Identification of shikonin and its ester derivatives from the roots of Echium italicum L

Pharmacological Significance of Boraginaceae with Special Insights into Shikonin and Its Potential in the Food Industry

Shikonin is a naphthoquinone pigment present in the hairy roots of the plant species from the Boraginaceae family. The compound has been well investigated for its highly efficient medicinal, antioxidant, and antimicrobial properties. Various extraction methodologies have been employed to maximise yield while minimising waste production of shikonin and its derivatives. Despite substantial research on shikonin and Boraginaceae plants, a research gap persists in the food industry and extraction technologies. This review addresses crucial aspects of shikonin deserving of further exploration. It begins by elucidating the attributes of the Boraginaceae plants and their medicinal traits in folklore. It proceeds to focus on the roots of the plant and its medicinal properties, followed by extraction procedures explored in the last fifteen years, emphasising the novel technologies that have been chosen to improve the yield extract while minimising extraction times. Furthermore, this review briefly outlines studies employing cell culture techniques to enhance in vitro shikonin production. Lastly, attention is directed towards research in the food industry, particularly on shikonin-loaded biodegradable films and the antioxidant activity of shikonin. This review concludes by summarising the future potential in food science and prominent research gaps in this field.

Comparative Analysis of Shikonin and Alkannin Acyltransferases Reveals Their Functional Conservation in Boraginaceae

Shikonin and its enantiomer, alkannin, are bioactive naphthoquinones produced in several plants of the family Boraginaceae. The structures of these acylated derivatives, which have various short-chain acyl moieties, differ among plant species. The acylation of shikonin and alkannin in Lithospermum erythrorhizon was previously reported to be catalyzed by two enantioselective BAHD acyltransferases, shikonin O-acyltransferase (LeSAT1) and alkannin O-acyltransferase (LeAAT1). However, the mechanisms by which various shikonin and alkannin derivatives are produced in Boraginaceae plants remain to be determined. In the present study, evaluation of six Boraginaceae plants identified 23 homologs of LeSAT1 and LeAAT1, with 15 of these enzymes found to catalyze the acylation of shikonin or alkannin, utilizing acetyl-CoA, isobutyryl-CoA or isovaleryl-CoA as an acyl donor. Analyses of substrate specificities of these enzymes for both acyl donors and acyl acceptors and determination of their subcellular localization using Nicotiana benthamiana revealed a distinct functional differentiation of BAHD acyltransferases in Boraginaceae plants. Gene expression of these acyltransferases correlated with the enantiomeric ratio of produced shikonin/alkannin derivatives in L. erythrorhizon and Echium plantagineum. These enzymes showed conserved substrate specificities for acyl donors among plant species, indicating that the diversity in acyl moieties of shikonin/alkannin derivatives involved factors other than the differentiation of acyltransferases. These findings provide insight into the chemical diversification and evolutionary processes of shikonin/alkannin derivatives.

Natural products derived from medicinal plants and microbes might act as a game-changer in breast cancer: a comprehensive review of preclinical and clinical studies

Breast cancer (BC) is the most prevalent neoplasm among women. Genetic and environmental factors lead to BC development and on this basis, several preventive - screening and therapeutic interventions have been developed. Hormones, both in the form of endogenous hormonal signaling or hormonal contraceptives, play an important role in BC pathogenesis and progression. On top of these, breast microbiota includes both species with an immunomodulatory activity enhancing the host's response against cancer cells and species producing proinflammatory cytokines associated with BC development. Identification of novel multitargeted therapeutic agents with poly-pharmacological potential is a dire need to combat advanced and metastatic BC. A growing body of research has emphasized the potential of natural compounds derived from medicinal plants and microbial species as complementary BC treatment regimens, including dietary supplements and probiotics. In particular, extracts from plants such as Artemisia monosperma Delile, Origanum dayi Post, Urtica membranacea Poir. ex Savigny, Krameria lappacea (Dombey) Burdet & B.B. Simpson and metabolites extracted from microbes such as Deinococcus radiodurans and Streptomycetes strains as well as probiotics like Bacillus coagulans and Lactobacillus brevis MK05 have exhibited antitumor effects in the form of antiproliferative and cytotoxic activity, increase in tumors' chemosensitivity, antioxidant activity and modulation of BC - associated molecular pathways. Further, bioactive compounds like 3,3'-diindolylmethane, epigallocatechin gallate, genistein, rutin, resveratrol, lycopene, sulforaphane, silibinin, rosmarinic acid, and shikonin are of special interest for the researchers and clinicians because these natural agents have multimodal action and act via multiple ways in managing the BC and most of these agents are regularly available in our food and fruit diets. Evidence from clinical trials suggests that such products had major potential in enhancing the effectiveness of conventional antitumor agents and decreasing their side effects. We here provide a comprehensive review of the therapeutic effects and mechanistic underpinnings of medicinal plants and microbial metabolites in BC management. The future perspectives on the translation of these findings to the personalized treatment of BC are provided and discussed.

