Separation and Purification of Five Flavone Glucosides and One Lignan from Caragana korshinskii Kom. by the Combination of HSCCC and Semi-preparative RPLC

Recent advances in methods of extraction, pre-concentration, purification, identification, and quantification of kaempferol

As a naturally widely-occurring dietary, cosmetic, and therapeutic flavonoid, kaempferol has gained much consideration for its nutritional and pharmaceutical properties in recent years. Although there have been performed a high number of studies associated with different aspects of kaempferol's analytical investigations, the lack of a comprehensive summary of the various methods and other plant sources that have been reported for this compound is being felt, especially for many biological applications. This study, aimed to provide a detailed compilation consisting of sources (plant species) and analytical information that was precisely related to the natural flavonoid (kaempferol). There is a trend in analytical research that supports the application of modern eco-friendly instruments and methods. In conclusion, ultrasound-assisted extraction (UAE) is the most general advanced method used widely today for the extraction of kaempferol. During recent years, there is an increasing tendency towards the identification of kaempferol by different methods.

Identification and Characterization of the Tyrosinase Inhibitory Activity of Caffeine from Camellia Pollen

Tyrosinase inhibitors are important in cosmetic, medical, and food industries due to their regulation of melanin production. A tyrosinase inhibitor was purified from Camellia pollen using high-speed countercurrent chromatography and preparative high-performance liquid chromatography and was identified as caffeine by NMR and mass spectrometry. It showed strong mushroom tyrosinase inhibitory activity with an IC₅₀ of 18.5 ± 2.31 μg/mL in a noncompetitive model. The caffeine did not interact with copper ions in the active center of the enzyme but could quench fluorescence intensity and change the secondary conformation of this tyrosinase. A molecular dynamics simulation showed that caffeine bound this tyrosinase via Lys379, Lys 376, Asp357, Glu356, Thr308, Gln307, Asp312, and Trp358, thus changing the binding sites of l-tyrosine and the loop conformation adjacent to the active center. In vitro cell model analysis revealed that caffeine exhibited significant inhibitory effects on both intracellular tyrosinase activity and melanin production of B16-F10 melanoma cells in a concentration-dependent manner. These comprehensive results suggest that caffeine is a strong tyrosinase inhibitor that has the potential to be developed as skin-whitening agents in the cosmetics and pharmaceutical industries or as antibrowning agents in the food industry.

Phytochemical composition, isolation and hepatoprotective activity of active fraction from Veronica ciliata against acetaminophen-induced acute liver injury via p62-Keap1-Nrf2 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Veronica ciliata Fisch, a traditional Tibetan medicine, used to cure hepatitis and existed in lots of Tibetan medicine prescriptions owing to its hepatoprotective activity.

AIMS OF THIS STUDY

In this study, we are aimed to systematically analysis and isolate the chemical constituents of the ethyl acetate fraction from V. ciliata (EAFVC), and test the hepatoprotective effect and mechanism of EAFVC and its compounds on attenuating the liver injury induced by acetaminophen (APAP) in vivo and vitro.

MATERIALS AND METHODS

UPLC-PDA-ESI-MS method was established for the analysis of the components in EAFVC, which was further separated using multiple chromatographic techniques. The MS, ¹H and ¹³C NMR were applied to elucidate their structures. UPLC-PDA method was applied for the simultaneous quantification of major compounds of EAFVC. Furthermore, the protective effect of the EAFVC was determined using APAP-induced acute hepatotoxicity in mice and BRL-3A cells model, respectively. In addition, the hepatoprotective activity of two main compounds in EAFVC on relieving APAP-induced liver injury was further evaluated. Finally, we have some concerns about the protective mechanism of EAFVC via enzyme-linked immunosorbent assay (ELISA), reactive oxygen species (ROS) detection, quantitative real-time PCR (qPCR), western blot analysis and molecular docking.

RESULTS

Thirteen compounds were successfully identified using UPLC-PDA-ESI-MS for the first time. Meanwhile, other twelve compounds were separated from EAFVC. Eventually, twenty-five compounds were successfully identified from the EAFVC. Among these compounds, fourteen compounds (3, 8, 10, 14-17, 19-25) were separated from V.ciliata for the first time. In addition, UPLC-PDA analysis method was first to establish for simultaneous determination of the main compounds (1, 2, 4, 5, 7, 9, 12). Further assay indicated that the liver injury in mice induced by APAP showed a significant reversal by EAFVC, as evidenced by reducing the activities of liver function enzymes, suppressing the lipid peroxidation as well as increasing the serum total antioxidant capacity (T-AOC) and the activities of antioxidant enzymes. Pathological sections showed that the liver in the high dose has significant improvement in mice. In vitro experiment also showed that EAFVC elevate the viability, inhibiting the activities of liver function enzymes as well as the generation of ROS of BRL-3A cells. In addition, Catalposide and verproside could reverse the low cell viability of BRL-3A cells induced by APAP. The mechanism research in vitro demonstrated that EAFVC could promote the mRNA and protein expression of heme oxygenase-1 (HO-1), NAD(P) H dehydrogenase quinone 1 (NQO-1) and catalytic or modify subunit of glutamate-cysteine ligase (GCLC/GCLCM) via enhancing nuclear factor-E2-related factor 2 (Nrf2) and p62/SQSTM1 (p62) expression in protein level. Molecular docking results demonstrated that catalposide and verproside have strong affinity to the kelch-like ECH-associated protein-1(Keap1) Kelch domain.

