Triterpenoid saponins from Dipsacus asper and their activities in vitro

Full-length transcriptome, proteomics and metabolite analysis reveal candidate genes involved triterpenoid saponin biosynthesis in Dipsacus asperoides

Dipsacus asperoides is a traditional medicinal herb widely used in inflammation and fracture in Asia. Triterpenoid saponins from D. asperoides are the main composition with pharmacological activity. However, the biosynthesis pathway of triterpenoid saponins has not been completely resolved in D. asperoides. Here, the types and contents of triterpenoid saponins were discovered with different distributions in five tissues (root, leaf, flower, stem, and fibrous root tissue) from D. asperoides by UPLC-Q-TOF-MS analysis. The discrepancy between five tissues in D. asperoides at the transcriptional level was studied by combining single-molecule real-time sequencing and next- generation sequencing. Meanwhile, key genes involved in the biosynthesis of saponin were further verified by proteomics. In MEP and MVA pathways, 48 differentially expressed genes were identified through co-expression analysis of transcriptome and saponin contents, including two isopentenyl pyrophosphate isomerase and two 2,3-oxidosqualene β-amyrin cyclase, etc. In the analysis of WGCNA, 6 cytochrome P450s and 24 UDP- glycosyltransferases related to the biosynthesis of triterpenoid saponins were discovered with high transcriptome expression. This study will provide profound insights to demonstrate essential genes in the biosynthesis pathway of saponins in D. asperoides and support for the biosynthetic of natural active ingredients in the future.

Traditional uses, processing methods, phytochemistry, pharmacology and quality control of Dipsacus asper Wall. ex C.B. Clarke: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Dipsacus asper Wall. ex C.B. Clarke, a traditional Chinese herbal medicine, has long been used in China for the therapy of bone diseases (e.g. bone fracture, osteoporosis, rheumatic arthritis), traumatic hematoma, uterine bleeding and those caused by the deficiency of liver and kidney.

AIM OF THE STUDY

This work aims to evaluate current research progress on chemical constituents, pharmacological activities, quality control, and pharmacokinetic of Dipsacus asper Wall. ex C.B. Clarke, pinpoint the shortcomings of existing studies, and provide meaningful guidelines for our future investigations.

METHODS

Extensive database retrieval, such as PubMed, SciFinder and CNKI, was carried out by using keywords such as "Dipsacus asper", "Radix Dipsaci", and "Xuduan". Furthermore, relevant textbooks, patents, reviews, and digital documents were consulted to collate all available scientific literature and to provide a complete science-based survey of the topic.

RESULTS

More than 100 compounds have been isolated and identified from Dipsacus asper Wall. ex C.B. Clarke, a substantial proportion of which were reported to be triterpenoids and iridoids. Biological effects such as protective effects against bone fracture, anti-osteoporosis, neuroprotective, cardioprotective, anti-aging and protection of reproductive system activities were also evaluated in vitro and in vivo.

CONCLUSIONS

Diaphoretic processing resulted in the drop in the content of asperosaponin VI, which was highly associated with bone protective effect of DA. Therefore, diaphoretic processing was not a suitable processing method for DA. Although Dipsacus asper Wall. ex C.B. Clarke was traditionally used for therapy of osteoarthritis, the in-depth study of the underlying mechanism was very rare. Much endeavor had been made on the effect of DA on bone fracture. Notably, high-dose of Dipsacus asper administration may cause adverse impacts in maternal healthy and embryo-fetal development. It's not suitable for further development in those bioactivities, such as anti-inflammatory and free radical scavenging, which are shared in many other plant species. Pharmacological effects of individual component of DA is not equivalent to its traditional usage. Attention should be paid to the traditional effect of extract of DA.

Comparative Proteomic Analysis of Dipsacus asperoides Roots from Different Habitats in China

Dipsacus asperoides is a kind of Chinese herbal medicine with beneficial health properties. To date, the quality of D. asperoides from different habitats has shown significant differences. However, the molecular differences in D. asperoides from different habitats are still unknown. The aim of this study was to investigate the differences in protein levels of D. asperoides from different habitats. Isobaric tags for relative and absolute quantification (iTRAQ) and 2DLC/MS/MS were used to detect statistically significant changes in D. asperoides from different habitats. Through proteomic analysis, a total of 2149 proteins were identified, of which 42 important differentially expressed proteins were screened. Through in-depth analysis of differential proteins, the protein metabolism energy and carbohydrate metabolism of D. asperoides from Hubei Province were strong, but their antioxidant capacity was weak. We found that three proteins, UTP-glucose-1-phosphate uridylyltransferase, allene oxide cyclase, and isopentyl diphosphate isomerase 2, may be the key proteins involved in dipsacus saponin VI synthesis. Eight proteins were found in D. asperoides in response to environmental stress from different habitats. Quantitative real-time PCR analysis confirmed the accuracy and authenticity of the proteomic analysis. The results of this study may provide the basic information for exploring the cause of differences in secondary metabolites in different habitats of D. asperoides and the protein mechanism governing differences in quality.

