the ‘host-guest’ effect between β-CD and the molecule of DMY in water solution, which utilized molecular recognition and interactions through non-covalent bonding and hydrogen bonding is the main driver of the binding. And for IL-UAE, the optimal conditions were 1.25 mol/L [HMim] Br, ultrasonic time 5.5 min, liquid–solid ratio of 45 (mL/g), and ultrasonic power 240 W. Under above suitable conditions, the extraction yield of DMY can reach to about 40%; moreover, β-CD-UAE and IL-UAE can be easily applied for experimental or industrial scale in food or functional food use.

Methylophiopogonanone B (MO-B), which belongs to a group of homoisoflavonoids, present in Ophiopogon japonicus, has been identified as an active component with antioxidative and anti-tumor properties. The present study investigated whether MO-B may exert protective effects on human umbilical vein endothelial cells (HUVECs) against H2O2-induced injury in vitro, and whether the MO-B effects may be modulated by the NADPH pathway. HUVECs were treated with MO-B in the presence or absence of H2O2. Malondialdehyde (MDA), reactive oxygen species (ROS) levels, and superoxide dismutase (SOD) activity were analyzed to evaluate cell injury and the antioxidative potential of MO-B. The results revealed that MO-B inhibited the production of MDA and ROS, but enhanced SOD activity. Furthermore, MO-B could alleviate H2O2-induced apoptosis in HUVECs, which is consistent with the expression of apoptosis-associated genes and proteins in cells, including Bax/Bcl-2 and caspase-3. To explore the potential mechanism, the present study investigated the effects of MO-B on NADPH-related signaling via the analysis of neutrophil cytochrome b light chain (p22phox) expression, which is the membrane-associated subunit of NADPH oxidase. MO-B could improve the survival of endothelial cells and therefore may be a potential drug in the treatment of cardiovascular diseases.

Ionic liquids (ILs), known as environmentally benign &ldquo, green&rdquo, solvents, were developed as an optimal solvent for the green extraction and separation field. In this paper, an ionic liquid-based ultrasonic-assisted extraction (IL-UAE) of flavonoids (FVs) from bamboo leaves of Phyllostachys heterocycla was developed for the first time. First, 1-butyl-3-methylimidazolium bromide ([Bmim] Br), with the best extraction efficiency, was selected from fifteen ionic liquids with diverse structure, like carbon chains or anions. Then, the influencing parameters of ionic liquid (IL) concentration, liquid-solid ratio, ultrasonic time, and ultrasonic power, were investigated by single factor tests, and further optimized using response surface methodology (RSM). In the optimization experiment, the best conditions were 1.5 mol/L [BMIM]Br aqueous solution, liquid-solid ratio 41 mL/g, ultrasonic time 90 min, and ultrasonic power 300 W. Furthermore, the microstructures of bamboo leaves and the recovery of FVs and [BMIM]Br were also studied. Therefore, this simple, green and effective IL-UAE method has potentiality for the extraction of FVs from bamboo leaves for the large-scale operations.

The biomass–density relationship (whereby the biomass of individual plants decreases as plant density increases) has generally been explained by competition for resources. Arbuscular mycorrhizal fungi (AMF) are able to affect plant interactions by mediating resource utilization, but whether this AMF-mediated interaction will change the biomass–density relationship is unclear. We conducted an experiment to test the hypothesis that AMF will shift the biomass–density relationship by affecting intraspecific competition. Four population densities (10, 100, 1,000, or 10,000 seedlings per square meter) of Medicago sativa L. were planted in field plots. Water application (1,435 or 327.7 mm/year) simulated precipitation in wet areas (sufficient water) and arid areas (insufficient water). The fungicide benomyl was applied to suppress AMF in some plots (“low-AMF” treatment) and not in others (“high-AMF” treatment). The effect of the AMF treatment on the biomass–density relationship depended on water conditions. High AMF enhanced the decrease of individual biomass with increasing density (the biomass–density line had a steeper slope) when water was sufficient but not when water was insufficient. AMF treatment did not affect plant survival rate or population size but did affect absolute competition intensity (ACI). When water was sufficient, ACI was significantly higher in the high-AMF treatment than in the low-AMF treatment, but ACI was unaffected by AMF treatment when water was insufficient. Our results suggest that AMF status did not impact survival rate and population size but did shift the biomass–density relationship via effects on intraspecific competition. This effect of AMF on the biomass–density relationship depended on the availability of water.