Phytochemical Profiling and Biological Potential of Prunus dulcis Shell Extracts

Prunus dulcis is one of the most widely cultivated species in the world. Its fruit (almond) is rich in various nutritious and bioactive compounds that exert several beneficial effects. The aim of this study was to determine the chemical profile and evaluate the biological potential in vitro of almond shell extracts. The chemical analysis of shell extracts led to the identification of 15 compounds by HPLC-DAD, of which 11 were first detected in the almond plant. Twenty-six volatile compounds were identified by the GC-MS technique; among them, seven were firstly detected in the studied plant. For the biological activities, the extracts demonstrated moderate inhibition potential against the antioxidant, antidiabetic, and cytotoxic activities. The methanol extract at 50 µg/mL showed the highest antioxidant (45%) and antidiabetic activities (45% against alpha-glucosidase and 31% against alpha-amylase extracts), while the cyclohexane and dichloromethane at 50 µg/mL showed the highest cytotoxic activity towards Hela (32.2% with cyclohexane) and RAW 264-7 (45% with dichloromethane). Overall, these findings demonstrate the potential of almond shell extracts as a source of bioactive compounds that could be applied in the pharmaceutical and medical fields.

Genome-Wide Identification of LeBAHDs in Lithospermum erythrorhizon and In Vivo Transgenic Studies Confirm the Critical Roles of LeBAHD1/LeSAT1 in the Conversion of Shikonin to Acetylshikonin

The BAHD acyltransferase family is a unique class of plant proteins that acylates plant metabolites and participates in plant secondary metabolic processes. However, the BAHD members in Lithospermum erythrorhizon remain unknown and uncharacterized. Although the heterologously expressed L. erythrorhizon BAHD family member LeSAT1 in Escherichia coli has been shown to catalyze the conversion of shikonin to acetylshikonin in vitro, its in vivo role remains unknown. In this study, the characterization, evolution, expression patterns, and gene function of LeBAHDs in L. erythrorhizon were explored by bioinformatics and transgenic analysis. We totally identified 73 LeBAHDs in the reference genome of L. erythrorhizon. All LeBAHDs were phylogenetically classified into five clades likely to perform different functions, and were mainly expanded by dispersed and WGD/segmental duplication. The in vivo functional investigation of the key member LeBAHD1/LeSAT1 revealed that overexpression of LeBAHD1 in hairy roots significantly increased the content of acetylshikonin as well as the conversion rate of shikonin to acetylshikonin, whereas the CRISPR/Cas9-based knockout of LeBAHD1 in hairy roots displayed the opposite trend. Our results not only confirm the in vivo function of LeBAHD1/LeSAT1 in the biosynthesis of acetylshikonin, but also provide new insights for the biosynthetic pathway of shikonin and its derivatives.

Naphthoquinones and triterpenoids from Arnebia euchroma (Royle) Johnst and their hypoglycemic and lipid-lowering effects

A new pentacyclic triterpenoid, 2-hydroxy-1-ene-hydroxyhopanone (19), and a new benzoxepin-5-one, 3-(4-methyl-3-penten-1-yl)-6-hydroxy-9-methoxy-2H-1-benzoxepin-5-one (25), along with 26 known compounds (1-18, 20-24, 26-28), were isolated from the roots of Arnebia euchroma (Royle) Johnst. The structures of the new compounds were elucidated by extensive spectroscopic analyses. The absolute configurations of shikonofurans 9-13 were determined by quantum chemical ECD calculations and CD spectra comparison for the first time. Pharmacological study revealed that naphthoquinones 1-5, 7, and 8 had obvious cytotoxicity toward human lung adenocarcinoma A549 cell line. Meanwhile, the hypoglycemic and lipid-lowering effects of isolated compounds were assessed by checking their inhibitory effects on key enzymes regulating glucose and lipid metabolism. Results showed that compounds 1, 3, 5, 6, 8, 18, and 19 could inhibit the activity of ATP-citrate lyase (ACL); compound 7 could inhibit the activity of acetyl-CoA carboxylase (ACC1); while compounds 8 and 19 showed inhibitory effects on protein tyrosine phosphatase 1B (PTP1B). Among them, the naphthoquinone 6, steroid 18, and triterpenoid 19 showed moderate inhibitory effects on ACL and PTP1B, but didn't exhibit obvious cytotoxicity. This study demonstrated that compounds 6, 18, and 19 show great promising for the development of new agents for the treatment of metabolic diseases.

