Phylogeny of Caragana (Fabaceae) based on DNA sequence data from rbcL, trnS–trnG, and ITS

Chloroplast genomes of Caragana tibetica and Caragana turkestanica: structures and comparative analysis

BACKGROUND

The genus Caragana encompasses multiple plant species that possess medicinal and ecological value. However, some species of Caragana are quite similar in morphology, so identifying species in this genus based on their morphological characteristics is considerably complex. In our research, illumina paired-end sequencing was employed to investigate the genetic organization and structure of Caragana tibetica and Caragana turkestanica, including the previously published chloroplast genome sequence of 7 Caragana plants.

RESULTS

The lengths of C. tibetica and C. turkestanica chloroplast genomes were 128,433 bp and 129,453 bp, respectively. The absence of inverted repeat sequences in these two species categorizes them under the inverted repeat loss clade (IRLC). They encode 110 and 111 genes (4 /4 rRNA genes, 30 /31tRNA genes, and 76 /76 protein-coding genes), respectively. Comparison of the chloroplast genomes of C. tibetica and C. turkestanica with 7 other Caragana species revealed a high overall sequence similarity. However, some divergence was observed between certain intergenic regions (matK-rbcL, psbD-psbM, atpA-psbI, and etc.). Nucleotide diversity (π) analysis revealed the detection of five highly likely variable regions, namely rps2-atpI, accD-psaI-ycf4, cemA-petA, psbN-psbH and rpoA-rps11. Phylogenetic analysis revealed that C. tibetica's sister species is Caragana jubata, whereas C. turkestanica's closest relative is Caragana arborescens.

CONCLUSIONS

The present study provides worthwhile information about the chloroplast genomes of C. tibetica and C. turkestanica, which aids in the identification and classification of Caragana species.

Multiple configurations of the plastid and mitochondrial genomes of Caragana spinosa

MAIN CONCLUSION

In this study, we assembled the complete plastome and mitogenome of Caragana spinosa and explored the multiple configurations of the organelle genomes. Caragana spinosa belongs to the Papilionoidea subfamily and has significant pharmaceutical value. To explore the possible interaction between the organelle genomes, we assembled and analyzed the plastome and mitogenome of C. spinosa using the Illumina and Nanopore DNA sequencing data. The plastome of C. spinosa was 129,995 bp belonging to the inverted repeat lacking clade (IRLC), which contained 77 protein-coding genes, 29 tRNA genes, and four rRNA genes. The mitogenome was 378,373 bp long and encoded 54 unique genes, including 33 protein-coding, three ribosomal RNA (rRNA), and 18 transfer RNA (tRNA) genes. In addition to the single circular conformation, alternative conformations mediated by one and four repetitive sequences in the plastome and mitogenome were identified and validated, respectively. The inverted repeat (PDR12, the 12th dispersed repeat sequence in C. spinosa plastome) of plastome mediating recombinant was conserved in the genus Caragana. Furthermore, we identified 14 homologous fragments by comparing the sequences of mitogenome and plastome, including eight complete tRNA genes. A phylogenetic analysis of protein-coding genes extracted from the plastid and mitochondrial genomes revealed congruent topologies. Analyses of sequence divergence found one intergenic region, trnN-GUU-ycf1, exhibiting a high degree of variation, which can be used to develop novel molecular markers to distinguish the nine Caragana species accurately. This plastome and mitogenome of C. spinosa could provide critical information for the molecular breeding of C. spinosa and be used as a reference genome for other species of Caragana. In this study, we assembled the complete plastome and mitogenome of Caragana spinosa and explored the multiple configurations of the organelle genomes.

Lectotypification and nomenclature notes of the name Caraganaopulens (Fabaceae, Papilionoideae) and its synonyms

Morphological characters currently used to differentiate Caraganaopulens as a species have been found to be insufficient and inconsistent. Through extensive research and comparisons of specimens, it has been revealed that C.opulens and its synonyms have overlapping geographical distributions, and that typification is necessary for C.opulens. Therefore, a lectotype is designated for the name C.opulens, with comments on its typification. Additionally, the current typification status is discussed for all its synonyms, accompanied by substantive notes.

