Biotechnological approaches to enhance salidroside, rosin and its derivatives production in selected Rhodiola spp. in vitro cultures

Highly efficient biosynthesis of salidroside by a UDP-glucosyltransferase-catalyzed cascade reaction

OBJECTIVE

Salidroside is an important plant-derived aromatic compound with diverse biological properties. The main objective of this study was to synthesize salidroside from tyrosol using UDP-glucosyltransferase (UGT) with in situ regeneration of UDP-glucose (UDPG).

RESULTS

The UDP-glucosyltransferase 85A1 (UGT85A1) from Arabidopsis thaliana, which showed high activity and regioselectivity towards tyrosol, was selected for the production of salidroside. Then, an in vitro cascade reaction for in situ regeneration of UDPG was constructed by coupling UGT85A1 to sucrose synthase from Glycine max (GmSuSy). The optimal UGT85A1-GmSuSy activity ratio of 1:2 was determined to balance the efficiency of salidroside production and UDP-glucose regeneration. Different cascade reaction conditions for salidroside production were also determined. Under the optimized condition, salidroside was produced at a titer of 6.0 g/L with a corresponding molar conversion of 99.6% and a specific productivity of 199.1 mg/L/h in a continuous feeding reactor.

CONCLUSION

This is the highest salidroside titer ever reported so far using biocatalytic approach.

Natural anti-inflammatory products for osteoarthritis: From molecular mechanism to drug delivery systems and clinical trials

Osteoarthritis (OA) is a degenerative joint disease that affects millions globally. The present nonsteroidal anti-inflammatory drug treatments have different side effects, leading researchers to focus on natural anti-inflammatory products (NAIPs). To review the effectiveness and mechanisms of NAIPs in the cellular microenvironment, examining their impact on OA cell phenotype and organelles levels. Additionally, we summarize relevant research on drug delivery systems and clinical randomized controlled trials (RCTs), to promote clinical studies and explore natural product delivery options. English-language articles were searched on PubMed using the search terms "natural products," "OA," and so forth. We categorized search results based on PubChem and excluded "natural products" which are mix of ingredients or compounds without the structure message. Then further review was separately conducted for molecular mechanisms, drug delivery systems, and RCTs later. At present, it cannot be considered that NAIPs can thoroughly prevent or cure OA. Further high-quality studies on the anti-inflammatory mechanism and drug delivery systems of NAIPs are needed, to determine the appropriate drug types and regimens for clinical application, and to explore the combined effects of different NAIPs to prevent and treat OA.

Neuroprotective effect of salidroside on hippocampal neurons in diabetic mice via PI3K/Akt/GSK-3β signaling pathway

BACKGROUND

Diabetic encephalopathy is manifested by cognitive dysfunction. Salidroside, a nature compound isolated from Rhodiola rosea L, has the effects of anti-inflammatory and antioxidant, hypoglycemic and lipid-lowering, improving insulin resistance, inhibiting cell apoptosis, and protecting neurons. However, the mechanism by which salidroside alleviates neuronal degeneration and improves learning and memory impairment in diabetic mice remains unclear.

OBJECTIVE

To investigate the effects and mechanisms of salidroside on hippocampal neurons in streptozotocin-induced diabetic mice.

MATERIALS AND METHODS

C57BL/6 mice were randomly divided into 4 groups to receive either sham (control group (CON)), diabetes mellitus (diabetes group (DM)), diabetes mellitus + salidroside (salidroside group (DM + SAL)), and diabetes mellitus + salidroside + phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 (diabetes mellitus + salidroside + LY294002 group (DM + SAL + LY294002)). After 12 weeks of diabetes onset, the cognitive behaviors were tested using Morris water maze. The number of hippocampal neurons was detected by Nissl staining. The expressions of PI3K, p-PI3K, Akt, p-Akt, GSK-3β, p-GSK-3β, cleaved caspase-3, caspase-3, Bax, Bcl-2, MAP2, and SYN in the hippocampus were detected by Western blot. Moreover, the expression of MAP2 and SYN in the hippocampus was further confirmed by immunofluorescence staining.

RESULTS

Salidroside increased the time of diabetic mice in the platform quadrant and reduced the escape latency of diabetic mice. Salidroside also increased the expression of p-PI3K, p-Akt, p-GSK-3β, MAP2, SYN, Bcl-2, while suppressed the expression of cleaved caspase-3, caspase3, and Bax in the DM + SAL group compared with the DM group (P < 0.05). The Nissl staining showed that the number of hippocampus neurons in the DM + SAL group was increased with the intact, compact, and regular arrangement, compared with the DM groups (P < 0.05). Interestingly, the protective effects of salidroside on diabetic cognitive dysfunction, hippocampal morphological alterations, and protein expressions were abolished by inhibition of PI3K with LY294002.

CONCLUSIONS

Salidroside exerts neuroprotective properties in diabetic cognitive dysfunction partly via activating the PI3K/Akt/GSK-3β signaling pathway.

Hairy Root Cultures as a Source of Phenolic Antioxidants: Simple Phenolics, Phenolic Acids, Phenylethanoids, and Hydroxycinnamates

Plant-derived antioxidants are intrinsic components of human diet and factors implicated in tolerance mechanisms against environmental stresses in both plants and humans. They are being used as food preservatives and additives or ingredients of cosmetics. For nearly forty years, Rhizobium rhizogenes-transformed roots (hairy roots) have been studied in respect to their usability as producers of plant specialized metabolites of different, primarily medical applications. Moreover, the hairy root cultures have proven their value as a tool in crop plant improvement and in plant secondary metabolism investigations. Though cultivated plants remain a major source of plant polyphenolics of economic importance, the decline in biodiversity caused by climate changes and overexploitation of natural resources may increase the interest in hairy roots as a productive and renewable source of biologically active compounds. The present review examines hairy roots as efficient producers of simple phenolics, phenylethanoids, and hydroxycinnamates of plant origin and summarizes efforts to maximize the product yield. Attempts to use Rhizobium rhizogenes-mediated genetic transformation for inducing enhanced production of the plant phenolics/polyphenolics in crop plants are also mentioned.

