Synthesis and antitumor activity of des-AB analogue of steroidal saponin OSW-1

Identification of genetic variants controlling diosgenin content in Dioscorea zingiberensis tuber by genome-wide association study

BACKGROUND

Diosgenin is an important steroidal precursor renowned for its diverse medicinal uses. It is predominantly sourced from Dioscorea species, particularly Dioscorea zingiberensis. Dioscorea zingiberensis has an ability to accumulate 2-16% diosgenin in its rhizomes. In this study, a diverse population of 180 D. zingiberensis accessions was used to evaluate the genomic regions associated with diosgenin biosynthesis by the genome wide association study approach (GWAS).

RESULTS

The whole population was characterized for diosgenin contents from tubers by gas chromatography mass spectrometry. The individuals were genotyped by the genotyping-by-sequencing approach and 10,000 high-quality SNP markers were extracted for the GWAS. The highest significant marker-trait-association was observed as an SNP transversion (G to T) on chromosome 10, with 64% phenotypic variance explained. The SNP was located in the promoter region of CYP94D144 which is a member of P450 gene family involved in the independent biosynthesis of diosgenin from cholesterol. The transcription factor (TF) binding site enrichment analysis of the promoter region of CYP94D144 revealed NAC TF as a potential regulator. The results were further validated through expression profiling by qRT-PCR, and the comparison of high and low diosgenin producing hybrids obtained from a bi-parental population.

CONCLUSIONS

This study not only enhanced the understanding of the genetic basis of diosgenin biosynthesis but also serves as a valuable reference for future genomic investigations on CYP94D144, with the aim of augmenting diosgenin production in yam tubers.

Chemical Synthesis of Saponins

Saponins are a large family of amphiphilic glycosides of steroids and triterpenes found in plants and some marine organisms. By expressing a large diversity of structures on both sugar chains and aglycones, saponins exhibit a wide range of biological and pharmacological properties and serve as major active principles in folk medicines, especially in traditional Chinese medicines. Isolation of saponins from natural sources is usually a formidable task due to the microheterogeneity of saponins in Nature. Chemical synthesis can provide access to large amounts of natural saponins as well as congeners for understanding their structure-activity relationships and mechanisms of action. This article presents a comprehensive account on chemical synthesis of saponins. First highlighted are general considerations on saponin synthesis, including preparation of aglycones and carbohydrate building blocks, assembly strategies, and protecting-group strategies. Next described is the state of the art in the synthesis of each type of saponins, with an emphasis on those representative saponins having sophisticated structures and potent biological activities.

Genome survey sequencing of Dioscorea zingiberensis

Dioscorea zingiberensis (Dioscoreceae) is the main plant source of diosgenin (steroidal sapogenins), the precursor for the production of steroid hormones in the pharmaceutical industry. Despite its large economic value, genomic information of the genus Dioscorea is currently unavailable. Here, we present an initial survey of the D. zingiberensis genome performed by next-generation sequencing technology together with a genome size investigation inferred by flow cytometry. The whole genome survey of D. zingiberensis generated 31.48 Gb of sequence data with approximately 78.70× coverage. The estimated genome size is 800 Mb, with a high level of heterozygosity based on K-mer analysis. These reads were assembled into 334 288 contigs with a N50 length of 1079 bp, which were further assembled into 92 163 scaffolds with a total length of 173.46 Mb. A total of 4935 genes, 81 tRNAs, 69 rRNAs, and 661 miRNAs were predicted by the genome analysis, and 263 484 repeated sequences were obtained with 419 372 simple sequence repeats (SSRs). Among these SSRs, the mononucleotide repeat type was the most abundant (up to 54.60% of the total SSRs), followed by the dinucleotide (29.60%), trinucleotide (11.37%), tetranucleotide (3.53%), pentanucleotide (0.65%), and hexanucleotide (0.25%) repeat types. The 1C-value of D. zingiberensis was calibrated against Salvia miltiorrhiza and calculated as 0.87 pg (851 Mb) by flow cytometry, which was very close to the result of the genome survey. This is the first report of genome-wide characterization within this taxon.