Nuclear phylotranscriptomics and phylogenomics support numerous polyploidization events and hypotheses for the evolution of rhizobial nitrogen-fixing symbiosis in Fabaceae

Fabaceae are the third largest angiosperm family, with 765 genera and ∼19 500 species. They are important both economically and ecologically, and global Fabaceae crops are intensively studied in part for their nitrogen-fixing ability. However, resolution of the intrasubfamilial Fabaceae phylogeny and divergence times has remained elusive, precluding a reconstruction of the evolutionary history of symbiotic nitrogen fixation in Fabaceae. Here, we report a highly resolved phylogeny using >1500 nuclear genes from newly sequenced transcriptomes and genomes of 391 species, along with other datasets, for a total of 463 legumes spanning all 6 subfamilies and 333 of 765 genera. The subfamilies are maximally supported as monophyletic. The clade comprising subfamilies Cercidoideae and Detarioideae is sister to the remaining legumes, and Duparquetioideae and Dialioideae are successive sisters to the clade of Papilionoideae and Caesalpinioideae. Molecular clock estimation revealed an early radiation of subfamilies near the K/Pg boundary, marked by mass extinction, and subsequent divergence of most tribe-level clades within ∼15 million years. Phylogenomic analyses of thousands of gene families support 28 proposed putative whole-genome duplication/whole-genome triplication events across Fabaceae, including those at the ancestors of Fabaceae and five of the subfamilies, and further analyses supported the Fabaceae ancestral polyploidy. The evolution of rhizobial nitrogen-fixing nodulation in Fabaceae was probed by ancestral character reconstruction and phylogenetic analyses of related gene families and the results support the hypotheses of one or two switch(es) to rhizobial nodulation followed by multiple losses. Collectively, these results provide a foundation for further morphological and functional evolutionary analyses across Fabaceae.

Prospects for the use of Caragana fruits (Caragana arborescens and C. frutex) as alternative raw materials for the food industry

Currently, there is an increase in the world’s population against the background of a reduction in land suitable for growing traditional agricultural crops. This is especially true for Asian countries. Due to a number of factors, the areas of fertile land are decreasing, and the areas of saline land are increasing; arid areas of the planet are expanding. In this regard, it is important to introduce plants into the culture that can grow on poor, arid, saline soils. The purpose of the research is to study vegetable raw materials from fruits Caragana arborescens and C. frutex, undergoing introduction tests in the arboretum of the Tsytsin Main Botanical Garden of Russian Academy of Sciences, to find out the possibilities and advantages of their use in the food industry in a comparative aspect. A comparative assessment of the size and weight characteristics of the fruits and seeds of C. arborescens and C. frutex studied by us indicates the possibilities of their industrial food use in the future, along with a good introduction, and, probably, plantation potential of these plants.

Combined high leaf hydraulic safety and efficiency provides drought tolerance in Caragana species adapted to low mean annual precipitation

Clarifying the coordination of leaf hydraulic traits with gas exchange across closely-related species adapted to varying rainfall can provide insights into plant habitat distribution and drought adaptation. The leaf hydraulic conductance (K_leaf ), stomatal conductance (g_s ), net assimilation (A), vein embolism and abscisic acid (ABA) concentration during dehydration were quantified, as well as pressure-volume curve traits and vein anatomy in 10 Caragana species adapted to a range of mean annual precipitation (MAP) conditions and growing in a common garden. We found a positive correlation between Ψ_leaf at 50% loss of K_leaf (K_leaf P₅₀ ) and maximum K_leaf (K_leaf-max ) across species. Species from low-MAP environments exhibited more negative K_leaf P₅₀ and turgor loss point, and higher K_leaf-max and leaf-specific capacity at full turgor, along with higher vein density and midrib xylem per leaf area, and a higher ratio of K_leaf-max : maximum g_s . Tighter stomatal control mediated by higher ABA accumulation during dehydration in these species resulted in an increase in hydraulic safety and intrinsic water use efficiency (WUE_i ) during drought. Our results suggest that high hydraulic safety and efficiency combined with greater stomatal sensitivity triggered by ABA production and leading to greater WUE_i provides drought tolerance in Caragana species adapted to low-MAP environments.