The Effect of Low Positive Temperatures on the Formation of Secondary Metabolites in Rhodiola quadrifida (Pall.) Fisch. et C.A. Mey. In Vitro Cultures

Global warming is one of the most serious problems leading to changes in the distribution areas of species and biodiversity. Rhodiola quadrifida is a rare plant with adaptogenic properties and grows in the highlands in a narrow temperature range of 2–15 °C. The aim of our work was to study the growth and content of the main metabolites in two in vitro cultures of Rhodiola quadrifida at temperatures of 5, 15 and 25 °C. Hairy roots and calli were cultivated on agar medium for 28 days. The maximum values of the growth index were observed at 25 °C (2.32 and 2.12 for calli and hairy roots, respectively). HPLC-MS showed the absence of tyrosol and rosarin in both cultures, and rosin in the root culture. The content of salidroside changed slightly in calli and roots. Cultivation at 5 °C significantly stimulated the formation of rosin in calli. Only a residual amount of rosavin was noted in the roots, regardless of temperature. The content of rosin was higher in calli at 15 °C with a maximum content at the end of the cultivation cycle 25 µg/g DW. Thus, Rhodiola quadrifida will be able to grow with an increase in temperature by 10 °C but this will be accompanied by a significant reduction in its medicinal value

Salidroside in the Treatment of NAFLD/NASH

Non-alcoholic fatty liver disease (NAFLD) is the commonest reason for chronic liver diseases in the world and is commonly related to the hepatic manifestation of the metabolic syndrome. Non-alcoholic steatohepatitis (NASH) is a deteriorating form of NAFLD, which can eventually develop into fibrosis, cirrhosis, and liver cancer. The reason for NAFLD/NASH development is complicated, such as liver lipid metabolism, oxidative stress, inflammatory response, apoptosis and autophagy, liver fibrosis and gut microbiota. Apart from bariatric surgery and lifestyle changes, officially approved drug therapy for NAFLD/NASH treatment is lacking. Salidroside (SDS) is a phenolic compound extensively distributed in the tubers of Rhodiola plants, which possesses many significant biological activities. This review summarized the related targets regulated by SDS in treating NAFLD/NASH. It is indicated that SDS could improve the status of NAFLD/NASH by ameliorating abnormal lipid metabolism, inhibiting oxidative stress, regulating apoptosis and autophagy, reducing inflammatory response, alleviating fibrosis and regulating gut microbiota. In conclusion, although the multiple bioactivities of SDS have been confirmed, the clinical data are inadequate and need to become the focus of attention in the later study.

De Novo Production of Hydroxytyrosol by Saccharomyces cerevisiae-Escherichia coli Coculture Engineering

Hydroxytyrosol is a valuable plant-derived phenolic compound with excellent pharmacological activities for application in the food and health care industries. Microbial biosynthesis provides a promising approach for sustainable production of hydroxytyrosol via metabolic engineering. However, its efficient production is limited by the machinery and resources available in the commonly used individual microbial platform, for example, Escherichia coli, Saccharomyces cerevisiae. In this study, a S. cerevisiae-E. coli coculture system was designed for de novo biosynthesis of hydroxytyrosol by taking advantage of their inherent metabolic properties, whereby S. cerevisiae was engineered for de novo production of tyrosol based on an endogenous Ehrlich pathway, and E. coli was dedicated to converting tyrosol to hydroxytyrosol by use of native hydroxyphenylacetate 3-monooxygenase (EcHpaBC). To enhance hydroxytyrosol production, intra- and intermodule engineering was employed in this microbial consortium: (I) in the upstream S. cerevisiae strain, multipath regulations combining with a glucose-sensitive GAL regulation system were engineered to enhance the precursor supply, resulting in significant increase of tyrosol production (from 17.60 mg/L to 461.07 mg/L); (II) Echpabc was overexpressed in the downstream E. coli strain, improving the conversion rate of tyrosol to hydroxytyrosol from 0.03% to 86.02%; (III) and last, intermodule engineering with this coculture system was performed by optimization of the initial inoculation ratio of each population and fermentation conditions, achieving 435.32 mg/L of hydroxytyrosol. This S. cerevisiae-E. coli coculture strategy provides a new opportunity for de novo production of hydroxytyrosol from inexpensive feedstock.

Comparative transcriptome and tissue-specific expression analysis of genes reveal tissue-cultured plants as an alternative source for phenylethanoids and phenylpropanoids in Rhodiola imbricata (Edgew.)

Rhodiola imbricata (Crassulaceae) is a traditional trans-Himalayan endangered medicinal herb with immense therapeutic applications. Over the years, over-exploitation, un-managed harvesting, and lack of captive cultivation procedures persuaded threat to its wild habitat. Plant tissue culture and RNA-Seq-based molecular bioprospection of key regulatory genes aid the understanding of molecular dynamics involved in specialized metabolites (phenylethanoids and phenylpropanoids) biosynthesis and its sustainable production. Hence, comparative transcriptomic analysis was performed using leaf and root tissues from the wild and tissue-cultured plants, revealing tissue-specific production of salidroside and rosavin. The transcriptome profiling resulted in 345 million high-quality reads yielding 92,380 unique transcripts with an N₅₀ of 1260 bp. Tissue-specific gene expression analysis revealed that both phenylethanoids and phenylpropanoids biosynthesis are predominantly associated with the shikimate pathway. In addition to RNA-Seq data, the downstream biosynthesis pathways genes viz., phospho-2-dehydro-3-deoxyheptonate aldolase (DAHPS), 3-dehydroquinate synthase (DHQS), shikimate kinase (SK), chorismate mutase (CM), arogenate dehydrogenase (TYRAAT), aromatic-L-amino-acid decarboxylase (TDC), phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4-CL), cinnamoyl-CoA reductase (CCR), and cinnamyl alcohol dehydrogenase (CAD) showed higher expression pattern in wild plant tissues compared to tissue-cultured plants. The transcript fold expression determined by RT-qPCR results followed similar patterns as those observed in RNA-seq and targeted metabolite profiling data. Salidroside and rosavin content in wild plants exhibited 2.40 fold and 1.77 fold increase accumulation compared to the tissue-cultured plant. The present investigation explained the tissue and condition-specific significant differences between the expression of proposed biosynthetic pathway genes and salidroside and rosavin content. Additionally, NAC, bHLH, and ARF were the most abundant transcription factor families found in the transcriptomic analysis of R. imbricata. The generated transcriptome dataset provides a valuable gene(s)/transcription factors hub that can be used for the sustainable production of salidroside and rosavin in R. imbricata under tissue culture conditions.