Discrimination of Zicao Samples Based on DNA Barcoding and HPTLC Fingerprints, and Identification of (22E)-Ergosta-4,6,8(14),22-tetraen-3-one As a Marker Compound

The unambiguous identification of plant material is a prerequisite of rational phytotherapy. Misidentification can even cause serious health problems, as in the case of the Chinese medicinal herb Zicao. Commercial material labelled "Zicao" may be derived from the roots of Arnebia euchroma (ruan zicao), Lithospermum erythrorhizon (ying zicao), or Onosma paniculata (dian zicao). All of these roots contain shikonin derivatives as main bioactive constituents, but ying zicao and dian zicao contain also hepatotoxic pyrrolizidine alkaloids in high amounts. Therefore, the use of A. euchroma with a very low pyrrolizidine alkaloid content is desirable. Confusions of the species occur quite often, indicating an urgent need for an unambiguous identification method. Discrimination of 23 zicao samples has been achieved by analyses of the nuclear internal transcribed spacer ITS2 and trnL-F intergenic spacer of the chloroplast DNA. Data were analyzed using Bioedit, ClustalX, Mega 11 and BLAST. Results indicate that ITS2 barcoding can accurately distinguish Arnebia euchroma from their adulterants. Subsequently, an HPTLC method has been developed allowing a chemical discrimination of the most widely used species. (22E)-Ergosta-4,6,8(14),22-tetraen-3-one has been identified as characteristic marker compound, allowing an unambiguous discrimination of A. euchroma and L. erythrorhizon.

Evaluation of herb-drug interaction of ambrisentan with shikonin based on UPLC-MS/MS

CONTEXT

Ambrisentan is an oral endothelin-receptor antagonist (ERA). However, there is no report on the interaction between ambrisentan and shikonin.

OBJECTIVE

To investigate the effect of shikonin on ambrisentan metabolism in vivo and in vitro.

MATERIALS AND METHODS

This study developed an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for simultaneous determination of ambrisentan and (S)-4-hydroxymethyl ambrisentan in rat plasma. Twelve male Sprague-Dawley (SD) rats were divided into two groups (n = 6): the control group and shikonin (20 mg/kg) group. The pharmacokinetics of ambrisentan (2.5 mg/kg) were investigated after 30 min. Additionally, human and rat liver microsomes were used to investigate the herb-drug interaction.

RESULTS

The UPLC-MS/MS method was shown to be accurate, precise and reliable, and was successfully applied to the herb-drug interaction study of ambrisentan with shikonin. When co-administrated with 20 mg/kg shikonin, the C_max and AUC_(0-∞) of ambrisentan were significantly increased by 44.96 and 16.65%, respectively (p < 0.05). In addition, there were modest decreases in (S)-4-hydroxymethyl ambrisentan C_max and AUC_(0-∞) in the presence of shikonin (p < 0.05), which indicated that these results were in accordance with the inhibition of shikonin on ambrisentan metabolism. Moreover, enzyme kinetic study indicated that shikonin had an inhibitory effect on human and rat microsomes where the IC₅₀ values of shikonin were 5.865 and 6.358 μM, respectively.

CONCLUSIONS

Our study indicated that shikonin could inhibit ambrisentan metabolism. Further studies need to be carried out to verify whether similar interaction truly apply in humans and whether this interaction has clinical significance.

Synthesis and Pharmacological In Vitro Investigations of Novel Shikonin Derivatives with a Special Focus on Cyclopropane Bearing Derivatives

Melanoma is the deadliest form of skin cancer and accounts for about three quarters of all skin cancer deaths. Especially at an advanced stage, its treatment is challenging, and survival rates are very low. In previous studies, we showed that the constituents of the roots of Onosma paniculata as well as a synthetic derivative of the most active constituent showed promising results in metastatic melanoma cell lines. In the current study, we address the question whether we can generate further derivatives with optimized activity by synthesis. Therefore, we prepared 31, mainly novel shikonin derivatives and screened them in different melanoma cell lines (WM9, WM164, and MUG-Mel2 cells) using the XTT viability assay. We identified (R)-1-(1,4-dihydro-5,8-dihydroxy-1,4-dioxonaphthalen-2-yl)-4-methylpent-3-enyl 2-cyclopropyl-2-oxoacetate as a novel derivative with even higher activity. Furthermore, pharmacological investigations including the ApoToxGlo^TM Triplex assay, LDH assay, and cell cycle measurements revealed that this compound induced apoptosis and reduced cells in the G1 phase accompanied by an increase of cells in the G2/M phase. Moreover, it showed hardly any effects on the cell membrane integrity. However, it also exhibited cytotoxicity against non-tumorigenic cells. Nevertheless, in summary, we could show that shikonin derivatives might be promising drug leads in the treatment of melanoma.

Allelopathy: The Chemical Language of Plants

In Nature, the oldest method of communication between living systems is the chemical language. Plants, due to their lack of mobility, have developed the most sophisticated way of chemical communication. Despite that many examples involve this chemical communication process-allelopathy, there is still a lack of information about specific allelochemicals released into the environment, their purpose, as well as in-depth studies on the chemistry underground. These findings are critical to gain a better understanding of the role of these compounds and open up a wide range of possibilities and applications, especially in agriculture and phytomedicine. The most relevant aspects regarding the chemical language of plants, namely kind of allelochemicals, have been investigated, as well as their releasing mechanisms and their purpose will be described in this chapter.

Pharmacology, toxicity and pharmacokinetics of acetylshikonin: a review

CONTEXT

Acetylshikonin, a naphthoquinone derivative, is mainly extracted from some species of the family Boraginaceae, such as Lithospermum erythrorhizon Sieb. et Zucc., Arnebia euchroma (Royle) Johnst., and Arnebia guttata Bunge. As a bioactive compound, acetylshikonin has attracted much attention because of its broad pharmacological properties.

