Plastome structure, phylogenomics and evolution of plastid genes in Swertia (Gentianaceae) in the Qing-Tibetan Plateau

BACKGROUND

The genus Swertia is of great medicinal importance and one of the most taxonomically challenging taxa within Gentianaceae, largely due to the morphological similarities of species within this genus and with its closely related genera. Previous molecular studies confirmed its polyphyly but suffered from low phylogenetic resolutions because only limited sequence loci were used. Thus, we conducted the structural, gene evolutionary, and phylogenetic analyses of 11 newly obtained plastomes of Swertia. Our result greatly improved the phylogenetic resolutions in Swertia, shed new light on the plastome evolution and phylogenetic relationships of this genus.

RESULTS

The 11 Swertia plastomes together with the published seven species proved highly similar in overall size, structure, gene order, and content, but revealed some structural variations caused by the expansion and contraction of the IRb region into the LSC region, due to the heterogeneous length of the ψycf1. The gene rps16 was found to be in a state flux with pseudogenes or completely lost. Similar situation was also documented in other genera of Gentianaceae. This might imply loss of the gene in the common ancestor of Gentianaceae. The distribution plot of ENC vs. GC3 showed all these plastomes arranging very close in the Wright line with an expected ENC value (49-52%), suggesting the codon usage of Swertia was mainly constrained by a GC mutation bias. Most of the genes remained under the purifying selection, however, the cemA was identified under positive selection, possibly reflecting an adaptive response to low CO₂ atmospheric conditions during the Late Miocene. Our phylogenomic analyses, based on 74 protein-coding genes (CDS), supported the polyphyly of Swertia with its close allies in the subtribe Swertiinae, presumably due to recent rapid radiation. The topology inferred from our phylogenetic analyses partly supported the current taxonomic treatment. Finally, several highly variable loci were identified, which can be used in future phylogenetic studies and accurate identification of medicinal genuineness of Swertia.

CONCLUSIONS

Our study confirmed the polyphyly of Swertia and demonstrated the power of plastome phylogenomics in improvement of phylogenetic resolution, thus contributing to a better understanding of the evolutionary history of Swertia.

Optimization of salicylic acid and chitosan treatment for bitter secoiridoid and xanthone glycosides production in shoot cultures of Swertia paniculata using response surface methodology and artificial neural network

BACKGROUND

In this study, response surface methodology (RSM) and artificial neural network (ANN) was used to construct the predicted models of linear, quadratic and interactive effects of two independent variables viz. salicylic acid (SA) and chitosan (CS) for the production of amarogentin (I), swertiamarin (II) and mangiferin (III) from shoot cultures of Swertia paniculata Wall. These compounds are the major therapeutic metabolites in the Swertia plant, which have significant role and demand in the pharmaceutical industries.

RESULTS

Present study highlighted that different concentrations of SA and CS elicitors substantially influenced the % yield of (I), (II) and (III) compounds in the shoot culture established on modified ½ MS medium (supplemented with 2.22 mM each of BA and KN and 2.54 mM NAA). In RSM, different response variables with linear, quadratic and 2 way interaction model were computed with five-factor-three level full factorial CCD. In ANN modelling, 13 runs of CCD matrix was divided into 3 subsets, with approximate 8:1:1 ratios to train, validate and test. The optimal enhancement of (I) (0.435%), (II) (4.987%) and (III) (4.357%) production was achieved in 14 days treatment in shoot cultures of S. paniculata elicited by 9 mM and 12 mg L^- 1 concentrations (SA) and (CS).

CONCLUSIONS

In optimization study, (I) show 0.170-0.435%; (II) display 1.020-4.987% and (III) upto 2.550-4.357% disparity with varied range of SA (1-20 mM) and CS (1-20 mg L^- 1). Overall, optimization of elicitors to promote secoiridoid and xanthone glycoside production with ANN modeling (r² = 100%) offered more significant results as compared to RSM (r² = 99.8%).