The effect of in vitro gastrointestinal digestion on the phenolic profiles, bioactivities and bioaccessibility of Rhodiola

Changes in the phenolic profiles and antioxidant and antiproliferative activities of Rhodiola after simulated in vitro digestion were first assessed in this study. Furthermore, permeability and uptake assays as well as RT-qPCR and western blot analyses were performed in order to explore the bioaccessibility of the digesta and its underlying mechanism. The results reveal that in vitro gastrointestinal digestion significantly reduced the total phenolics and total flavonoids as well as the extracellular, cellular antioxidant and antiproliferative activities of Rhodiola, in which the colon digesta had the largest reduction. However, in vitro digestion augmented the cellular uptake rates of Rhodiola phenolics with higher permeability coefficients. The colon digesta (GA-Dig) exhibited the highest uptake of gallic acid (GA, the main compound) instead of GA in its pure form, indicating the synergistic effects of GA and other phenolics in Rhodiola. In-depth mechanistic studies suggest that the fabulous uptake rates and permeability coefficients of the colon digesta were triggered by the down-regulation of the expression levels of ABCF2 mRNA and protein. These findings indicate that simulated gastrointestinal digestion could promote the bioaccessibility and bioactivities of phenolics in Rhodiola.

Salidroside Ameliorates Depression by Suppressing NLRP3-Mediated Pyroptosis via P2X7/NF-κB/NLRP3 Signaling Pathway

Depression is a common and serious mental disorder. Data on its pathogenesis remain unclear and the options of drug treatments are limited. Here, we explored the role of pyroptosis, a novel pro-inflammatory programmed cell death process, in depression as well as the anti-depression effects and mechanisms of salidroside (Sal), a bioactive extract from Rhodiola rosea L. We established a corticosterone (CORT)-induced or lipopolysaccharide (LPS)-induced mice in vivo, and CORT, or nigericin (NLRP3 agonist)-induced PC12 cells in vitro. Our findings demonstrated that Sal profoundly mediated CORT or LPS-induced depressive behavior and improved synaptic plasticity by upregulating the expression of brain-derived neurotrophic factor (BDNF) gene. The data showed upregulation of proteins associated with NLRP3-mediated pyroptosis, including NLRP3, cleaved Caspase-1, IL-1β, IL-18, and cleaved GSDMD. The molecular docking simulation predicted that Sal would interact with P2X7 of the P2X7/NF-κB/NLRP3 signaling pathway. In addition, our findings showed that the NLRP3-mediated pyroptosis was regulated by P2X7/NF-κB/NLRP3 signaling pathway. Interestingly, Sal was shown to ameliorate depression via suppression of the P2X7/NF-κB/NLRP3 mediated pyroptosis, and rescued nigericin-induced pyroptosis in the PC12 cells. Besides, knock down of the NLRP3 gene by siRNA markedly increased the inhibitory effects of Sal on pyroptosis and proinflammatory responses. Taken together, our findings demonstrated that pyroptosis plays a crucial role in depression, and Sal ameliorates depression by suppressing the P2X7/NF-κB/NLRP3-mediated pyroptosis. Thus, our study provides new insights into the potential treatment options for depression.

Enhanced Production of Phenylethanoids Mediated Through Synergistic Approach of Precursor Feeding and Light Regime in Cell Suspension Culture of Rhodiola imbricata (Edgew.)

Precursor feeding is a potential strategy for increasing specialized metabolite production in plant cell culture systems. In the present study, cell suspension cultures were developed and subsequently evaluated for precursor feeding investigations. Cell suspension cultures were established in Murashige and Skoog (MS) medium containing 0.5 mg/L thidiazuron (TDZ) + 1 mg/L α-naphthalene acetic acid (NAA). The growth biomass and metabolite pattern were analyzed to identify specific culture days required for prolific biomass production. The maximum cell dry weight (DW) was observed in leaf cell suspension (1.22 g/100 mL) and root cell suspension culture (1.12 g/100 mL) on day 21. Afterward, the effect of precursor concentrations (tyrosol; 0.5, 1, 2, and 3 mM) along with two light regimes, photoperiod (16L/8D h, 70 µmol/m²/s) and dark (24 h), was evaluated for cell growth and metabolite accumulation. The results revealed that leaf cell suspension treated with 3 mM tyrosol concentration detected maximum salidroside content (26.05 mg/g DW) on day 15, incubated under photoperiod (16L/8D h) condition. Similarly, under photoperiod (16L/8D h), root cell suspension treated with 3 mM tyrosol produced maximum salidroside content (26.62 mg/g DW) on day 12. Moreover, the total phenolics content increased significantly (44.21 mg/g DW) on day 12 in 3 mM tyrosol treatment under photoperiod (16L/8D h). However, precursor concentrations did not influence the total flavonoids content. The present investigation suggests that the immediate pathway precursor, tyrosol, has a strong effect on enhanced production of salidroside, irrespective of explant type and light regimes.

Salidroside Ameliorates Alzheimer's Disease by Targeting NLRP3 Inflammasome-Mediated Pyroptosis

Amyloid β-protein (Aβ) is reported to activate NLRP3 inflammasomes and drive pyroptosis, which is subsequently involved in the pathogenesis of neurodegenerative diseases, such as Alzheimer's disease (AD). To date, the pathogenesis of AD is unfortunately insufficiently elucidated. Therefore, this study was conducted to explore whether Salidroside (Sal) treatment could benefit AD by improving pyroptosis. Firstly, two animal models of AD, induced, respectively, by Aβ1-42 and D-galactose (D-gal)/AlCl₃, have been created to assist our appreciation of AD pathophysiology. We then confirmed that pyroptosis is related to the pathogenesis of AD, and Sal can slow the progression of AD by inhibiting pyroptosis. Subsequently, we established the D-gal and Nigericin-induced PC12 cells injury model in vitro to verify Sal blocks pyroptosis mainly by targeting the NLRP3 inflammasome. For in vivo studies, we observed that Aβ accumulation, Tau hyperphosphorylation, neurons of hippocampal damage, and cognitive dysfunction in AD mice, caused by bilateral injection of Aβ1-42 into the hippocampus and treatments with D-gal combine AlCl₃. Besides, accumulated Aβ promotes NLRP3 inflammasome activation, which leads to the activation and release of a pro-inflammatory cytokine, interleukin-1 beta (IL-1β). Notably, both Aβ accumulation and hyperphosphorylation of Tau decreased and inhibited pyroptosis by downregulating the expression of IL-1β and IL-18, which can be attributed to the treatment of Sal. We further found that Sal can reverse the increased protein expression of TLR4, MyD88, NF-κB, P-NF-κB, NLRP3, ASC, cleaved Caspase-1, cleaved GSDMD, IL-1β, and IL-18 in vitro. The underlying mechanism may be through inhibiting TLR4/NF-κB/NLRP3/Caspase-1 signaling pathway. Our study highlights the importance of NLRP3 inflammasome-mediated pyroptosis in AD, and how the administration of pharmacological doses of Sal can inhibit NLRP3 inflammasome-mediated pyroptosis and ameliorate AD. Thus, we conclude that NLRP3 inflammasome-mediated pyroptosis plays a significant role in AD and Sal could be a therapeutic drug for AD.