OBJECTIVE

This review provides a comprehensive summary of the pharmacology, toxicity, and pharmacokinetics of acetylshikonin focussing on its mechanisms on the basis of currently available literature.

METHODS

The information of acetylshikonin from 1977 to 2020 was collected using major databases including Elsevier, Scholar, PubMed, Springer, Web of Science, and CNKI. Acetylshikonin, pharmacology, toxicity, pharmacokinetics, and naphthoquinone derivative were used as key words.

RESULTS

According to emerging evidence, acetylshikonin exerts a wide spectrum of pharmacological effects such as anticancer, anti-inflammatory, lipid-regulatory, antidiabetic, antibacterial, antifungal, antioxidative, neuroprotective, and antiviral properties. However, only a few studies have reported the adverse effects of acetylshikonin, with respect to reproductive toxicity and genotoxicity. Pharmacokinetic studies demonstrate that acetylshikonin is associated with a wide distribution and poor absorption.

CONCLUSIONS

Although experimental data supports the beneficial effects of this compound, acetylshikonin cannot be considered as a therapy drug without further investigations, especially, on the toxicity and pharmacokinetics.

Establishment of the hairy root culture of Echium plantagineum L. and its shikonin production

Echium plantagineum L. (Boraginaceae) is an invasive species in Australia and contains medicinal shikonins in its roots. In this study, the hairy root lines of E. plantagineum were established using Agrobacterium rhizogenes strain ATCC15834 and confirmed by the amplification of the rolB gene. Results showed significant difference in shikonin production between the hairy root lines in the ¹/₂B5 and M9 media. The biomass of the lines in the ¹/₂B5 medium was fivefold of that in the M9 medium. However, the components of detected shikonins were similar in these two liquid media. By contrast, different accumulation profiles appeared in the hairy root lines. HPLC analysis revealed the presence of nine possible related compounds, including shikonins, and acetylshikonin was the most abundant shikonin derivative. The content of acetylshikonin in the ¹/₂B5 medium (36.25 mg/L on average) was twofold of that in the M9 medium. Our results showed that the hairy root cultures of E. plantagineum can be used in enhancing the production of potential pharmaceutical compounds, such as acetylshikonin.

An integrated data filtering and identification strategy for rapid profiling of chemical constituents, with Arnebiae Radix as an example

Profiling the chemical components of complicated herbal extracts using traditional analytical methods is time-consuming and laborious. In this study, an integrated data filtering and identification strategy was developed to efficiently identify the chemical constituents in Arnebiae Radix. The post-acquisition data processing steps with this strategy were as follows: (1) data acquisition by ultra-high performance liquid chromatography-quadrupole-Orbitrap high-resolution mass spectrometry (UPLC-Q-Orbitrap-MS); (2) background subtraction on the basis of the total ion chromatogram (TIC) to obtain the background-subtracted ion chromatogram; (3) construction of a diagnostic ion database based on the measured MS/MS fragment ions of reference standards and auxiliary diagnostic information according to literatures; (4) mass defect filtering (MDF) to filter the background-subtracted ion chromatogram; and (5) rapid structural identification in the MDF-processed ion chromatogram on the basis of the diagnostic ion database and further structural confirmation by analysing the retention time, fragment behaviour, and online databases (Chemspider, PubChem, and SciFinder). In this study, the herbal medicine Arnebiae Radix was used to illustrate this strategy. A total of 96 compounds were efficiently exposed and characterized from Arnebiae Radix samples obtained from 20 sources, and 13 of these compounds were confirmed by comparison with the reference standards. Thirty components with a low abundance, that remained undetected in the TIC, were identified in the MDF-processed ion chromatogram. Nine of these compounds had not been identified from Arnebiae Radix previously, and were tentatively screened as unknowns. The chemical components in traditional Chinese medicine preparations are considered to be the material basis for the effectiveness of this medical system, and are closely related to the pharmacological activities of the drugs. The pharmacodynamics of these drugs are known to be influenced by the synergistic effects of various components. Therefore, comprehensive profiling of the chemical compositions of herbal extracts is essential for systematic elucidation of the pharmacodynamics of these medicines.

Antioxidant Properties and Reported Ethnomedicinal Use of the Genus Echium (Boraginaceae)

The genus Echium L. from the Boraginaceae family consists of 67 recognised species. The genus is widely distributed in the Mediterranean, having been documented in the traditional medicine of the area since 300 B.C. Current pharmacological studies have validated early ethnomedicinal properties showing that Echium spp. possesses antioxidant, analgesic, anxiolytic, anti-inflammatory, antibacterial, and antiviral effects. Nevertheless, only limited papers report specifically on the phytochemistry of this genus. Furthermore, the potential of utilising extracts from Echium species as natural antioxidant preparations has been significantly neglected. For the first time, this review comprehensively describes and discusses the presence of recorded Echium species with ethnomedicinal uses, their antioxidative properties in vitro and in vivo when available, and major phytochemical components recognised as potent antioxidants, as well as the possibilities and opportunities for future research.

