Herbal Mixture of Carthamus tinctorius L. Seed and Taraxacum coreanum Attenuates Amyloid Beta-Induced Cognitive Dysfunction In Vivo

Deposition of amyloid-beta (Aβ) in the aging brain has been often observed and is thought to be a pathological feature of Alzheimer’s disease. The use of natural products for disease prevention and treatment is gaining attention worldwide. Carthamus tinctorius L. seed and Taraxacum coreanum have been used as traditional medicines in Asian countries, where they have been reported to exert anti-inflammatory and anti-oxidative effects. It has been demonstrated that the combination of C. tinctorius L. seed and T. coreanum has an effect on cognitive enhancement, indicating a ratio of 5:5 synergistically enhancing learning and memory abilities in comparison with a single treatment. Here, we aimed to investigate the protective effect of C. tinctorius L. seed and T. coreanum mixture (CT) at different concentrations on cognition in Aβ25-35-infused mice. CT-administered mice showed significant cognitive improvement in the T-maze, novel object recognition, and Morris water maze tests. Moreover, amyloidogenesis-related proteins, such as β-secretase and γ-secretase, were detected and their protein levels decreased after treatment with CT. Our study shows that CT attenuates cognitive dysfunction by improving learning and memory capability and regulating Aβ-related proteins in Aβ25-35-injected mice. These findings suggest that CT might be a candidate for functional food on cognitive improvement.

Optimization of an analytical HPLC-DAD method for detecting hydroxycinnamic acid derivatives from mixtures of Saussurea grandifolia and Taraxacum coreanum

An analytical method was established to identify and quantify hydroxycinnamic acids, such as 1,5-dicaffeoylquinic acid (DCQA) and chicoric acid (CA), in mixtures of Saussurea grandifolia and Taraxacum coreanum (MST) by using reverse-phase high-performance liquid chromatography coupled with diode array detector (HPLC-DAD). Analyses were carried out by using an INNO C18 column with a gradient elution system, and different parameters were used to validate our optimized method. Results demonstrated limits of detection and quantification of 5.46 × 10–3 and 16.54 × 10–3 mg/mL for DCQA and 0.37 × 10–3 and 1.14 × 10–3 mg/mL for CA, respectively. The calibration curves for DCQA and CA showed good linearity over the concentration ranges of 0.025–0.4 and 0.00625–0.1 mg/mL, respectively, and both exhibited r2 = 1.0000. In the accuracy test, high recovery rates were obtained ranging from 101.16–104.18% for DCQA and 97.55–108.49% for CA, while the precision values were ≤ 1.00% for DCQA and ≤ 1.21% for CA. The values obtained from our analyses support the use of this analytical method for the accurate identification and quantification of DCQA and CA from MST. Our methodology could be used further to determine the content of hydroxycinnamic acid derivatives in routine analyses and large-scale extraction processes.

Production of Multiple triterpenes Including Taraxasterol in Transgenic Tobacco Overexpressing Multifunctional Oxidosqualene Cyclase (TcOSC1) of Taraxacum Coreanum

Taraxasterol and ψ-taraxasterol are pentacyclic triterpenoids, they are commonly found in the family Asteraceae. These two compounds are useful candidates for pharmacologically active triterpenes in dandelion. A multifunctional oxidosqualene cyclase (TcOSC1) of Taraxacum coreanum catalyzes the cyclization of 2,3-oxidosqualene into various triterpenes (taraxasterol, ψ-taraxasterol, δ-amyrin, β-amyrin, α-amyrin, and dammarendiol-II). Here, we established the production of taraxasterol, ψ-taraxasterol, δ-amyrin, β-amyrin, and α-amyrin in transgenic tobacco overexpressing TcOSC1 gene of T. coreanum. Transgenic tobacco overexpressing TcOSC1 gene was induced via Agrobacterium-mediated transformation, and four transgenic lines were selected. Introduction and expression of transgenic genes in tobacco was confirmed by genomic PCR, and qRT-PCR, respectively. All the four transgenic lines of tobacco produced obviously the five triterpenes, namely taraxasterol, ψ-taraxasterol, δ-amyrin, β-amyrin, and α-amyrin. Organ-specific triterpene accumulation occurred in transgenic tobacco plants (leaf > stem > root). The amount of taraxasterol was found the highest among the five triterpenes produced in tobacco. The total amount of triterpenes in transgenic line 3 (Tr3) exhibiting the highest amount of triterpenes that was 598 µg g− 1 dry weight. Production of phytosterols (β-sitosterol, campesterol, and stigmasterol) was reduced in transgenic tobacco compared to those of wild-type control. Conclusively, we successfully established the production of taraxasterol and ψ-taraxasterol triterpenes in transgenic tobacco, which can be applied to the cost-effective production for the utilization and as a source of pharmacologically active materials.