Optimization of Biomass Accumulation and Production of Phenolic Compounds in Callus Cultures of Rhodiola rosea L. Using Design of Experiments

Rhodiola rosea L. is a valuable medicinal plant with adaptogenic, neuroprotective, antitumor, cardioprotective, and antidepressant effects. In this study, design of experiments methodology was employed to analyze and optimize the interacting effects of mineral compounds (concentration of NO₃⁻ and the ratio of NH₄⁺ to K⁺) and two plant growth regulators [total 6-benzylaminopurine (BAP) and α-naphthylacetic acid (NAA) concentration and the ratio of BAP to NAA] on the growth and the production of total phenolic compounds (TPCs) in R. rosea calluses. The overall effect of the model was highly significant (p < 0.0001), indicating that NH₄⁺, K⁺, NO₃⁻, BAP, and NAA significantly affected growth. The best callus growth (703%) and the highest production of TPCs (75.17 mg/g) were achieved at an NH₄⁺/K⁺ ratio of 0.33 and BAP/NAA of 0.33, provided that the concentration of plant growth regulators was 30 μM and that of NO₃⁻ was ≤40 mM. According to high-performance liquid chromatography analyses of aerial parts (leaves and stems), in vitro seedlings and callus cultures of R. rosea contain no detectable rosarin, rosavin, rosin, and cinnamyl alcohol. This is the first report on the creation of an experiment for the significant improvement of biomass accumulation and TPC production in callus cultures of R. rosea.

Biosynthesis of a rosavin natural product in Escherichia coli by glycosyltransferase rational design and artificial pathway construction

Phytochemicals are rich resources for pharmaceutical and nutraceutical agents. A key challenge of accessing these precious compounds can present significant bottlenecks for development. The cinnamyl alcohol disaccharides also known as rosavins are the major bioactive ingredients of the notable medicinal plant Rhodiola rosea L. Cinnamyl-(6'-O-β-xylopyranosyl)-O-β-glucopyranoside (rosavin E) is a natural rosavin analogue with the arabinopyranose unit being replaced by its diastereomer xylose, which was only isolated in minute quantity from R. rosea. Herein, we described the de novo production of rosavin E in Escherichia coli. The 1,6-glucosyltransferase CaUGT3 was engineered into a xylosyltransferase converting cinnamyl alcohol monoglucoside (rosin) into rosavin E by replacing the residue T145 with valine. The enzyme activity was further elevated 2.9 times by adding the mutation N375Q. The synthesis of rosavin E from glucose was achieved with a titer of 92.9 mg/L by combining the variant CaUGT3^T145V/N375Q, the UDP-xylose synthase from Sinorhizobium meliloti 1021 (SmUXS) and enzymes for rosin biosynthesis into a phenylalanine overproducing E. coli strain. The production of rosavin E was further elevated by co-overexpressing UDP-xylose synthase from Arabidopsis thaliana (AtUXS3) and SmUXS, and the titer in a 5 L bioreactor with fed-batch fermentation reached 782.0 mg/L. This work represents an excellent example of producing a natural product with a disaccharide chain by glycosyltransferase engineering and artificial pathway construction.

West meets east: open up a dialogue on phytomedicine

The desire to extend the wisdom of traditional health systems has motivated the trade of many phytomedicine on a global scale for centuries, especially some dietary herbs, making a great overlap exits between western and eastern phytomedicine. Despite the communication since ancient times, a key disconnect still exists in the dialog among western and eastern herbal researchers. There is very little systematic effort to tap into the friction and fusion of eastern and western wisdom in utilizing phytomedicine. In this review, we analyzed the similarities and differences of three representative phytomedicine, namely Rhodiola, seabuckthorn, and fenugreek, aiming to open up new horizons in developing novel health products by integrating the wisdom of the east and the west.

Quality Evaluation of Randomized Controlled Trials of Rhodiola Species: A Systematic Review

Background

Rhodiola is a worldwide used medicinal plant for its various medicinal functions, and the number of randomized controlled trials (RCTs) of Rhodiola is increasing in recent years. This study aims to evaluate the reporting quality and risk of bias of the current RCT reports of different Rhodiola species.

Methods

Six databases including Embase, PubMed, Web of Science, the Cochrane Library, ClinicalTrial.gov, and China National Knowledge Infrastructure were searched to identify RCTs that used Rhodiola as a single intervention and were published in English or Chinese from inception to December 2020. The Consolidated Standards of Reporting Trials (CONSORT) 2010 statement was used as the checklist for assessment, and a scoring system was applied to the evaluation of RCTs. Score 0 represents no reporting or inadequate reporting, and score 1 represents adequate reporting. The risk of bias of the included studies was also assessed using the Cochrane Risk of Bias tool.

Results

A total of 39 RCTs were included in this study, including 23 RCTs of Rhodiola rosea (R. rosea), 8 RCTs of Rhodiola crenulata (R. crenulata), and 8 RCTs of Rhodiola wallichiana (R. wallichiana). None of the included studies met all the CONSORT statement criteria, and the reporting quality of RCTs of the three Rhodiola species was all generally poor. Based on the risk of bias assessment, the majority of included studies were judged to have an unclear risk of bias in most domains due to inadequate reporting.

Conclusions

There is inadequate reporting among the included RCTs of different Rhodiola species, and RCTs of Rhodiola with higher reporting quality and better methodological quality are needed.

Salidroside: A review of its recent advances in synthetic pathways and pharmacological properties

Salidroside has been identified as one of the most potent compounds isolated from various Rhodiola plants, which have been used for a long time as adaptogens in traditional Chinese medicine. However, due to the severe growing environment of herbal medicine and large-scale excavation, the content of natural salidroside is extremely small. Most of the previous studies focused on herbal medicine, and there were few reviews on the synthesis of its main active ingredient salidroside. This paper presents different synthetic routes of salidroside to resolve the contradiction between supply and demand and lays the foundation for new drug research and development. Furthermore, emerging evidence indicates that salidroside, a promising environmentally-adapted drug with low toxicity and few side effects, possesses a wide spectrum of pharmacological properties, including activities on the cardiovascular system and central nervous system, anti-hypoxia, anti-fatigue and anti-aging activities, anticancer activity, anti-inflammatory activity, antioxidant activity, antivirus and immune stimulation activities, antidiabetic activity, anti-osteoporotic activity, and so on. Although the former researches have summarized the pharmacological effects of salidroside, focusing on the central nervous system, diabetes, and cancer, the overall pharmacological aspects of it have not been analyzed. This review highlights biological characteristics and mechanisms of action from 2009 to now as well as toxicological and pharmacokinetic data of the analyzed compound reported so far, with a view to providing a reference for further development and utilization of salidroside.