A Simple Isocratic High-perfomance Liquid Chromatography Method for the Simultaneous Determination of Shikonin Derivatives in Some Echium Species Growing Wild in Turkey

Objectives

Dried roots of Echium species are used in Turkey for the treatment of wounds, inflammation, and depression. In this study, an reversed-phase-liquid chromatographic method with isocratic elution was developed to determine shikonin derivatives in Echium species.

Materials and Methods

The chromatographic separation and quantification was performed on a C18 column (ACE, 150 mm × 4.6 mm, 5 μm), with a mobile phase of acetonitrile and 0.1 M acetic acid (70: 30, v/v) at a flow rate of 1 mL/min, and ultraviolet detection at 520 nm.

Results

Linear behavior was observed over the investigated concentration range (2-500 ppm) for all analytes, with a correlation coefficient of >0.998. The proposed method was found to be specific and precise for the quantification of shikonin derivatives in Echium species.

Conclusion

The highest content of shikonin derivatives was observed in E. italicum L. compared with the other species studied herein, advocating the use of E. italicum L. roots as an alternate source for shikonin derivatives.

Involvement of LeMRP, an ATP-binding cassette transporter, in shikonin transport and biosynthesis in Lithospermum erythrorhizon

Shikonin and its derivatives are important medicinal secondary metabolites accumulating in roots of Lithospermum erythrorhizon. Although some membrane proteins have been identified as transporters of secondary metabolites, the mechanisms underlying shikonin transport and accumulation in L. erythrorhizon cells still remain largely unknown. In this study, we isolated a cDNA encoding LeMRP, an ATP-binding cassette transporter from L. erythrorhizon, and further investigated its functions in the transport and biosynthesis of shikonin using the yeast transformation and transgenic hairy root methods, respectively. Real-time PCR was applied for expression analyses of LeMRP and shikonin biosynthetic enzyme genes. Functional analysis of LeMRP using the heterologous yeast cell expression system showed that LeMRP could be involved in shikonin transport. Transgenic hairy roots of L. erythrorhizon demonstrated that LeMRP overexpressing hairy roots produced more shikonin than the empty vector (EV) control. Real-time PCR results revealed that the enhanced shikonin biosynthesis in the overexpression lines was mainly caused by highly up-regulated expression of genes coding key enzymes (LePAL, HMGR, Le4CL and LePGT) involved in shikonin biosynthesis. Conversely, LeMRP RNAi decreased the accumulation of shikonin and effectively down-regulated expression level of the above genes. Typical inhibitors of ABC proteins, such as azide and buthionine sulphoximine, dramatically inhibited accumulation of shikonin in hairy roots. Our findings provide evidence for the important direct or indirect role of LeMRP in transmembrane transport and biosynthesis of shikonin.

Involvement of LeMDR, an ATP-binding cassette protein gene, in shikonin transport and biosynthesis in Lithospermum erythrorhizon

BACKGROUND

Shikonin is a naphthoquinone secondary metabolite with important medicinal value and is found in Lithospermum erythrorhizon. Considering the limited knowledge on the membrane transport mechanism of shikonin, this study investigated such molecular mechanism.

RESULTS

We successfully isolated an ATP-binding cassette protein gene, LeMDR, from L. erythrorhizon. LeMDR is predominantly expressed in L. erythrorhizon roots, where shikonin accumulated. Functional analysis of LeMDR by using the yeast cell expression system revealed that LeMDR is possibly involved in the shikonin efflux transport. The accumulation of shikonin is lower in yeast cells transformed with LeMDR-overexpressing vector than that with empty vector. The transgenic hairy roots of L. erythrorhizon overexpressing LeMDR (MDRO) significantly enhanced shikonin production, whereas the RNA interference of LeMDR (MDRi) displayed a reverse trend. Moreover, the mRNA expression level of LeMDR was up-regulated by treatment with shikonin and shikonin-positive regulators, methyl jasmonate and indole-3-acetic acid. There might be a relationship of mutual regulation between the expression level of LeMDR and shikonin biosynthesis.

CONCLUSIONS

Our findings demonstrated the important role of LeMDR in transmembrane transport and biosynthesis of shikonin.

Bioactivity and quantitative analysis of isohexenylnaphthazarins in root periderm of two Echium spp.: E. plantagineum and E. gaditanum

Isohexenylnaphthazarins are commonly found in the root periderm of several Boraginaceous plants and are known for their broad range of biological activities. The work described herein concerns the biological activity of compounds from the roots of Echium plantagineum L. and Echium gaditanum Boiss (Boraginaceae) collected from field sites in southern Spain and Australia. Bioactivity was assessed using etiolated wheat coleoptile bioassay and in vitro growth inhibitory activity in HeLa and IGROV-1 cells. The quantification of four isohexenylnaphthazarins (shikonin/alkannin, deoxyshikonin/deoxyalkannin, acetylshikonin/acetylalkannin and dimethylacrylshikonin/dimethylacrylalkannin) was performed by LC-MS/MS using juglone as internal standard. Correlation coefficient values for the activities and concentrations of these four analytes were in the linear range and were greater than 0.99. Acetylshikonin/acetylalkannin and dimethylacrylshikonin/dimethylacrylalkannin were present in the highest concentrations in extracts of both species. The results reveal that greatest overall inhibition was observed in both bioassays with E. gaditanum extracts. Strong correlations between time of collection, sampling location and bioactivity were identified.