CONCLUSION

This research is the first to clarify the substance basis of the hepatoprotective activity of the EAFVC and provide the further scientific data for the traditional use of this Tibetan Medicine. EAFVC is valuable to be further investigated as active preparations for application in liver protection via activating p62- Keap1-Nrf2 pathway.

A new isoflavane-4-ol derivative from Melilotus officinalis (L.) Pall

A new isoflavane derivative, melilofficinaside together with seven other metabolites including coumarin, uridine, methyl-α-d-fructofuranoside, and flavonoid glucosides were isolated from the aerial parts of Melilotus officinalis (L.) Pall.

Hypaphorine, an Indole Alkaloid Isolated from Caragana korshinskii Kom., Inhibites 3T3-L1 Adipocyte Differentiation and Improves Insulin Sensitivity in Vitro

Obesity, a major health problem worldwide, is a complex multifactorial chronic disease that increases the risk for insulin resistance, type 2 diabetes, coronary heart disease, and hypertension. In this study, we assessed methods to isolate hypaphorine, a potent drug candidate for obesity and insulin resistance. Semi-preparative reversed-phase liquid chromatography (semi-preparative RPLC) was established as a method to separate three compounds, adenosine, l-tryptophan, and hypaphorine, from the crude extracts of Caragana korshinskii Kom. Due to its specific chemical structure, the effect of hypaphorine on differentiation and dexamethasone (DXM) induced insulin resistance of 3T3-L1 cells was investigated. The structures of the three compounds were confirmed by UV, ¹ H-NMR, and ¹³ C-NMR analysis and compared with published data. The activity results indicated that hypaphorine prevented the differentiation of 3T3-L1 preadipocytes into adipocytes by down-regulating hormone-stimulated protein expression of peroxisome proliferator activated receptor γ (PPARγ) and CCAAT/enhancer binding protein (C/EBPα), and their downstream targets, sterol regulatory element binding protein 1 c (SREBP1c) and fatty acid synthase (FAS). Hypaphorine also alleviated DXM-induced insulin resistance in differentiated 3T3-L1 adipocytes via increasing the phosphorylation level of Akt2, a key protein in the insulin signaling pathway. Taken together, we suggest that the method can be applied to large-scale extraction and large-quantity preparation of hypaphorine for treatment of obesity and insulin resistance.

HSCCC separation and enantiomeric distribution of key volatile constituents of Piper claussenianum (Miq.) C. DC. (Piperaceae)

High Speed Countercurrent Chromatography (HSCCC) technique was used for the preparative isolation of the major leishmanicidal compounds from the essential oils of Piper claussenianum species in Brazil. The essential oils from inflorescences of P. claussenianum were analyzed by GC-FID and GC-MS. The enantiomeric ratio of the major constituents of the P. claussenianum essential oils were determined using a Rt-DEXsm chiral capillary column by GC-FID analysis. It was found an enantiomeric excess of (+)-(E)-nerolidol in the leaves, and (+)-linalool and (+)-(E)-nerolidol in the inflorescences essential oil. The major volatile terpenes alcohols were isolated in preparative scale from inflorescences: linalool (320.0 mg) and nerolidol (95.0 mg) in high purity level. The HSCCC, a support-free liquid-liquid partition chromatographic technique, proved to be an effective and useful method for fast isolation and purification of hydrophobic and similarly structured bioactive components from essential oils of Piper species.

Chemical Constituents of Smilax china L. Stems and Their Inhibitory Activities against Glycation, Aldose Reductase, α-Glucosidase, and Lipase

The search for natural inhibitors with anti-diabetes properties has gained increasing attention. Among four selected Smilacaceae family plants, Smilax china L. stems (SCS) showed significant in vitro anti-glycation and rat lens aldose reductase inhibitory activities. Bioactivity-guided isolation was performed with SCS and four solvent fractions were obtained, which in turn yielded 10 compounds, including one phenolic acid, three chlorogenic acids, four flavonoids, one stilbene, and one phenylpropanoid glycoside; their structures were elucidated using nuclear magnetic resonance and mass spectrometry. All solvent fractions, isolated compounds, and stem extracts from plants sourced from six different provinces of South Korea were next tested for their inhibitory effects against advanced glycation end products, as well as aldose reductase. α-Glucosidase, and lipase assays were also performed on the fractions and compounds. Since compounds 3, 4, 6, and 8 appeared to be the superior inhibitors among the tested compounds, a comparative study was performed via high-performance liquid chromatography with photodiode array detection using a self-developed analysis method to confirm the relationship between the quantity and bioactivity of the compounds in each extract. The findings of this study demonstrate the potent therapeutic efficacy of SCS and its potential use as a cost-effective natural alternative medicine against type 2 diabetes and its complications.