Triterpenoids and triterpenoid saponins from Dipsacus asper and their cytotoxic and antibacterial activities

Phytochemical investigation of the ethyl acetate soluble part, generated from the ethanol extract of the roots of Dipsacus asper, led to the separation and identification of three undescribed triterpenoids including one arborinane type, one ursane type and one oleanane type, two unreported oleanane type triterpenoid arabinoglycosides, and 18 known analogues. Structures of these compounds were determined by comprehensive spectroscopic analyses, with the absolute configurations of 25-acetoxy-28-dehydroxyrubiarbonone E and 2α,3β-dihydroxy-23-norurs-4(24),11,13(18)-trien-28-oic acid being established by evaluation of their experimental and calculated ECD spectra. 25-Acetoxy-28-dehydroxyrubiarbonone E features an oxygenated C-25 that is the first case among arborinane type triterpenoids, while 2α,3β,24-trihydroxy-23-norurs-12-en-28-oic acid incorporates a sp³ C-24 that is a rare structural feature of 23-norursane type triterpenoids. Of these isolates, 2',4'-O-diacetyl-3-O-α-l-arabinopyranosyl-23-hydroxyolea-12-en-28-oic acid and hederagonic acid exhibited moderate antibacterial activity against Staphylococcus aureus with IC₅₀ values of 12.3 and 10.3 μM, respectively, while those with either a feruloyloxy group or an arabinosyl moiety at C-3 displayed potent cytotoxic activities against four tumor cell lines A549, H157, HepG2 and MCF-7.

Genome-Wide Transcriptional Excavation of Dipsacus asperoides Unmasked both Cryptic Asperosaponin Biosynthetic Genes and SSR Markers

BACKGROUND

Dipsacus asperoides is a traditional Chinese medicinal crop. The root is generally used as a medicine and is frequently prescribed by Chinese doctors for the treatment of back pain, limb paralysis, flutter trauma, tendon injuries, and fractures. With the rapid development of bioinformatics, research has been focused on this species at the gene or molecular level. For purpose of fleshing out genome information about D. asperoides, in this paper we conducted transcriptome analysis of this species.

PRINCIPAL FINDINGS

To date, many genes encoding enzymes involved in the biosynthesis of triterpenoid saponins in D.asperoides have not been elucidated. Illumina paired-end sequencing was employed to probe D. asperoides's various enzymes associated with the relevant mesostate. A total of 30, 832,805 clean reads and de novo spliced 43,243 unigenes were obtained. Of all unigenes, only 8.27% (3578) were successfully annotated in total of seven public databases: Nr, Nt, Swiss-Prot, GO, KOG, KEGG, and Pfam, which might be attributed to the poor studies on D. asperoides. The candidate genes encoding enzymes involved in triterpenoid saponin biosynthesis were identified and experimentally verified by reverse transcription qPCR, encompassing nine cytochrome P450s and 17 UDP-glucosyltransferases. Specifically, unearthly putative genes involved in the glycosylation of hederagenin were acquired. Simultaneously, 4490 SSRs from 43,243 examined sequences were determined via bioinformatics analysis.

CONCLUSION

This study represents the first report on the use of the Illumina sequence platform on this crop at the transcriptome level. Our findings of candidate genes encoding enzymes involved in Dipsacus saponin VI biosynthes is provide novel information in efforts to further understand the triterpenoid metabolic pathway on this species. The initial genetics resources in this study will contribute significantly to the genetic breeding program of D. asperoides, and are beneficial for clinical diagnosis and treatment.

New Lignans and Iridoid Glycosides from Dipsacus asper Wall

Six new compounds, including four new lignans, dipsalignan A (1), B–D (3–5), and two new bis-iridoid glycoside dimmers, dipsanosides M (7) and N (8), together with two known compounds (2) and (6), have been isolated from the roots of Dipsacus asper Wall. Their structures were established on the basis of spectroscopic data (MS, 1D, 2D NMR, and CD) and chemical methods. All the isolated compounds were tested against human immunodeficiency virus-1 (HIV-1) integrase inhibition activities, and only compounds 1, 2, 7, and 8 displayed weak activities.

Triterpenoids

This review covers the isolation and structure determination of triterpenoids including squalene derivatives, lanostanes, holostanes, cycloartanes, cucurbitanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes, onoceranes and saponins; 308 references are cited.