Transcriptome analysis explores genes related to shikonin biosynthesis in Lithospermeae plants and provides insights into Boraginales' evolutionary history

Shikonin and its derivatives extracted from Lithospermeae plants' red roots have current applications in food and pharmaceutical industries. Previous studies have cloned some genes related to shikonin biosynthesis. However, most genes related to shikonin biosynthesis remain unclear, because the lack of the genome/transcriptome of the Lithospermeae plants. Therefore, in order to provide a new understanding of shikonin biosynthesis, we obtained transcriptome data and unigenes expression profiles in three shikonin-producing Lithospermeae plants, i.e., Lithospermum erythrorhizon, Arnebia euchroma and Echium plantagineum. As a result, two unigenes (i.e., G10H and 12OPR) that are involved in "shikonin downstream biosynthesis" and "methyl jasmonate biosynthesis" were deemed to relate to shikonin biosynthesis in this study. Furthermore, we conducted a Lamiids phylogenetic model and identified orthologous unigenes under positive selection in above three Lithospermeae plants. The results indicated Boraginales was more relative to Solanales/Gentianales than to Lamiales.

Metabolic Profiling and Identification of Shikonins in Root Periderm of Two Invasive Echium spp. Weeds in Australia

Metabolic profiling can be successfully implemented to analyse a living system's response to environmental conditions by providing critical information on an organism's physiological state at a particular point in time and allowing for both quantitative and qualitative assessment of a specific subset(s) of key metabolites. Shikonins are highly reactive chemicals that affect various cell signalling pathways and possess antifungal, antibacterial and allelopathic activity. Based on previous bioassay results, bioactive shikonins, are likely to play important roles in the regulation of rhizosphere interactions with neighbouring plants, microbes and herbivores. An effective platform allowing for rapid identification and accurate profiling of numerous structurally similar, difficult-to-separate bioactive isohexenylnaphthazarins (shikonins) was developed using UHPLC Q-TOF MS. Root periderm tissues of the invasive Australian weeds Echium plantagineum and its congener E. vulgare were extracted overnight in ethanol for shikonin profiling. Shikonin production was evaluated at seedling, rosette and flowering stages. Five populations of each species were compared for qualitative and quantitative differences in shikonin formation. Each species showed little populational variation in qualitative shikonin production; however, shikonin was considerably low in one population of E. plantagineum from Western New South Wales. Seedlings of all populations produced the bioactive metabolite acetylshikonin and production was upregulated over time. Mature plants of both species produced significantly higher total levels of shikonins and isovalerylshikonin > dimethylacrylshikonin > shikonin > acetylshikonin in mature E. plantagineum. Although qualitative metabolic profiles in both Echium spp. were nearly identical, shikonin abundance in mature plant periderm was approximately 2.5 times higher in perennial E. vulgare extracts in comparison to those of the annual E. plantagineum. These findings contribute to our understanding of the biosynthesis of shikonins in roots of two related invasive plants and their expression in relation to plant phenological stage.

Antibacterial and cytotoxic activities of naphthoquinone pigments from Onosma visianii Clem

In this study, the antibacterial and cytotoxic activities of isolated compounds from the roots of Onosma visianii were investigated. By using different chromatographic techniques and appropriate spectroscopic methods, the seven naphthoquinones were described: deoxyshikonin (1), isobutyrylshikonin (2), α-methylbutyrylshikonin (3), acetylshikonin (4), β-hydroxyisovalerylshikonin (5), 5,8-O-dimethyl isobutyrylshikonin (6) and 5,8-O-dimethyl deoxyshikonin (7). Among the tested compounds, 3 and 4 exhibited the highest antibacterial activities toward all tested bacterial species (MIC₅₀ and MIC₉₀ for gram positive bacteria: 6.40 μg/mL-12.79 μg/mL and 6.82 μg/mL-13.60 μg/mL, respectively; for gram negative bacteria: 4.27 μg/mL-8.53 μg/mL and 4.77 μg/mL-9.54 μg/mL, respectively). Also, naphthoquinones 3 and 4 exhibited strong cytotoxic activity against MDA-MB-231 cells (IC₅₀ values 86.0 μg/mL and 80.2 μg/mL, respectively), while compounds 1, 3, 4 and 5 significantly decreased viability of HCT116 cells (IC₅₀ values of 97.8 μg/mL, 15.2 μg/mL, 24.6 μg/mL and 30.9 μg/mL, respectively). Our results indicated that all tested naphthoquinone pigments are potential candidates for clinical uses as antibacterial and cytotoxic agents.