Phylogeography of Swertia perennis in Europe based on cpDNA markers

Background

Swertia perennis(Gentianaceae) is a perennial diploid and clonal plant species that is discontinuously distributed in peat bogs in the mountains of Europe, Asia and North America as well as in the lowlands of Europe. The current geographical dispersion of S. perennis is probably the result of quaternary climatic changes that have played an important role in determining the distribution of Swertia and other plant and animal species.

Methods

In this study we used molecular techniques and combined data from chloroplast DNA markers (trnLF region and trnH-psbA spacer) to elucidate the phylogeography of S. perennis in Europe. Plants were collected from 28 populations in different locations in the lowlands and mountainous areas of Europe (e.g., the Carpathians, Sudetes, Bohemian Forest and Alps). cDNA was analysed to detect the genetic relationship between specimens from different locations.

Results

A total of 20 haplotypes were identified across the dataset. They were characterised by a high level of genetic variability but showed a lack of phylogeographical structure. This pattern may be the result of repeated recolonization and expansion from several areas. Such genetic differentiation may also be attributed to the relatively long-term isolation of S. perennis in Pleistocene refugia in Europe, which resulted in independent separation of different cpDNA phylogenetic lineages and variation in the nucleotide composition of cpDNA.

Discussion

The lack of strong phylogeographical structure makes it impossible to indicate the centre of haplotype diversity; however, refugia located in the Carpathians, Sudetes or Alps are the most probable sites where S. perennis existed in Europe. This lack of structure may also indicate a high level of gene flow in times when the landscape and fen systems were not fragmented in numerous geographically-isolated populations. This makes it difficult to speculate about the relationships between Asiatic and European plant populations and the origin and distribution of this species in Europe. Today, it seems to be restricted due to the occurrence of plants which clearly reflects the genetic variability from the ancient period.

Xanthones Content in Swertia multicaulis D. Don from Nepal

The medicinal plant Swertia multicaulis D. Don was collected in Rasuwa District (Nepal) and the xanthone content of its ethyl acetate extracts was studied. The total amount of xanthones in S. multicaulis determined by HPLC reaches almost 13 g of xanthones per 1 kg of dry matter. The identification of xanthones in S. multicaulis was achieved by a combination of HPLC, LC–MS and LC–NMR. The final assignment of the individual chemical structures was provided by NMR, supported by preparative HPLC. In eight chromatographic peaks, four major xanthones were identified—1,3-dihydroxy-5,8-dimethoxyxanthone, 1-hydroxy-3,5,8-trimethoxyxanthone, bellidifolin (1,5,8-tri-hydroxy-3-methoxyxanthone), and decussatin (1-hydroxy-3,7,8-trimethoxyxanthone).

Reverse Phase-ultra Flow Liquid Chromatography-diode Array Detector Quantification of Anticancerous and Antidiabetic Drug Mangiferin from 11 Species of Swertia from India

Background:

Genus Swertia is valued for its great medicinal potential, mainly Swertia chirayita (Roxb. ex Fleming) H. Karst. is used in traditional medicine for a wide range of diseases. Mangiferin one of xanthoids is referred with enormous pharmacological potentials.

Objective:

The aim of the study was to quantify and compare the anticancerous and antidiabetic drug mangiferin from 11 Swertia species from India. The study also evaluates hierarchical relationships between the species based on mangiferin content using multivariate analysis.

Materials and Methods:

The reverse phase-ultra flow liquid chromatography-diode array detector analyses was performed and chromatographic separation was achieved on a Lichrospher 100, C18e (5 μm) column (250–4.6 mm). Mobile phase consisting of 0.2% triethylamine (pH-4 with O-phosphoric acid) and acetonitrile (85:15) was used for separation with injection volume 20 μL and detection wave length at 257 nm.

Results:

Results indicated that concentration of mangiferin has been found to vary largely between Swertia species collected from different regions. Content of mangiferin was found to be highest in Swertia minor compared to other Swertia species studied herein from the Western Ghats and Himalayan region also. The same was also evident in the multivariate analysis, wherein S. chirayita, S. minor and Swertia paniculata made a separate clade.

Conclusion:

Conclusively, the work herein provides insights of mangiferin content from 11 Swertia species of India and also presents their hierarchical relationships. To best of the knowledge this is the first report of higher content of mangiferin from any Swertia species.