Precipitation is the main factor affecting the variation of foliar nitrogen isotope composition in two leguminous shrub species of northwestern China

An increase in foliar nitrogen isotope composition (δ15N) with decreasing precipitation has been shown to occur widely in non-N2-fixing plant species. However, similar patterns have not been identified in N2-fixing species. Here, we tested the relationships of foliar δ15N with local environmental factors and leaf properties in two leguminous shrub species (Caragana korshinskii and Caragana liouana) sampled from 30 populations. Results indicated that the mean annual precipitation (MAP) primarily accounted for the variation of foliar δ15N in the two species. Further analysis revealed strong negative correlations between foliar δ15N and MAP within and across species. These results suggest that the foliar δ15N of leguminous shrub species also shift along precipitation gradients, which augments our understanding of the relationships between foliar δ15N and climatic factors.

Variations of Bacterial Community Diversity Within the Rhizosphere of Three Phylogenetically Related Perennial Shrub Plant Species Across Environmental Gradients

Rhizosphere microbial communities are of great importance to mediate global biogeochemical cycles, plant growth, and fitness. Yet, the processes that drive their assembly remain unclear. The perennial shrubs Caragana spp., which is well known for their role in soil and water conservation, provides an ideal system to study the biogeography of rhizosphere microorganism communities within natural ecosystems. In order to detect how bacterial rhizosphere communities vary in terms of community diversity and composition, the rhizosphere bacterial community of three Caragana species, Caragana microphylla Lam., C. liouana Zhao, and C. korshinskii Kom., which distributed in arid and semi-arid region of northern China were investigated. Across species, Proteobacteria (61.1%), Actinobacteria (16.0%), Firmicutes (8.6%), Bacteroidetes (3.0%), Acidobacteria (3.5%), Gemmatimonadetes (1.4%), and Cyanobacteria (1.0%) were the most dominant phyla in the rhizosphere of the three Caragana species. The relative abundance of Cyanobacteria was significantly higher in rhizosphere of C. korshinskii Kom. compared with C. microphylla Lam. and C. liouana Zhao, while the opposite was found for Gemmatimonadetes in rhizosphere of C. microphylla Lam. relative to C. liouana Zhao. Stepwise multiple linear regression analysis showed that both diversity and richness of the bacterial rhizosphere communities significantly and positively correlated with soil pH (p < 0.01). Distance-based redundancy analysis indicated that soil properties and non-soil parameters detected there accounted for 47.5% of bacterial phylogenetic structure variation (p < 0.01) all together. Meanwhile, soil total phosphorus accounted for the greatest proportion of community structure variance (9.7%, p < 0.01), followed by electrical conduction (6.5%), altitude (5.8%), soil pH (5.4%), mean annual precipitation (3.6%) and total nitrogen (3.6%, p < 0.05 in all cases). Furthermore, partial Mantel test suggested that bacterial rhizosphere community structure significantly correlated with geographical distance, indicating that the less geographical distant sample sites tend to harbor more similar bacterial rhizosphere community. Our results shed new light on the mechanisms of coevolution and interaction between long-lived plants and their rhizosphere bacterial communities across environmental gradients.

