Systematic characterization and simultaneous quantification of the multiple components of Rhododendron dauricum based on high-performance liquid chromatography with quadrupole time-of-flight tandem mass spectrometry

Chemistry, biosynthesis, and theranostics of antioxidant flavonoids and polyphenolics of genus Rhododendron: an overview

The genus Rhododendron is an ancient and most widely distributed genus of the family Ericaceae consisting of evergreen plant species that have been utilized as traditional medicine since a very long time for the treatment of various ailments including pain, asthma, inflammation, cold, and acute bronchitis. The chemistry of polyphenolics isolated from a number of species of the genus Rhododendron has been investigated. During the currently designed study, an in-depth study on the phytochemistry, natural distribution, biosynthesis, and pharmacological properties including their potential capability as free radical scavengers has been conducted. This work provides structural characteristics of phenolic compounds isolated from the species of Rhododendron with remarkable antioxidant potential. In addition, biosynthesis and theranostic study have also been encompassed with the aims to furnish a wide platform of valuable information for designing of new drug entities. The detailed information including names, structural features, origins, classification, biosynthetic pathways, theranostics, and pharmacological effects of about 171 phenolics and flavonoids isolated from the 36 plant species of the genus Rhododendron with the antioxidant potential has been covered in this manuscript. This study demonstrated that species of Rhododendron genus have excellent antioxidant activities and great potential as a source for natural health products. This comprehensive review might serve as a foundation for more investigation into the Rhododendron genus.

Farrerol suppresses epithelial-mesenchymal transition in hepatocellular carcinoma via suppression of TGF-β1/Smad2/3 signaling

BACKGROUND

Epithelial-mesenchymal transition (EMT) is an essential process for the metastasis of multiple malignancies, including hepatocellular carcinoma (HCC). Farrerol is a plant-derived flavonoid and has significant pharmacological effects. However, the anticancer activities of farrerol have not been fully elucidated. Here, we investigated the effects of farrerol on HCC progression.

METHODS

The potential of farrerol to prevent HCC cell migration and invasiveness was evaluated by wound healing and transwll matrix assays. Immunoblotting, immunofluorescence, and qPCR were used to detect the levels of EMT-related proteins. Transforming growth factor beta (TGF-β) (10 ng/ml) was used to stimulate HCC cells, followed by measurement of cell migration, invasiveness, and the EMT. TGF-β1/Smads signaling was examined by immunoblotting. A xenograft mouse model was used to assess the anticancer efficacy of farrerol in vivo. The expression levels of EMT- and angiogenesis-related proteins in xenograft tumors were evaluated by immunoblotting or immunohistochemistry.

RESULTS

We found that farrerol blocked HCC cell migration and invasiveness. Farrerol upregulated E-cadherin levels and reduced N-cadherin and vimentin levels. Farrerol also downreuglated the expression levels of EMT-related transcription factors including slug, snail, twist, and zeb1. Furthermore, farrerol suppressed TGF-β-stimulated migration, invasiveness, and the EMT in HCC cells. The phosphorylation of Smad 2/3 induced by TGF-β was inhibited by farrerol. Importantly, farrerol suppressed HCC growth and the EMT in vivo. Farrerol also inhibited tumor angiogenesis by inhibiting hypoxia-inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF) in vivo.

CONCLUSION

Overall, farrerol suppresss HCC by inhibiting migration, invasiveness, the EMT, and angiogenesis, implying that farrerol could be a promising antimetastasis agent for HCC.