Bioassay-guided isolation of wound healing active compounds from Echium species growing in Turkey

ETHNOPHARMACOLOGICAL RELEVANCE

The roots and root barks of Echium sp. have been used to treat ulcers, burns and wounds in traditional Turkish medicine.

AIM OF THE STUDY

On the basis of them traditional use and literature references, four Echium species were selected for evaluation of them wound healing potential. Isolation of active component(s) from the active extracts through the bioassay guided fractionation procedures.

MATERIAL AND METHODS

In vivo the wound healing activity of the plants was evaluated by linear incision experimental models. The chloroform extract of Echium italicum L. was fractionated by successive chromatographic techniques. Wound healing activity of each fraction was investigated following the bioassay-guided fractionation procedures. Moreover, the tissue samples of isolated compounds were examined histopathologically. The healing potential was comparatively assessed with a reference ointment Madecassol®, which contains 1% extract of Centella asiatica.

RESULTS

Significant wound healing activity was observed from the ointment prepared with ethanol extract at 1% concentration. The ethanol root extract treated in groups of animals showed a significant increase (37.38%, 40.97% and 35.29% separately for E. italicum L, Echium vulgare L. and Echium angustifolium Miller) wound tensile strength in the incision wound model. Subfractions showed significant but reduced wound healing activity on in vivo wound models. Shikonin derivatives "Acetylshikonin", "Deoxyshikonin" and "2-methyl-n-butyrylshikonin+Isovalerylshikonin", were isolated and determined as active components of active final subfraction from E. italicum L. roots. The results of histopathological examination supported the outcome of linear incision wound models.

CONCLUSION

The experimental study revealed that Echium species display remarkable wound healing activity.

Identification and localization of bioactive naphthoquinones in the roots and rhizosphere of Paterson's curse (Echium plantagineum), a noxious invader

Bioactive plant secondary products are frequently the drivers of complex rhizosphere interactions, including those with other plants, herbivores and microbiota. These chemically diverse molecules typically accumulate in a highly regulated manner in specialized plant tissues and organelles. We studied the production and localization of bioactive naphthoquinones (NQs) in the roots of Echium plantagineum, an invasive endemic weed in Australia. Roots of E. plantagineum produced red-coloured NQs in the periderm of primary and secondary roots, while seedling root hairs exuded NQs in copious quantities. Confocal imaging and microspectrofluorimetry confirmed that bioactive NQs were deposited in the outer layer of periderm cells in mature roots, resulting in red colouration. Intracellular examination revealed that periderm cells contained numerous small red vesicles for storage and intracellular transport of shikonins, followed by subsequent extracellular deposition. Periderm and root hair extracts of field- and phytotron-grown plants were analysed by UHPLC/Q-ToF MS (ultra high pressure liquid chromatography coupled to quadrupole time of flight mass spectrometry) and contained more than nine individual NQs, with dimethylacrylshikonin, and phytotoxic shikonin, deoxyshikonin and acetylshikonin predominating. In seedlings, shikonins were first found 48h following germination in the root-hypocotyl junction, as well as in root hair exudates. In contrast, the root cortices of both seedling and mature root tissues were devoid of NQs. SPRE (solid phase root zone extraction) microprobes strategically placed in soil surrounding living E. plantagineum plants successfully extracted significant levels of bioactive shikonins from living roots, rhizosphere and bulk soil surrounding roots. These findings suggest important roles for accumulation of shikonins in the root periderm and subsequent rhizodeposition in plant defence, interference, and invasion success.

Systematic identification of shikonins and shikonofurans in medicinal Zicao species using ultra-high performance liquid chromatography quadrupole time of flight tandem mass spectrometry combined with a data mining strategy

Shikonin, shikonofuran and their derivatives are the main bioactive components of Zicao, a traditional Chinese herbal medicine prepared with the dried roots of Lithospermum erythrorhizon, Arnebia euchroma or Arnebia guttata. However, approaches on the systematic discovery and identification of shikonins and shikonofurans, especially unknown ones, are still not available. To address this issue, the gas-phase CID-fragmentation routes for the shikonins and shikonofurans were established by using ESI-QTOF-MS in the negative ion mode and low-energy collision induced dissociation tandem mass spectrometry (CID-MS/MS) in this study using seventeen standards. As a result, diagnostic product ions for rapid discovery and classification of shikonins and shikonofurans were determined. In addition, various mobile phase compositions and UHPLC elution programs were evaluated to achieve optimal separation efficiency and detection response of these types of analytes. Based on these findings, an integral approach using UHPLC-ESI-QTOF-MS and CID-MS/MS analyses together with a novel two steps data mining strategy was developed for systematic analysis of shikonins and shikonofurans in complex samples. Consequently, 58 compounds including 32 novel ones were efficiently discovered and identified from the crude extract of Zicao. Moreover, comparative analyses of the 58 chemical components in three Zicao species including Lithospermum erythrorhizon, Arnebia euchroma and Arnebia guttata samples were conducted using the established analytical method, which can be instructive for future utilization of Zicao and its related medicinal products.