DNA barcoding of vouchered xylarium wood specimens of nine endangered Dalbergia species

ITS2+ trnH - psbA was the best combination of DNA barcode to resolve the Dalbergia wood species studied. We demonstrate the feasibility of building a DNA barcode reference database using xylarium wood specimens. The increase in illegal logging and timber trade of CITES-listed tropical species necessitates the development of unambiguous identification methods at the species level. For these methods to be fully functional and deployable for law enforcement, they must work using wood or wood products. DNA barcoding of wood has been promoted as a promising tool for species identification; however, the main barrier to extensive application of DNA barcoding to wood is the lack of a comprehensive and reliable DNA reference library of barcodes from wood. In this study, xylarium wood specimens of nine Dalbergia species were selected from the Wood Collection of the Chinese Academy of Forestry and DNA was then extracted from them for further PCR amplification of eight potential DNA barcode sequences (ITS2, matK, trnL, trnH-psbA, trnV-trnM1, trnV-trnM2, trnC-petN, and trnS-trnG). The barcodes were tested singly and in combination for species-level discrimination ability by tree-based [neighbor-joining (NJ)] and distance-based (TaxonDNA) methods. We found that the discrimination ability of DNA barcodes in combination was higher than any single DNA marker among the Dalbergia species studied, with the best two-marker combination of ITS2+trnH-psbA analyzed with NJ trees performing the best (100% accuracy). These barcodes are relatively short regions (<350 bp) and amplification reactions were performed with high success (≥90%) using wood as the source material, a necessary factor to apply DNA barcoding to timber trade. The present results demonstrate the feasibility of using vouchered xylarium specimens to build DNA barcoding reference databases.

Seed germination of Caragana species from different regions is strongly driven by environmental cues and not phylogenetic signals

Seed germination behavior is an important factor in the distribution of species. Many studies have shown that germination is controlled by phylogenetic constraints, however, it is not clear whether phylogenetic constraints or environmental cues explain seed germination of a genus from a common ancestor. In this study, seed germination under different temperature- and water-regimes [induced by different osmotic potentials of polyethylene glycol (PEG)] was investigated in the phylogenetically-related Caragana species that thrive in arid, semiarid, semihumid and humid environments. The results showed that the final percentage germination (FPG) decreased from 95% in species from arid habitats to 0% in species from humid habitats, but with no significant phylogenetic signal. Rather, the response of seed germination to temperature and PEG varied greatly with species from arid to humid habitats and was tightly linked to the ecological niche of the species, their seed coat structure and abscisic acid concentration. The findings are not consistent with the hypothesis that within a family or a genus, seed germination strategies can be a stable evolutionary trait, thus constraining interspecific variation, but the results clearly show that seed germination of Caragana species distributed across a range of habitats has adapted to the environment of that habitat.

Himalayan uplift shaped biomes in Miocene temperate Asia: evidence from leguminous Caragana

Caragana, with distinctive variation in leaf and rachis characters, exhibits three centers of geographic distribution, i.e., Central Asia, the Qinghai-Tibetan Plateau (QTP), and East Asia, corresponding to distinct biomes. Because Caragana species are often ecologically dominant components of the vegetation in these regions, it is regarded as a key taxon for the study of floristic evolution in the dry regions of temperate Asia. Based on an expanded data set of taxa and gene regions from those previously generated, we employed molecular clock and biogeographical analyses to infer the evolutionary history of Caragana and link it to floristic patterns, paleovegetation, and paleoclimate. Results indicate that Caragana is of arid origin from the Junggar steppe. Diversification of crown group Caragana, dated to the early Miocene ca. 18 Ma and onwards, can be linked to the Himalayan Motion stage of QTP uplift. Diversification of the major clades in the genus corresponding to taxonomic sections and morphological variation is inferred to have been driven by the uplift, as well as Asian interior aridification and East Asian monsoon formation, in the middle to late Miocene ca. 12~6 Ma. These findings demonstrate a synchronous evolution among floristics, vegetation and climate change in arid Central Asia, cold arid alpine QTP, and mesophytic East Asia.