Integrated metabolomics and transcriptomics reveal molecular mechanisms of corolla coloration in Rhododendron dauricum L

Rhododendron dauricum L. is a semi-evergreen shrub of high ornamental and medicinal values in Northeast China. To study the molecular mechanisms of corolla coloration in R. dauricum, integrated metabolomics and transcriptomics were performed in R. dauricum featuring purple flowers and R. dauricum var. album featuring white flowers. Comparative metabolomics revealed 25 differential metabolites in the corolla of the two distinct colors, enriched in flavonoids that are closely related to pigmentation in the flower. Differential analysis of the transcriptomics data revealed enrichment of structural genes for flavonoid biosynthesis (99 up- and 58 down-regulated, respectively, in purple corollas compared to white ones). Significantly, CHS and CHI, key genes in the early stage of anthocyanin synthesis, as well as F3H, F3'H, F3'5'H, DFR, ANS, and UFGT that promote the accumulation of pigments in the late stage of anthocyanin synthesis, were up-regulated in R. dauricum (purple color). In R. dauricum var. album, FLS were key genes determining the accumulation of flavonols. In addition, transcriptome-metabolome correlation analysis identified 16 R2R3 MYB transcription factors (out of 83 MYBs) that are important for corolla coloration. Five negative and four positive MYBs were further identified by integrated transcriptional and metabolic network analysis, revealing a key role of MYBA and MYB12 in regulating anthocyanins and flavonols, respectively. Moreover, we validated the function of RdMYBA by creating stable transgenic plants and found that RdMYBA promotes anthocyanin biosynthesis. In summary, we systematically characterized the transcriptome and metabolome of two R. dauricum cultivars with different flower colors and identified MYBs as key factors in modulating corolla coloration.

Traditional uses, phytochemistry, pharmacology, toxicology, and quality control of Rhododendron dauricum L. leaves: A comprehensive review

ETHNOPHARMACOLOGICAL RELEVANCE

Rhododendron dauricum L. is a traditional herb mainly distributed in the northeast China, Mongolia, Korea Peninsula, and Russia Far East. The dried leaves of Rhododendron dauricum L. (LRD), generally known "Man Shan Hong" have been traditionally applied as folk medicines to treat fever, copious phlegm, asthma, acute and chronic bronchitis, sore throat, dysentery, diabetes mellitus, cancer, and hypertension. To date, no comprehensive review on R. dauricum leaves has been published.

AIM OF THE STUDY

Recent progresses in traditional use, phytochemistry, pharmacology, toxicology, and quality control of R. dauricum leaves are systematically presented and critically evaluated in order to provide scientifical basis for its reasonable utilization and further study.

MATERIALS AND METHODS

All information about R. dauricum leaves were retrieved from internet scientific databases including Sci-Finder, Web of Science, PubMed, CNKI, Google Scholar, Elsevier, Wiley, ACS publications, SpringerLink, and the Chinese Pharmacopoeia between 1970 and 2022. Plant names were validated by "The Plant List" (http://www.theplantlist.org/).

RESULTS

So far, 114 structurally diverse compounds have been isolated and identified from LRD, mainly including flavonoids, diterpenoids, triterpenoids, meroterpenoids, phenols, and 54 volatile components were identified from the essential oils of LRD. Among these, flavonoids are considered as characteristic components and major bioactive phytochemicals. The crude extracts and compounds from LRD have been reported to possess broad pharmacological effects including antitussive and expectorant, anti-inflammatory, anti-HIV, antibacterial, and cytotoxic effects, etc. CONCLUSIONS: As a traditional herb medicine, LRD have been used popularly. On the one hand, traditional uses of LRD provide valuable directions for current research; on the other hand, modern phytochemical and pharmacological studies verify the traditional uses to make its reasonable utilization. However, several defects such as active components determination, in vivo and clinical pharmacological evaluation, toxicology assessment, and quality control of LRD need further study.

A preliminary study of the chemical composition and bioactivity of Bombax ceiba L. flower and its potential mechanism in treating type 2 diabetes mellitus using ultra-performance liquid chromatography quadrupole-time-flight mass spectrometry and network pharmacology analysis