Beneficial Effect of Taraxacum coreanum Nakai via the Activation of LKB1-AMPK Signaling Pathway on Obesity

Objective. Liver kinase B (LKB) 1 and AMP-activated protein kinase (AMPK) are master regulators and sensors for energy homeostasis. AMPK is mainly activated via phosphorylation of LKB1 under energy stress. Here, we highlighted the antiobesity effect and underlying mechanism of Taraxacum coreanum Nakai (TCN) in connection with LKB1-AMPK signaling pathway. Methods. Male C57BL/6 mice were fed on a high-fat diet (60% kcal fat; HFD) to induce obesity. Simultaneously, they received 100 or 200 mg/kg TCN orally for 5 weeks. We measured the body weight gain and liver weight along with liver histology. Moreover, the changes of factors related to lipid metabolism and β-oxidation were analyzed in the liver, together with blood parameters. Results. The body weights were decreased in mice of the TCN200 group more than those of the HFD control group. Moreover, TCN supplementation lowered serum triglyceride (TG) and total cholesterol (TC) levels, whereas TCN increased HDL-cholesterol level. Liver pathological damage induced by HFD was alleviated with TCN treatment and accompanied with significant reduction in serum AST and ALT activities. In addition, TCN significantly increased the expression of p-AMPK compared with the HFD control group via the activation of LKB1/AMPK signaling pathway. Lipid synthesis gene like ACC was downregulated and factors related to β-oxidation such as carnitine palmitoyl transferase-1 (CPT-1) and uncoupling protein 2 (UCP-2) were upregulated through peroxisome proliferator-activated receptor (PPAR) α activation. Conclusion. Taken together, these data suggest that TCN treatment regulates lipid metabolism via LKB1-AMPK signaling pathway and promotes β-oxidation by PPARα; hence, TCN may have potential remedy in the prevention and treatment of obesity.

Cloning and Characterization of Oxidosqualene Cyclases Involved in Taraxasterol, Taraxerol and Bauerenol Triterpene Biosynthesis in Taraxacum coreanum

Triterpenes, consisting of six isoprene units, are one of the largest classes of natural compounds in plants. The genus Taraxacum is in the family Asteraceae and is widely distributed in the Northern Hemisphere. Various triterpenes, especially taraxerol and taraxasterol, are present in Taraxacum plants. Triterpene biosynthesis occurs through the action of oxidosqualene cyclase (OSC), which generates various types of triterpenes from 2,3-oxidosqualene after the rearrangement of the triterpene skeleton. However, no functional characterization of the OSC genes involved in triterpene biosynthesis, except for a lupeol synthase in Taraxacum officinale, has been performed. Taraxacum coreanum, or Korean dandelion, grows in Korea and China. Putative OSC genes in T. coreanum plants were isolated by transcriptome analysis, and four of these (TcOSC1, TcOSC2, TcOSC3 and TcOSC4) were functionally characterized by heterologous expression in yeast. Both TcOSC1 and TcOSC2 were closely related to dammarenediol-II synthases. TcOSC3 and TcOSC4 were strongly grouped with β-amyrin synthases. Functional analysis revealed that TcOSC1 produced several triterpenes, including taraxasterol; Ψ-taraxasterol; α-, β- and δ-amyrin; and dammarenediol-II. TcOSC2 catalyzed the production of bauerenol and another unknown triterpene, TcOSC3 catalyzed the production of β-amyrin. TcOSC4 catalyzed the production of taraxerol. Moreover, we identified taraxasterol, ψ-taraxasterol, taraxerol, lupeol, δ-amyrin, α-amyrin, β-amyrin and bauerenol in the roots and leaves of T. coreanum. Our results suggest that TcOSC1, TcOSC2, TcOSC3 and TcOSC4 are key triterpene biosynthetic enzymes in T. coreanum. These enzymes are novel triterpene synthases involved in the production of taraxasterol, bauerenol and taraxerol.