Drought responses of three closely related Caragana species: implication for their vicarious distribution

Drought is a major environmental constraint affecting growth and distribution of plants in the desert region of the Inner Mongolia plateau. Caragana microphylla, C. liouana, and C. korshinskii are phylogenetically close but distribute vicariously in Mongolia plateau. To gain a better understanding of the ecological differentiation between these three species, we examined the leaf gas exchange, growth, water use efficiency, biomass accumulation and allocation by subjecting their seedlings to low and high drought treatments in a glasshouse. Increasing drought stress had a significant effect on many aspects of seedling performance in all species, but the physiology and growth varied with species in response to drought. C. korshinskii exhibited lower sensitivity of photosynthetic rate and growth, lower specific leaf area, higher biomass allocation to roots, higher levels of water use efficiency to drought compared with the other two species. Only minor interspecific differences in growth performances were observed between C. liouana and C. microphylla. These results indicated that faster seedling growth rate and more efficient water use of C. korshinskii should confer increased drought tolerance and facilitate its establishment in more severe drought regions relative to C. liouana and C. microphylla.

A molecular phylogeny of Caraganeae (Leguminosae, Papilionoideae) reveals insights into new generic and infrageneric delimitations

Based on sequence data of nuclear ITS and plastid matK, trnL-F and psbA-trnH markers, the phylogeny of the subtribes Caraganinae and Chesneyinae in tribe Caraganeae was inferred. The results support the monophyly of each of the subtribes. Within subtribes Caraganinae, Calophaca and Halimodendron are herein transferred into Caragana to ensure its generic monophyly. The subtribe Chesneyinae is composed of four well-supported genera: Chesneya, Chesniella, Gueldenstaedtia and Tibetia. Based on phylogenetic, morphological, distributional and habitat type evidence, the genus Chesneya was divided into three monophyletic sections: Chesneya sect. Chesneya, Chesneya sect. Pulvinatae and Chesneya sect. Spinosae. Chesneya macrantha is herein transferred into Chesniella. Spongiocarpella is polyphyletic and its generic rank is not maintained. The position of Chesneya was incongruent in the nuclear ITS and the plastid trees. A paternal chloroplast capture event via introgression is hypothesized for the origin of Chesneya, which is postulated to have involved the common ancestor of Chesniella (♂) and that of the Gueldenstaedtia - Tibetia (GUT) clade (♀) as the parents.

Spatiotemporal evolution of Calophaca (fabaceae) reveals multiple dispersals in central Asian mountains

BACKGROUND

The Central Asian flora plays a significant role in Eurasia and the Northern Hemisphere. Calophaca, a member of this flora, includes eight currently recognized species, and is centered in Central Asia, with some taxa extending into adjacent areas. A phylogenetic analysis of the genus utilizing nuclear ribosomal ITS and plastid trnS-trnG and rbcL sequences was carried out in order to confirm its taxonomic status and reconstruct its evolutionary history.

METHODOLOGY/PRINCIPAL FINDING

We employed BEAST Bayesian inference for dating, and S-DIVA and BBM for ancestral area reconstruction, to study its spatiotemporal evolution. Our results show that Calophacais monophyletic and nested within Caragana. The divergence time of Calophaca is estimated at ca. 8.0 Ma, most likely driven by global cooling and aridification, influenced by rapid uplift of the Qinghai Tibet Plateau margins.

CONCLUSIONS/SIGNIFICANCE

According to ancestral area reconstructions, the genus most likely originated in the Pamir Mountains, a global biodiversity hotspot and hypothesized Tertiary refugium of many Central Asian plant lineages. Dispersals from this location are inferred to the western Tianshan Mountains, then northward to the Tarbagatai Range, eastward to East Asia, and westward to the Caucasus, Russia, and Europe. The spatiotemporal evolution of Calophaca provides a case contributing to an understanding of the flora and biodiversity of the Central Asian mountains and adjacent regions.