Salidroside as a potential neuroprotective agent for ischemic stroke: a review of sources, pharmacokinetics, mechanism and safety

Salidroside (Sal) is a bioactive extract principally from traditional herbal medicine such as Rhodiola rosea L., which has been commonly used for hundreds of years in Asia countries. The excellent neuroprotective capacity of Sal has been illuminated in recent studies. This work focused on the source, pharmacokinetics, safety and anti-ischemic stroke (IS) effect of Sal, especially emphasizing its mechanism of action and BBB permeability. Extensive databases, including Pubmed, Web of science (WOS), Google Scholar and China National Knowledge Infrastructure (CNKI), were applied to obtain relevant online literatures. Sal exerts powerful therapeutic effects on IS in experimental models either in vitro or in vivo due to its neuroprotection, with significantly diminishing infarct size, preventing cerebral edema and improving neurological function. Also, the findings suggest the underlying mechanisms involve anti-oxidation, anti-inflammation and anti-apoptosis by regulating multiple signaling pathways and key molecules, such as NF-κB, TNF-α and PI3K/Akt pathway. In pharmacokinetics, although showing a rapid absorption and elimination, bioavailability of Sal is elevated under some non-physiological conditions. The component and its metabolite (tyrosol) are capable of distributing to brain tissue and the later keeps a higher level of concentration. Moreover, Sal scarcely has obvious toxicity or side effects in a variety of animal experiments and clinical trials, but combination of drugs and perinatal use of medicine should be taken more attentions. Finally, as an active ingredient, not only is Sal isolated from diverse plants with limited yield, but also large batches of the products can be harvested by biological and chemical synthesis. With higher efficacy and better safety profiles, Sal could sever as a promising neuroprotectant for preventing and treating IS. Nevertheless, further investigations are still required to explore the pharmacodynamic and pharmacokinetic properties of Sal in the treatment of IS.

Neuroprotective Effects of Salidroside in a Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD), the most common form of dementia worldwide, is characterized by pathological hallmarks like β-amyloid peptide (Aβ) and clinical manifestations including cognitive impairment, psychiatry disorders, and behavioral changes. Salidroside (Sal) extracted from Rhodiola rosea L. showed protective effects against Aβ-induced neurotoxicity in a Drosophila AD model in our previous research. In the present study, daily doses of Sal were administered to APP/PS1 mice, a mouse model of AD, and several parameters were tested, including behavioral performance, Aβ status, levels of synapse-related proteins, and levels of PI3K/Akt targets of mTOR cell signaling pathway proteins. The behavioral testing showed an improvement in locomotor activity in the APP/PS1 mice after the administration of Sal. Treatment with Sal decreased both the soluble and insoluble Aβ levels and increased the expression of PSD95, NMDAR1, and calmodulin-dependent protein kinase II. The phosphatidylinositide PI3K/Akt/mTOR signaling was upregulated, which was in accordance with the above improvements from Sal treatment. Our findings suggested that Sal may protect the damaged synapses of the neurons in the APP/PS1 mice.

Identification of microRNAs and relative target genes in Moringa oleifera leaf and callus

MicroRNAs, a class of small, non-coding RNAs, play important roles in plant growth, development and stress response by negatively regulating gene expression. Moringa oleifera Lam. plant has many medical and nutritional uses; however, little attention has been dedicated to its potential for the bio production of active compounds. In this study, 431 conserved and 392 novel microRNA families were identified and 9 novel small RNA libraries constructed from leaf, and cold stress treated callus, using high-throughput sequencing technology. Based on the M. oleifera genome, the microRNA repertoire of the seed was re-evaluated. qRT-PCR analysis confirmed the expression pattern of 11 conserved microRNAs in all groups. MicroRNA159 was found to be the most abundant conserved microRNA in leaf and callus, while microRNA393 was most abundantly expressed in the seed. The majority of predicted microRNA target genes were transcriptional factors involved in plant reproduction, growth/development and abiotic/biotic stress response. In conclusion, this is the first comprehensive analysis of microRNAs in M. oleifera leaf and callus which represents an important addition to the existing M. oleifera seed microRNA database and allows for possible exploitation of plant microRNAs induced with abiotic stress, as a tool for bio-enrichment with pharmacologically important phytochemicals.

Producing Gram-Scale Unnatural Rosavin Analogues from Glucose by Engineered Escherichia coli

Cinnamyl alcohol glycosides (CAGs) are key active ingredients of the precious medicinal plant Rhodiola rosea L., which has diverse pharmacological activities. The quality of R. rosea extracts is standardized to the contents of rosavin, a cinnamyl alcohol disaccharide, along with salidroside. The supply of rosavin and analogues is limited by both the inefficiency of chemical synthesis methods and the shortage of natural resources. Herein, we achieved de novo synthesis of a series of rosavin analogues by engineered Escherichia coli strains. First, cinnamyl alcohol was synthesized by expression of phenylalanine ammonia-lyase (PAL), hydroxycinnamate:CoA ligase, and cinnamyl-CoA reductase in a phenylalanine high-producing strain. UGT73C5 from Arabidopsis thaliana and a sugar chain elongating glycosyltransferase from Catharanthus roseus, CaUGT3 sequentially catalyzed the formation of an unnatural cinnamyl alcohol diglucoside, named rosavin B. Then, these biosynthetic enzymes were transformed into a tyrosine high-producing strain, except that PAL was replaced by a tyrosine ammonia-lyase, and synthesis of mono- and diglucosides of p-coumaryl alcohol with sugars attached to aliphatic or phenolic hydroxyl position was achieved. Finally, fed-batch fermentation was conducted for the strain producing rosavin B, and the titer reached 4.7 g/L. Tri- and tetraglucosides of cinnamyl alcohol were also produced by fed-batch fermentation. In summary, seven rosavin analogues including six unnatural compounds were produced from glucose by microorganisms. This work expanded the structural diversity of CAGs, which holds promise to discover new analogues with improved pharmaceutical properties. The study also paves the way for producing CAGs in a sustainable and cheap way.