This study aimed to preliminary investigate the phytochemistry, bioactivity, hypoglycemic potential, and mechanism of action of Bombax ceiba L. flower (BCF), a wild edible and food plant in China. By using methanol extraction and liquid-liquid extraction, the crude extract (CE) of BCF and its petroleum ether (PE), dichloromethane (DCM), ethyl acetate (EtOAc), n-butanol (n-BuOH), and aqueous (AQ) fractions were obtained, and their chemical components and biological activities were evaluated. Further high-performance liquid chromatography (HPLC) analysis was carried out to identify and quantify the active constituents of BFC and its five fractions, and the phytochemical composition of the best-performing fraction was then analyzed by ultra-performance liquid chromatography quadrupole-time-flight mass spectrometry (UPLC/Q-TOF-MS). Finally, a network pharmacology strategy based on the chemical profile of this fraction was applied to speculate its main hypoglycemic mechanism. Results revealed the excellent biological activities of BCF, especially the EtOAc fraction. In addition to the highest total flavonoid content (TFC) (367.72 μg RE/mg E) and total phenolics content (TPC) (47.97 μg GAE/mg E), EtOAc showed the strongest DPPH⋅ scavenging ability (IC₅₀ value = 29.56 μg/mL), ABTS⋅⁺ scavenging ability (IC₅₀ value = 84.60 μg/mL), and ferric reducing antioxidant power (FRAP) (889.62 μg FeSO₄/mg E), which were stronger than the positive control BHT. EtOAc also exhibited the second-best α-glucosidase inhibitory capacity and second-best acetylcholinesterase (AChE) inhibitory capacity with the IC₅₀ values of 2.85 and 3.27 mg/mL, respectively. Also, EtOAc inhibited HepG2, MCF-7, Raw264.7, and A549 cell with IC₅₀ values of 1.08, 1.62, 0.77, and 0.87 mg/mL, which were the second or third strongest in all fractions. Additionally, HPLC analysis revealed significant differences in the compounds’ abundance between different fractions. Among them, EtOAc had the most detected compounds and the highest content. According to the results of UPLC/Q-TOF-MS, 38 compounds were identified in EtOAc, including 24 phenolic acids and 6 flavonoids. Network pharmacological analysis further confirmed 41 potential targets of EtOAc in the treatment of type 2 diabetes, and intracellular receptor signaling pathways, unsaturated fatty acid, and DNA transcription pathways were the most possible mechanisms. These findings suggested that BCF was worthwhile to be developed as an antioxidant and anti-diabetic food/drug.

Farrerol exhibits inhibitory effects on lung adenocarcinoma cells by activating the mitochondrial apoptotic pathway

Farrerol is an herbal compound extracted from rhododendron. Here, our study is to investigate biological effects of farrerol on lung adenocarcinoma (LAC) cells. Human LAC cell lines and xenograft mouse model were utilized to define the effects of farrerol on tumor growth. Our findings indicated that farrerol significantly reduced LAC cell viability as well as the colony-forming capacity. Flow cytometry analysis demonstrated that farrerol contributed to cell apoptosis and G0/G1 phase cell cycle arrest. Mechanistically, farrerol treatment upregulated proapoptotic molecules (Bak, Bid, cleaved caspase-3 and cleaved caspase-9) and senescence markers (p16 and p2), but downregulated antiapoptosis genes (Bcl-2 and Bcl-XL) and cell cycle-associated genes (CyclinD1 and CDK4); meanwhile, the phosphorylation of retinoblastoma (Rb) protein was attenuated upon pretreatment of LAC cells with farrerol in comparison to untreated control. Further studies indicated that farrerol elevated reactive oxygen species levels, activating mitochondrial apoptotic pathway and causing cell apoptosis. However, exposure to farrerol did not result in significant apoptosis in normal lung epithelial cells, suggesting a tumor-specific effect of farrerol on LAC cells. In animal model, farrerol showed a significant inhibitory effect on LAC xenograft tumor growth. And gene expressions in tumor tissues, as mentioned above, were in line with the in vitro results. Taken together, these results suggested that farrerol caused LAC cell apoptosis by activating mitochondrial apoptotic pathway, whereas farrerol treatment had no notable effect on normal lung epithelial cells. Farrerol might be an effective therapeutic drug for LAC.