De novo assembly of transcriptome sequencing in Caragana korshinskii Kom. and characterization of EST-SSR markers

Caragana korshinskii Kom. is widely distributed in various habitats, including gravel desert, clay desert, fixed and semi-fixed sand, and saline land in the Asian and African deserts. To date, no previous genomic information or EST-SSR marker has been reported in Caragana Fabr. genus. In this study, more than two billion bases of high-quality sequence of C. korshinskii were generated by using illumina sequencing technology and demonstrated the de novo assembly and annotation of genes without prior genome information. These reads were assembled into 86,265 unigenes (mean length = 709 bp). The similarity search indicated that 33,955 and 21,978 unigenes showed significant similarities to known proteins from NCBI non-redundant and Swissprot protein databases, respectively. Among these annotated unigenes, 26,232 a unigenes were separately assigned to Gene Ontology (GO) database. When 22,756 unigenes searched against the Kyoto Encyclopedia of Genes and Genomes Pathway (KEGG) database, 5,598 unigenes were assigned to 5 main categories including 32 KEGG pathways. Among the main KEGG categories, metabolism was the biggest category (2,862, 43.7%), suggesting the active metabolic processes in the desert tree. In addition, a total of 19,150 EST-SSRs were identified from 15,484 unigenes, and the characterizations of EST-SSRs were further compared with other four species in Fabraceae. 126 potential marker sites were randomly selected to validate the assembly quality and develop EST-SSR markers. Among the 9 germplasms in Caranaga Fabr. genus, PCR success rate were 93.7% and the phylogenic tree was constructed based on the genotypic data. This research generated a substantial fraction of transcriptome sequences, which were very useful resources for gene annotation and discovery, molecular markers development, genome assembly and annotation. The EST-SSR markers identified and developed in this study will facilitate marker-assisted selection breeding.

Himalayan origin and evolution of Myricaria (Tamaricaeae) in the neogene

Background

Myricaria consists of about twelve-thirteen species and occurs in Eurasian North Temperate zone, most species in the Qinghai-Tibet Plateau (QTP) and adjacent areas.

Methodology/Principal Findings

Twelve species of Myricaria plus two other genera Tamarix and Reaumuria in Tamaricaceae, were sampled, and four markers, ITS, rps16, psbB-psbH, and trnL-trnF were sequenced. The relaxed Bayesian molecular clock BEAST method was used to perform phylogenetic analysis and molecular dating, and Diva, S-Diva, and maximum likelihood Lagrange were used to estimate the ancestral area. The results indicated that Myricaria could be divided into four phylogenetic clades, which correspond to four sections within the genus, of them two are newly described in this paper. The crown age of Myricaria was dated to early Miocene ca. 20 Ma, at the probable early uplifting time of the Himalayas. The Himalayas were also shown as the center of origin for Myricaria from the optimization of ancestral distribution. Migration and dispersal of Myricaria were indicated to have taken place along the Asian Mountains, including the Himalayas, Kunlun, Altun, Hendukosh, Tianshan, Altai, and Caucasus etc., westward to Europe, eastward to Central China, and northward to the Mongolian Plateau.

Conclusions/Significance

Myricaria spatiotemporal evolution presented here, especially the Himalayan origin at early Miocene ca. 20 Ma, and then migrated westward and eastward along the Asian mountains, offers a significant evolutionary case for QTP and Central Asian biogeography.