Natural product analogues: towards a blueprint for analogue-focused synthesis

A review of approaches to natural product analogues leads to the suggestion of new methods for the generation of biologically active natural product-like scaffolds.

Methodology for the Construction of the Bicyclo[4.3.0]nonane Core

The bicyclo[4.3.0]nonane scaffold, commonly known as a hydrindane, is a common structural motif found in many terpenoid structures and one that remains a challenge for synthetic chemists to elaborate with appropriate regio- and stereo-selectivity. Over the course of the study of terpene natural products, the elaboration of the hydrindane structure has seen progress on the utilization of both old and newer methods to achieve the desired outcomes. This review seeks to serve as a general overview of these methods, and detail specific examples.

Chemical synthesis of saponins

Saponins are a large family of amphiphilic glycosides of steroids and triterpenes found in plants and some marine organisms. By expressing a large diversity of structures on both sugar chains and aglycones, saponins exhibit a wide range of biological and pharmacological properties and serve as major active principles in folk medicines, especially in traditional Chinese medicines. Isolation of saponins from natural sources is usually a formidable task due to the microheterogeneity of saponins in Nature. Chemical synthesis can provide access to large amounts of natural saponins as well as congeners for understanding their structure-activity relationships and mechanisms of action. This article presents a comprehensive account on chemical synthesis of saponins. First highlighted are general considerations on saponin synthesis, including preparation of aglycones and carbohydrate building blocks, assembly strategies, and protecting-group strategies. Next described is the state of the art in the synthesis of each type of saponins, with an emphasis on those representative saponins having sophisticated structures and potent biological activities.

De novo transcriptome assembly and the putative biosynthetic pathway of steroidal sapogenins of Dioscorea composita

The plant Dioscorea composita has important applications in the medical and energy industries, and can be used for the extraction of steroidal sapogenins (important raw materials for the synthesis of steroidal drugs) and bioethanol production. However, little is known at the genetic level about how sapogenins are biosynthesized in this plant. Using Illumina deep sequencing, 62,341 unigenes were obtained by assembling its transcriptome, and 27,720 unigenes were annotated. Of these, 8,022 unigenes were mapped to 243 specific pathways, and 531 unigenes were identified to be involved in 24 secondary metabolic pathways. 35 enzymes, which were encoded by 79 unigenes, were related to the biosynthesis of steroidal sapogenins in this transcriptome database, covering almost all the nodes in the steroidal pathway. The results of real-time PCR experiments on ten related transcripts (HMGR, MK, SQLE, FPPS, DXS, CAS, HMED, CYP51, DHCR7, and DHCR24) indicated that sapogenins were mainly biosynthesized by the mevalonate pathway. The expression of these ten transcripts in the tuber and leaves was found to be much higher than in the stem. Also, expression in the shoots was low. The nucleotide and protein sequences and conserved domains of four related genes (HMGR, CAS, SQS, and SMT1) were highly conserved between D. composita and D. zingiberensis; but expression of these four genes is greater in D. composita. However, there is no expression of these key enzymes in potato and no steroidal sapogenins are synthesized.

Biology-oriented synthesis of a withanolide-inspired compound collection reveals novel modulators of hedgehog signaling

Biology-oriented synthesis employs the structural information encoded in complex natural products to guide the synthesis of compound collections enriched in bioactivity. The trans-hydrindane dehydro-δ-lactone motif defines the characteristic scaffold of the steroid-like withanolides, a plant-derived natural product class with a diverse pattern of bioactivity. A withanolide-inspired compound collection was synthesized by making use of three key intermediates that contain this characteristic framework derivatized with different reactive functional groups. Biological evaluation of the compound collection in cell-based assays that monitored biological signal-transduction processes revealed a novel class of Hedgehog signaling inhibitors that target the protein Smoothened.