SUMMARY

The present study quantifies and compares mangiferin in 11 species of Swertia from India. The study also evaluates hierarchical relationships between the species based on mangiferin content using multivariate analysis. The mangiferin content was highest in S. minor compared to the studied Swertia species. To the best of our knowledge this is the first report of higher content of mangiferin from Swertia species.

Abbreviations used: LOD: Limit of detection, LOQ: Limit of quantification, RP-UFLC-DAD: Reverse phase-ultra flow liquid chromatography-diode array detector, RSD: Relative standard deviation, SAN: Swertia angustifolia, SAP: Swertia angustifolia var. pulchella, SBI: S. bimaculata, SCH: S. chirayita, SCO: S. corymbosa, SDE: S. densifolia, SDI: S. dialatata, SLA: S. lawii, SMI: S. minor; SNE: S. nervosa, and SPA: S. paniculata

RP-HPLC analysis of seco-iridoid glycoside swertiamarin from different Swertia species

Genus Swertia is valued for its great medicinal potential; mainly Swertia chirayita (Roxb. ex Fleming) H. Karst. is used in traditional medicine for a wide range of diseases. Seco-iridoid glycosides like swertiamarin is referred with enormous pharmacological potentials. The aim of the study was to identify a suitable substitute to S. chirayita by quantifying seco-iridoid swertiamarin from five different Swertia species endemic to the Western Ghats. The reverse-phase high-performance liquid chromatography diode array detector analyses were performed and chromatographic separation was achieved on a Lichrospher 100, C18e (5 µm) column (250-4.6 mm). A mobile phase consisting of acetonitrile and water (25:75) was used for separation. Results indicated that the concentration of the marker compound has been found to vary largely between and within the species from different localities. The content of swertiamarin was the highest in S. chirayita compared to the other species studied herein, advocating the use of Swertia minor as an alternate source to S. chirayita.

Quantitative determination of three pentacyclic triterpenes from five Swertia L. species endemic to Western Ghats, India, using RP-HPLC analysis

Aim of this study was to identify pentacyclic triterpenoids betulinic acid (BA), oleanolic acid (OA) and ursolic acid (UA) from five Swertia species endemic to Western Ghats, which are used as substitutes as well as adulterants to Swertia chirayita. Our results indicate that the concentration of active compound vary largely among and within the species from different localities. OA was found in a higher amount in all species compared to BA and UA. From the results, it was clear that BA, OA and UA are present in the endemic species collected from Western Ghats, thus advocating the use of these species as alternate sources to S. chirayita. This in due course may release pressure of exploitation from natural resources of S. chirayita and help to bring it out from an endangered category from conservation point of view.

Characterization of metabolites of sweroside in rat urine using ultra-high-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry and NMR spectroscopy

Sweroside, a major active iridoid in Swertia pseudochinensis Hara, is recognized as an effective agent in the treatment of liver injury. Based on previous reports, the relatively short half-life (64 min) and poor bioavailability (approximately 0.31%) in rats suggested that not only sweroside itself but also its metabolites could be responsible for the observed hepato-protective effect. However, few studies have been carried out on the metabolism of sweroside. Therefore, the present study aimed at identifying the metabolites of sweroside in rat urine after a single oral dose (100 mg/kg). With ultra-high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC/Q-TOF-MS), the metabolic profile revealed 11 metabolites in rat urine, including phase I, phase II and aglycone-related products. The chemical structures of metabolites were proposed based on accurate mass measurements of protonated or deprotonated molecules and their fragmentation patterns. Our findings showed that the aglycone of sweroside (M05) and its glucuronide conjugate (M06) were principal circulating metabolites in rats. While several other metabolic transformations, occurring via reduction, N-heterocyclization and N-acetylation after deglycosylation, were also observed. Two metabolites (M05 and M06) were isolated from the rat urine for structural elucidation and identifcation of reaction sites. Both M05 and M06 were characterized by (1)H, (13)C and two-dimensional nuclear magnetic resonance (NMR) spectroscopy. UHPLC/Q-TOF-MS analysis has provided an important analytical platform to gather metabolic profile of sweroside.