Phenolic compounds from Halimodendron halodendron (Pall.) voss and their antimicrobial and antioxidant activities

Halimodendron halodendron has been used as forage in northwestern China for a long time. Its young leaves and flowers are edible and favored by indigenous people. In this study, eleven phenolic compounds were bioassay-guided and isolated from the aerial parts of H. halodendron for the first time. They were identified by means of physicochemical and spectrometric analysis as quercetin (1), 3,5,7,8,4′-pentahydroxy-3′-methoxy flavone (2), 3-O-methylquercetin (3), 3,3′-di-O-methylquercetin (4), 3,3′-di-O-methylquercetin-7-O-β-d-glucopyranoside (5), isorhamentin-3-O-β-d-rutinoside (6), 8-O-methylretusin (7), 8-O-methylretusin-7-O-β-d-glucopyranoside (8), salicylic acid (9), p-hydroxybenzoic acid (ferulic acid) (10), and 4-hydroxy-3-methoxy cinnamic acid (11). They were sorted as flavonols (1–6), soflavones (7 and 8), and phenolic acids (9–11). Among the compounds, flanools 1–4 revealed a strong antibacterial activity with minimum inhibitory concentration (MIC) values of 50–150 μg/mL, and median inhibitory concentration (IC₅₀) values of 26.8–125.1 μg/mL. The two isoflavones (7 and 8) showed moderate inhibitory activity on the test bacteria. Three phenolic acids (9, 10 and 11) showed strong antibacterial activity with IC₅₀ values of 28.1–149.7 μg/mL. Antifungal activities of the compounds were similar to their antibacterial activities. All these phenolic compounds showed significant antimicrobial activity with a broad spectrum as well as antioxidant activity based on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and β-carotene-linoleic acid bleaching assays. In general, the flavonol aglycones with relatively low polarity exhibited stronger activities than the glycosides. The results suggest the potential of this plant as a source of functional food ingredients and provide support data for its utilization as forage as well.

Antimicrobial and Antioxidant Activities of the Flower Essential Oil of Halimodendron halodendron

The essential oil obtained by hydrodistillation from the flowers of Halimondendron halodendron (Leguminosae) was analyzed for its chemical composition by gas chromatography-mass spectrometry (GC-MS). Undecane (16.4%), dodecane (15.3%), tridecane (12.5%), decane (8.2%), 6,10,14-trimethyl-pentadecan-2-one (6.3%), methyl palmitate (6.0%), methyl linolenate (4.1%) and ethylcyclohexane (4.1%) were the major compounds of the thirty-five identified components of the oil. The essential oil was shown to have a broad spectrum of antimicrobial activity with MIC values ranging from 100 to 250 μg/mL, and IC50 values from 40.4 to 193.8 μg/mL. The oil also showed strong antioxidant activity, with an especially high metal chelating capacity of ferrous ions with an IC50 value of 7.4 μg/mL on ferrozine-Fe2+ complex formation.

Preparative separation of phenolic compounds from Halimodendron halodendron by high-speed counter-current chromatography

Three phenolic compounds, p-hydroxybenzoic acid (1), isorhamnetin-3-O-β-D-rutinoside (2), and 3,3′-di-O-methylquercetin (5), along with a phenolic mixture were successfully separated from the ethyl acetate crude extract of Halimodendron halodendron by high-speed counter-current chromatography (HSCCC) with chloroform-methanol-water-acetic acid (4:3:2:0.05, v/v) as the two-phase solvent system. The phenolic mixture from HSCCC was further separated by preparative HPLC and purified by Sephadex LH-20 to afford quercetin (3) and 3-O-methylquercetin (4). Seven hundred mg of ethyl acetate crude extract was separated by HSCCC to obtain six fractions which were then analyzed by high performance liquid chromatography (HPLC). The HSCCC separation obtained total of 80 mg of the mixture of quercetin (3) and 3-O-methylquercetin (4) (26.43% and 71.89%, respectively) in fraction 2, 14 mg of 3,3′-di-O-methylquercetin (5) at 95.14% of purity in fraction 3, 15 mg of p-hydroxybenzoic acid (1) at 92.83% of purity in fraction 5, 12 mg of isorhamnetin-3-O-β-D-rutinoside (2) at 97.99% of purity in fraction 6. This is the first time these phenolic compounds have been obtained from H. halodendron, and their chemical structures identified by means of physicochemical and spectrometric analysis.