Salidroside protects SH‑SY5Y from pathogenic α‑synuclein by promoting cell autophagy via mediation of mTOR/p70S6K signaling

The abnormal aggregation of α‑synuclein (α‑syn), which is an important pathological feature of Parkinson's disease (PD), is cytotoxic to dopaminergic neurons and causes cellular damage and apoptosis. Salidroside (SAL) is the main active component of the traditional Chinese medicine Rhodiola rosea. Previous research has demonstrated that SAL exerts cellular protection against cell senescence and neurodegeneration. However, the role and mechanism of action of SAL in PD remain unclear. The present study used overexpression of the wild‑type and the A53T mutation of α‑syn to induce a neuronal model of PD in SH‑SY5Y cells, which led to neuronal toxicity and a reduced cell proliferation index. SAL increased the cell proliferation index of both PD model groups in a dose‑dependent manner. Additionally, SAL alleviated pathogenic phosphorylated (Ser129) α‑syn expression as well as the ratio of microtubule‑associated proteins 1A/1B light chain 3 (LC3)‑I to LC3‑II expression, which is related to autophagic function. Furthermore, the results suggested that the underlying mechanism for the SAL‑induced protection of PD model neurons may involve the preservation of autophagy, which attenuates the phosphorylation of α‑syn in neurons predominantly via mTOR/p70S6K, and is independent of the PI3K/Akt signaling pathway.

GRP78/BIP/HSPA5 as a Therapeutic Target in Models of Parkinson's Disease: A Mini Review

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by selective loss of dopamine neurons in the substantia nigra pars compacta of the midbrain. Reports from postmortem studies in the human PD brain, and experimental PD models reveal that endoplasmic reticulum (ER) stress is implicated in the pathogenesis of PD. In times of stress, the unfolded or misfolded proteins overload the folding capacity of the ER to induce a condition generally known as ER stress. During ER stress, cells activate the unfolded protein response (UPR) to handle increasing amounts of abnormal proteins, and recent evidence has demonstrated the activation of the ER chaperone GRP78/BiP (78 kDa glucose-regulated protein/binding immunoglobulin protein), which is important for proper folding of newly synthesized and partly folded proteins to maintain protein homeostasis. Although the activation of this protein is essential for the initiation of the UPR in PD, there are inconsistent reports on its expression in various PD models. Consequently, this review article aims to summarize current knowledge on neuroprotective agents targeting the expression of GRP78/BiP in the regulation of ER stress in experimental PD models.

Identification of Glutathione Peroxidase (GPX) Gene Family in Rhodiola crenulata and Gene Expression Analysis under Stress Conditions

Glutathione peroxidases (GPXs) are important enzymes in the glutathione-ascorbate cycle for catalyzing the reduction of H₂O₂ or organic hydroperoxides to water. GPXs play an essential role in plant growth and development by participating in photosynthesis, respiration, and stress tolerance. Rhodiola crenulata is a popular traditional Chinese medicinal plant which displays an extreme energy of tolerance to harsh alpine climate. The GPXs gene family might provide R. crenulata for extensively tolerance to environment stimulus. In this study, five GPX genes were isolated from R. crenulata. The protein amino acid sequences were analyzed by bioinformation softwares with the results that RcGPXs gene sequences contained three conserve cysteine residues, and the subcellular location predication were in the chloroplast, endoplasmic reticulum, or cytoplasm. Five RcGPXs members presented spatial and temporal specific expression with higher levels in young and green organs. And the expression patterns of RcGPXs in response to stresses or plant hormones were investigated by quantitative real-time PCR. In addition, the putative interaction proteins of RcGPXs were obtained by yeast two-hybrid with the results that RcGPXs could physically interact with specific proteins of multiple pathways like transcription factor, calmodulin, thioredoxin, and abscisic acid signal pathway. These results showed the regulation mechanism of RcGPXs were complicated and they were necessary for R. crenulata to adapt to the treacherous weather in highland.

Salidroside mitigates hypoxia/reoxygenation injury by alleviating endoplasmic reticulum stress‑induced apoptosis in H9c2 cardiomyocytes

Endoplasmic reticulum (ER) stress-induced apoptosis serves a crucial role in the development of myocardial ischemia/reperfusion (I/R) injury. Salidroside is a phenylpropanoid glycoside isolated from Rhodiola rosea L., which is a plant often used in traditional Chinese medicine. It possesses multiple pharmacological actions and protects against myocardial I/R injury in vitro and in vivo. However, it is not yet clear whether ER stress or ER stress-induced apoptosis contributes to the cardioprotective effects of salidroside against myocardial I/R injury. Hence, hypoxia/reoxygenation (H/R)-treated H9c2 cardiomyocytes were used in the current study to mimic myocardium I/R injury in vivo. It was hypothesized that salidroside alleviates ER stress and ER stress-induced apoptosis, thereby reducing H/R injury in H9c2 cells. The results demonstrated that salidroside attenuated H/R-induced H9c2 cardiomyocyte injury, as cell viability was increased, lactate dehydrogenase release was decreased, morphological changes in apoptotic cells were ameliorated and the apoptosis ratio was reduced compared with the H/R group. ER stress was reversed, indicated by the downregulation of glucose regulated protein 78 and C/EBP homologous protein following pretreatment with salidroside. In addition, salidroside attenuated ER stress-induced apoptosis, as the expression of cleaved caspase-12 and pro-apoptotic protein Bcl-2 associated X protein and activity of caspase-3 was decreased, while the expression of anti-apoptotic protein Bcl-2 was increased following pretreatment with salidroside. Furthermore, the results indicated that salidroside decreases the activation of the ER stress-associated signaling pathway, as the expression of phosphorylated protein kinase RNA (PKR)-like ER kinase (p-PERK) and phosphorylated inositol-requiring enzyme-1α (p-IRE1α) proteins were decreased following pretreatment with salidroside. These results demonstrate that salidroside protects against H/R injury via regulation of the PERK and IRE1α pathways, resulting in alleviation of ER stress or ER stress-induced apoptosis in H9c2 cardiomyocytes.

