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• HPLC-DAD-APCI/MS was set up for analysis of flavonoid aglycones in the RBP. • The method is capable of providing higher sensitivity and repeatability. • Four methods were applied and assessed for extraction of flavonoids from RBP. • The highest extraction efficiency of flavonoids from RBP was achieved by MAE. • MAE is of short extraction time, low solvent consumption and homogeneous conditions.<br>For identification and quantification of flavonoid aglycones in rape bee pollen (RBP) collected from the Qinghai-Tibetan Plateau, a high-performance liquid chromatography (HPLC) separation method with diode array detector (DAD) and atmospheric pressure chemical ionization/mass spectrometric (APCI/MS) detection and four extraction methods (i.e. microwave-assisted extraction, Soxhlet extraction, cold-soaked extraction, and heat reflux extraction) were developed in this study. The identification of flavonoid aglycones was based on retention time and mass spectra by comparison with standards. Results demonstrated that this method showed excellent reproducibility and correlation coefficient, and offered the detection limits of 0.77-15.50 pmol at signal-to-noise ratio of 3. Quercetin and kaempferol were presented in RBP, and microwave-assisted extraction (MAE) was superior to the other three methods in terms of efficiency, convenience and high content of quercetin (1.37 ± 0.059 mg/g) and kaempferol (23.44 ± 0.544 mg/g). Our work indicated that: 1) the proposed HPLC-DAD-APCI/MS was an accurate and precise analysis method to identify and quantify the flavonoid aglycones in RBP; and 2) MAE was efficient to extract flavonoids from RBP with short extraction time, low solvent consumption, and homogeneous extraction conditions.
Fenugreek (Trigonella foenum-graecum L.) is a well-known annual plant that is widely distributed worldwide and has possessed obvious hypoglycemic and hypercholesterolemia characteristics. In our previous study, three polyphenol stilbenes were separated from fenugreek seeds. Here, we investigated the effect of polyphenol stilbenes on adipogenesis and insulin resistance in 3T3-L1 adipocytes. Oil Red O staining and triglyceride assays showed that polyphenol stilbenes differently reduced lipid accumulation by suppressing the expression of adipocyte-specific proteins. In addition, polyphenol stilbenes improved the uptake of 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG) by promoting the phosphorylation of protein kinase B (AKT) and AMP-activated protein kinase (AMPK). In present studies, it was found that polyphenol stilbenes had the ability to scavenge reactive oxygen species (ROS). Results from adenosine triphosphate (ATP) production and mitochondrial membrane potentials suggested that mitochondria play a critical role in insulin resistance and related signaling activation, such as AKT and AMPK. Rhaponticin, one of the stilbenes from fenugreek, had the strongest activity among the three compounds in vitro. Future studies will focus on mitochondrial biogenesis and function.
Aims: <b>Nelumbo nucifera</b> (Gaertn.) leaves are used widely in modulating obesity in traditional Chinese medicine. Our previous work demonstrated that aporphine alkaloids from it increased the glucose consumption in mature 3T3-L1 adipocytes. However, the underlying mechanisms of this increase remain unclear. Here we investigated the modulating effects of pronuciferine and nuciferine on lipogenesis and glucose uptake in insulin resistant 3T3-L1 adipocytes <b>in vitro</b>.<br>Main methods: Insulin resistant 3T3-L1 mature adipocytes were induced with dexamethasone, 3-isobutyl-methylxanthine and insulin. The lipid droplets and the intracellular triglyceride contents in mature adipocytes were detected by Oil red O staining and colorimetry respectively. The glucose uptake was measured with a fluorescent deoxyglucose analog (2-NBDG). The glucose transporter type 4 (GLUT-4) expression was measured by fluorescent-immunohistochemistry and the activation of 5′-AMP-activated protein kinase (AMPK) was detected by its alpha subunit phosphorylation.<br>Key findings: Both nuciferine and pronuciferine treatments significantly decreased the lipid droplets and the intracellular triglyceride contents but increased the glucose uptake in the insulin resistant 3T3-L1 adipocytes. Furthermore, both pronuciferine and nuciferine showed the ability to up-regulate the expression of GLUT4, triggering the phosphorylation of AMPK in mature 3T3-L1 adipocytes, although pronuciferine exhibited a more powerful effect compared to nuciferine.<br>Significance: In summary, all the results demonstrate that pronuciferine and nuciferine ameliorate the glucose and lipid metabolism in insulin-resistant 3T3-L1 adipocytes, which might be due to the activation of the AMPK signaling pathway.
A method of using high-speed counter-current chromatography (HSCCC) for preparative isolation and purification of oligostilbenes from the ethanol extracts of seed kernel of Iris lactea Pall. var. chinensis (Fisch.) Koidz was established in this study. Four oligostilbenes were successfully separated and purified by HSCCC with two sets of two-phase solvent system, n-hexane-ethyl acetate-methanol-water (3:6:4.2:5.5, v/v/v/v) in the head-to-tail elution mode for the first separation to mainly isolate vitisin A (58 mg), ɛ-viniferin (76 mg) and peak II (43 mg) from 300 mg of the crude ethanol extracts, and then light petroleum-ethyl acetate-methanol-water (5:5:3:6, v/v/v/v) in the tail-to-head elution mode for the second separation to isolate vitisin B (52 mg) and vitisin C (11 mg) from 100mg of peak II. The purities of the isolated four oligostilbenes were all over 95.0% as determined by HPLC. Vitisin A, vitisin B and vitisin C, resveratrol tetramers, were isolated from Iris lactea for the first time. The preparation of crude sample was simple and the HSCCC method for the isolation and purification of four oligostilbenes was rapid, efficient and economical.