Kangaroo Island propolis types originating from two Lepidosperma species and Dodonaea humilis

The endemic Australian plants Lepidosperma sp. Flinders Chase (Cyperaceae), Lepidosperma viscidum (Cyperaceae) and Dodonaea humilis (Sapindaceae) were found to be the botanical origin of three propolis types found on Kangaroo Island identified by TLC and ¹H NMR matching of propolis and plant resin analytical profiles. Resin samples extracted from the plant, Lepidosperma sp. Flinders Chase, were chromatographically fractionated to give: methyl 3-phenyl-2-(E-cinnamoyloxy)propanoate (1), 3-(E-8-methoxy-8-oxo-3,7-dimethyloct-2-enyl)-4-hydroxy-E-cinnamic acid (2), 3-(E-6,7-dihydroxy-3,7-dimethyloct-2-enyl)-4-hydroxy-E-cinnamic acid (3), previously undescribed; and the known stilbenes, 2-prenyl-3,5-dihydroxy-E-stilbene (6) and 2-prenyl-3-methoxy-5-hydroxy-E-stilbene (7). The resin from L. viscidum gave: 5'-(E-4-hydroxy-3-methylbut-2-enyl)-4,2',4'-trihydroxydihydrochalcone (4); 5'-(E-4-hydroxy-3-methylbut-2-enyl)-4'-methoxy-4,2'-dihydroxydihydrochalcone (5), previously undescribed; and three known flavanones, farrerol (8), 5,7,3',5'-tetrahydroxy-6,8-dimethylflavanone (9) and 5,7,3',5'-tetrahydroxy-6-methylflavanone (10). The major constituent in the propolis identified as being sourced from D. humilis was identified as 6,8-diprenyl-5,7,3',4'-tetrahydroxyflavanone (11), a known compound identified in several unrelated plant species.

A new pentacyclic triterpenoid from the leaves of Rhododendron dauricum L. with inhibition of NO production in LPS-induced RAW 264.7 cells

A new pentacyclic triterpenoid, 3-oxo-urs-11,13(18)-dien-28-oic acid (1), along with twelve known triterpenoids, α-amyrin (2), 19α-hydroxy-α-amyrin (3), triptohypol E (4), uvaol (5), 2α,3α-dihydroxyurs-11-en-13β,28-olide (6), 3β-hydroxyurs-11-en-13β,28-olide (7), ursolic acid (8), asiatic acid (9), oleanolic acid (10), aegiceradienol (11), obtusalin (12) and betulinic acid (13) were isolated from the leaves of Rhododendron dauricum L. Their structures were established from spectroscopic data and comparison with reported values. Among them, compounds 3, 4, 6, 7 and 11 were isolated from the Ericaceae family for the first time. Compounds 2, 5, 9, 12 and 13 were obtained from R. dauricum for the first time. Additionally, compounds 6, 10 and 11 significantly inhibited the levels of NO in LPS-stimulated RAW 264.7 cells at 3 μM.

Organ-Specific Metabolic Shifts of Flavonoids in Scutellaria baicalensis at Different Growth and Development Stages

Scutellaria baicalensis Georgi is a traditional Chinese herbal medicine mainly containing flavonoids that contribute to its bioactivities. In this study, the distributions and dynamic changes of flavonoid levels in various organs of S. baicalensis at different development stages were investigated by UHPLC-QTOF-MS/MS and HPLC-DAD methods. The results indicated that the metabolic profiles of S. baicalensis changed with growth and development. During the initial germination stage, the seeds mainly contained flavonols. With growth, the main kinds of flavonoids in S. baicalensis changed from flavonols to flavanones and flavones. The results also revealed that the accumulation of flavonoids in S. baicalensis is organ-specific. The flavones without 4′-OH groups mainly accumulate in the root and the flavanones mainly accumulate in aerial organs. Dynamic accumulation analysis showed that the main flavonoids in the root of S. baicalensis accumulated rapidly before the full-bloom stage, then changed to a small extent. The results suggested the proper harvest time for the aerial parts was at the initial stage of reproductive growth and the flower buds should be collected before flowering. This study deepening the knowledge of S. baicalensis should provide valuable information for guiding the scientific cultivation of this plant and the development and utilization of S. baicalensis.