Enhanced Production of Phenolic Compounds in Compact Callus Aggregate Suspension Cultures of Rhodiola imbricata Edgew

Rhodiola imbricata is a rare medicinal plant of the trans-Himalayan region of Ladakh. It is used for the treatment of numerous health ailments. Compact callus aggregate (CCA) suspension cultures of Rhodiola imbricata were established to counter extinction threats and for production of therapeutically valuable phenolic compounds to meet their increasing industrial demands. The present study also investigated the effect of jasmonic acid (JA) on production of phenolic compounds and bioactivities in CCA suspension cultures. CCA suspension cultures established in an optimized Murashige and Skoog medium supplemented with 30 g/l sucrose, 3 mg/l NAA, and 3 mg/l BAP showed maximum biomass accumulation (8.43 g/l DW) and highest salidroside production (3.37 mg/g DW). Upon 100 μM JA treatment, salidroside production (5.25 mg/g DW), total phenolic content (14.69 mg CHA/g DW), total flavonoid content (4.95 mg RE/g DW), and ascorbic acid content (17.93 mg/g DW) were significantly increased in cultures. In addition, DPPH-scavenging activity (56.32%) and total antioxidant capacity (60.45 mg QE/g DW) were significantly enhanced upon JA treatment, and this was positively correlated with increased accumulation of phenolic compounds. JA-elicited cultures exhibited highest antimicrobial activity against Escherichia coli. This is the first report describing the enhanced production of phenolic compounds and bioactivities from JA-elicited CCA suspension cultures of Rhodiola imbricata.

Pharmacological activities, mechanisms of action, and safety of salidroside in the central nervous system

The primary objective of this review article was to summarize comprehensive information related to the neuropharmacological activity, mechanisms of action, toxicity, and safety of salidroside in medicine. A number of studies have revealed that salidroside exhibits neuroprotective activities, including anti-Alzheimer's disease, anti-Parkinson's disease, anti-Huntington's disease, anti-stroke, anti-depressive effects, and anti-traumatic brain injury; it is also useful for improving cognitive function, treating addiction, and preventing epilepsy. The mechanisms underlying the potential protective effects of salidroside involvement are the regulation of oxidative stress response, inflammation, apoptosis, hypothalamus-pituitary-adrenal axis, neurotransmission, neural regeneration, and the cholinergic system. Being free of side effects makes salidroside potentially attractive as a candidate drug for the treatment of neurological disorders. It is evident from the available published literature that salidroside has potential use as a beneficial therapeutic medicine with high efficacy and low toxicity to the central nervous system. However, the definite target protein molecules remain unclear, and clinical trials regarding this are currently insufficient; thus, guidance for further research on the molecular mechanisms and clinical applications of salidroside is urgent.

Influence of light quality on growth, secondary metabolites production and antioxidant activity in callus culture of Rhodiola imbricata Edgew

Rhodiola imbricata is a rare medicinal herb well-known for its adaptogenic and antioxidant properties due to the presence of a diverse array of secondary metabolites, including phenylethanoids and phenylpropanoids. These secondary metabolites are generating considerable interest due to their potential applications in pharmaceutical and nutraceutical industries. The present study investigated the influence of light quality on growth, production of industrially important secondary metabolites and antioxidant activity in callus cultures of Rhodiola imbricata. Callus cultures of Rhodiola imbricata were established under different light conditions: 100% red, 100% blue, 100% green, RGB (40% red: 40% green: 20% blue) and 100% white (control). The results showed that the callus cultures grown under red light accumulated maximum amount of biomass (7.43 g/l) on day 21 of culture, as compared to other light conditions. Maximum specific growth rate (0.126 days^-1) and doubling time (132.66 h) was observed in callus cultures grown under red light. Reverse phase-high performance liquid chromatographic (RP-HPLC) analysis revealed that the callus cultures exposed to blue light accumulated maximum amount of Salidroside (3.12 mg/g DW) on day 21 of culture, as compared to other light conditions. UV-Vis spectrophotometric analysis showed that the callus cultures exposed to blue light accumulated maximum amount of total phenolics (11.84 mg CHA/g DW) and total flavonoids (5.53 mg RE/g DW), as compared to other light conditions. Additionally, callus cultures grown under blue light displayed enhanced DPPH free radical scavenging activity (53.50%). Callus cultures grown under different light conditions showed no significant difference in ascorbic acid content (11.05-13.90 mg/g DW) and total antioxidant capacity (27.37-30.17 mg QE/g DW). The correlation analysis showed a positive correlation between total phenolic content and DPPH free radical scavenging activity in callus cultures (r = 0.85). Taken together, these results demonstrate the remarkable potential of light quality on biomass accumulation and production of industrially important secondary metabolites in callus cultures of Rhodiola imbricata. This study will open new avenues and perspectives towards abiotic elicitation strategies for sustainable growth and enhanced production of bioactive compounds in in-vitro cultures of Rhodiola imbricata.

Salidroside Protects Against Advanced Glycation End Products-Induced Vascular Endothelial Dysfunction

Background

Salidroside, the major active compound in Rhodiola, has been reported to provide beneficial effects on cardiovascular diseases, but its effects on diabetes-induced vascular endothelial dysfunction are less known. Here, we examined the protective effects of salidroside on endothelial function in diabetes and explored the potential underlying mechanism.

Material/Methods

First, we assessed the endothelium-dependent relaxation response to acetylcholine, with or without salidroside treatment, in aortas isolated from Sprague-Dawley rats. Then, cell viability, oxidative biomarkers, and protein expression were tested to determine the effect of salidroside treatment on human umbilical vein endothelial cells (HUVECs) in vitro.

Results

Advanced glycation end product (AGE)-induced endothelial dysfunction was significantly improved by salidroside treatment (P<0.05), as shown by a reduced relaxation response to the vasodilator acetylcholine. Further, incubation with salidroside restored NO levels and reduced reactive oxygen species formation in AGE-stimulated HUVECs in a concentration-dependent manner (P<0.05). We also showed that nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/heme oxygenase 1 (HO-1) and nuclear factor kappa B (NF-κB) signaling was critical for the salidroside-mediated beneficial regulation.

Conclusions

Our results demonstrate that salidroside protects against AGE-induced endothelial dysfunction, and its effects may be in part attributed to the induction of HO-1 and attenuation of phosphorylated NF-κB p65.

SIRT1 mediates salidroside-elicited protective effects against MPP+ -induced apoptosis and oxidative stress in SH-SY5Y cells: involvement in suppressing MAPK pathways

Parkinson's disease (PD) is a progressive neurodegenerative disease, leading to tremor, rigidity, bradykinesia, and gait impairment. Salidroside has been reported to exhibit antioxidative and neuroprotective properties in PD. However, the underlying neuroprotective mechanisms effects of salidroside are poorly understood. Recently, a growing body of evidences suggest that silent information regulator 1 (SIRT1) plays important roles in the pathophysiology of PD. Hence, the present study investigated the roles of SIRT1 in neuroprotective effect of salidroside against N-methyl-4-phenylpyridinium (MPP⁺ )-induced SH-SY5Y cell injury. Our findings revealed that salidroside attenuates MPP⁺ -induced neurotoxicity as evidenced by the increase in cell viability, and the decreases in the caspase-3 activity and apoptosis ratio. Simultaneously, salidroside pretreatment remarkably increased SIRT1 activity, SIRT1 mRNA and protein levels in MPP⁺ -treated SH-SY5Y cell. However, sirtinol, a SIRT1 activation inhibitor, significantly blocked the inhibitory effects of salidroside on MPP⁺ -induced cytotoxicity and apoptosis. In addition, salidroside abolished MPP⁺ -induced the production of reactive oxygen species (ROS), the up-regulation of NADPH oxidase 2 (NOX2) expression, the down-regulations of superoxide dismutase (SOD) activity and glutathione (GSH) level in SH-SY5Y cells, while these effects were also blocked by sirtinol. Finally, we found that the inhibition of salidroside on MPP⁺ -induced phosphorylation of p38, extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) were also reversed by sirtinol in SH-SY5Y cells. Taken together, these results indicated that SIRT1 contributes to the neuroprotection of salidroside against MPP⁺ -induced apoptosis and oxidative stress, in part through suppressing of mitogen-activated protein kinase (MAPK) pathways.

Rhodiola rosea L.: an herb with anti-stress, anti-aging, and immunostimulating properties for cancer chemoprevention

Purpose of review

Rhodiola rosea extracts have been used as a dietary supplement in healthy populations, including athletes, to non-specifically enhance the natural resistance of the body to both physical and behavior stresses for fighting fatigue and depression. We summarize the information with respect to the new pharmacological activities of Rhodiola rosea extracts and its underlying molecular mechanisms in this review article.

Recent findings

In addition to its multiplex stress-protective activity, Rhodiola rosea extracts have recently demonstrated its anti-aging, anti-inflammation, immunostimulating, DNA repair and anti-cancer effects in different model systems. Molecular mechanisms of Rhodiola rosea extracts's action have been studied mainly along with one of its bioactive compounds, salidroside. Both Rhodiola rosea extracts and salidroside have contrast molecular mechanisms on cancer and normal physiological functions. For cancer, Rhodiola rosea extracts and salidroside inhibit the mTOR pathway and reduce angiogenesis through down-regulation of the expression of HIF-1α/HIF-2α. For normal physiological functions, Rhodiola rosea extracts and salidroside activate the mTOR pathway, stimulate paracrine function and promote neovascularization by inhibiting PHD3 and stabilizing HIF-1α proteins in skeletal muscles. In contrast to many natural compounds, salidroside is water-soluble and highly bioavailable via oral administration and concentrated in urine by kidney excretion.

Summary

Rhodiola rosea extracts and salidroside can impose cellular and systemic benefits similar to the effect of positive lifestyle interventions to normal physiological functions and for anti-cancer. The unique pharmacological properties of Rhodiola rosea extracts or salidroside deserve further investigation for cancer chemoprevention, in particular for human urinary bladder cancer.

Production of Cinnamyl Alcohol Glucoside from Glucose in Escherichia coli

Rosin, a cinnamyl alcohol glucoside, is one of the important ingredients in Rhodiola rosea, which is a valuable medicinal herb used for centuries. Rosin displayed multiple biological activities. The traditional method for producing rosin and derivatives is direct extraction from R. rosea, which suffers from limited availability of natural resources and complicated purification procedure. This work achieved de novo biosynthesis of rosin in Escherichia coli. First, a biosynthetic pathway of aglycon cinnamyl alcohol from phenylalanine was constructed. Subsequently, the UGT genes from Rhodiola sachalinensis (UGT73B6) or Arabidopsis thaliana (UGT73C5) were introduced into the above recombinant E. coli strain to produce rosin. Then the phenylalanine metabolic pathway of E. coli was optimized by genetic manipulation, and the production of rosin by the engineered E. coli reached 258.5 ± 8.8 mg/L. This study lays a significant foundation for microbial production of rosin and its derivatives using glucose as the renewable carbon source.

Salidroside, a Bioactive Compound of Rhodiola Rosea, Ameliorates Memory and Emotional Behavior in Adult Mice

Rhodiola Rosea (R. Rosea) is a plant used in traditional popular medicine to enhance cognition and physical performance. R. Rosea medicinal properties have been related to its capability to act as an adaptogen, i.e., a substance able to increase the organism's resistance to a variety of chemical, biological, and physical stressors in a non-specific way. These adaptogen properties have been mainly attributed to the glycoside salidroside, one of the bioactive compounds present in the standardized extracts of R. Rosea. Here, we aimed to investigate whether a single dose of salidroside is able to affect memory and emotional behavior in wild type adult mice. We performed fear conditioning to assess cued and contextual memory, elevated plus maze and open field to evaluate anxiety, and tail suspension test to evaluate depression. Our results showed that a single i.p. administration of salidroside was able to enhance fear memory and exerted an anxiolytic and antidepressant effect. These data confirmed the adaptogenic effect of R. Rosea bioactive compounds in animal models and suggest that salidroside might represent an interesting pharmacological tool to ameliorate cognition and counteract mood disorders.

Neuroprotective effects of salidroside through PI3K/Akt pathway activation in Alzheimer's disease models

Alzheimer’s disease (AD) is a devastating neurodegenerative disorder characterized by deposits of aggregated amyloid-β (Aβ) peptide and neurofibrillary tangles in the brain parenchyma. Despite considerable research to elucidate the pathological mechanisms and identify therapeutic strategies for AD, effective treatments are still lacking. In the present study, we found that salidroside (Sal), a phenylpropanoid glycoside isolated from Rhodiola rosea L., can protect against Aβ-induced neurotoxicity in four transgenic Drosophila AD models. Both longevity and locomotor activity were improved in Sal-fed Drosophila. Sal also decreased Aβ levels and Aβ deposition in brain and ameliorated toxicity in Aβ-treated primary neuronal culture. The neuroprotective effect of Sal was associated with upregulated phosphatidylinositide 3-kinase (PI3K)/Akt signaling. Our findings identify a compound that may possess potential therapeutic benefits for AD and other forms of neurodegeneration.