Cytotoxic Compounds from Endemic Arnebia purpurea

Phytochemical studies of the roots and aerial parts of endemic Arnebia purpurea S. Erik & H. Sumbul resulted in the isolation and characterization of four naphthoquinones [isovalerylalkannin (1), α-methyl- n-butanoyl alkannin (2), acetylalkannin (3), and alkannin (4)], a triterpene derivative [3- O-acetyl-oleanolic acid (5)], a steroid [β-sitosterol (6)], three flavonoid glycosides [isorhamnetin-3- O-rutinoside (7), kaempferol-3- O-rutinoside (8), kaempferol 3- O-(5″-acetyl) apiofuranoside 7- O-rhamnopyranoside (9)] and a phenolic acid [rosmarinic acid (10)]. 3- O-Acetyl-oleanolic acid, isorhamnetin-3- O-rutinoside, kaempferol-3- O-rutinoside, and kaempferol 3- O-(5″-acetyl) apiofuranoside 7- O-rhamnopyranoside are reported from an Arnebia species for the first time. Cytotoxic activities on L929 murine fibrosarcoma cell line of the isolated compounds were investigated using MTT assay. Naphthoquinones (1–4) showed intermediate cytotoxic activity in comparison with the standard, doxorubicin.

In vitro and in vivo anticancer effects of Lithospermum erythrorhizon extract on B16F10 murine melanoma

ETHNOPHARMACOLOGICAL RELEVANCE

Lithospermum erythrorhizon has long been used in traditional Asian medicine for the treatment of diseases including skin cancer. In this study, hexane extract from the roots of Lithospermum erythrorhizon (LEH) was chemically characterized and its anticancer activity was tested against the most aggressive form of skin cancer.

MATERIALS AND METHODS

The in vitro anticancer studies viz. cell growth, cell cycle and apoptosis, and the expression of tumor regulating proteins were analyzed against B16F10 melanoma cells. In addition, C57BL/6 mice models were used to evaluate the in vivo anticancer potential of LEH. Mice were intraperitoneally injected with LEH at doses of 0.1 and 10mg/kg every 3 days. The tumor inhibition ratio was determined after 21 days of treatment and the histopathological analyses of the tumor tissues were compared. Further, LEH was purified and its active compounds were structurally elucidated and identified by NMR spectra and quantified by HPLC analyses.

RESULTS

LEH effectively inhibits the growth of melanoma cells with an IC(50) of 2.73μg/ml. Cell cycle analysis revealed that LEH increased the percentage of cells in sub-G1 phase by dose dependent manner. LEH exhibited down regulation of anti-apoptotic Bcl-2 family proteins and up regulation of apoptotic Bax protein expression. Importantly, LEH induced cleavage of poly (ADP-ribose) polymerase (PARP) and activated the caspase cascade (caspase 3) with this cleavage mediating the apoptosis of B16F10 cells. LEH treatment at a dose of 10mg/kg for 21 days in experimental mice implanted with tumors resulted in significant reduction of the tumor growth (43%) and weight (36%). Histopathology analysis of LEH treated tumor tissues showed evidence of increased necrotic cells in a concentration dependent manner. Meanwhile, five naphthoquinone compounds [Shikonin (1); Deoxyshikonin (2); β-Hydroxyisovalerylshikonin (3); Acetylshikonin (4) and Isobutyrylshikonin (5)] were purified from LEH and responsible for its anticancer activity.

CONCLUSION

LEH induced apoptosis in B16F10 cells by activation of caspase 3 and inducing sub-G1 cell cycle arrest. LEH exhibited both in vitro and in vivo anticancer activity. Shikonin derivatives in the LEH are responsible for the anticancer activity.

Addition of β-lactoglobulin produces water-soluble shikonin

Shikonin and its ester derivatives belong to a group of secondary metabolites with a wide array of beneficial effects on human health. However, shikonin is principally used in oil-based preparations due to the low solubility of the pigment in aqueous media, and the positive properties of shikonin are not exploited to their full potential. Such low aqueous solubility often results in poor bioavailability, makes shikonin undesirable for oral administration, and restricts its broadened use in the food and pharmaceutical industries. The purpose of this study was to enhance the aqueous solubility of shikonin by the addition of β-lactoglobulin and to characterize the macromolecule-ligand binding interaction by means of spectrophotometry, spectrofluorometry, high-performance liquid chromatography, and mass spectrometry. In the presence of β-lactoglobulin the solubility of shikonin is increased up to 181-fold. One shikonin molecule binds covalently to β-lactoglobulin via Cys(121), whereas the remaining pigment molecules most probably bind to the protein via noncovalent interactions.

A Study of the Wound Healing Mechanism of a Traditional Chinese Medicine, Angelica sinensis, Using a Proteomic Approach

Angelica sinensis (AS) is a traditional Chinese herbal medicine that has been formulated clinically to treat various form of skin trauma and to help wound healing. However, the mechanism by which it works remains a mystery. In this study we have established a new platform to evaluate the pharmacological effects of total AS herbal extracts as well as its major active component, ferulic acid (FA), using proteomic and biochemical analysis. Cytotoxic and proliferation-promoting concentrations of AS ethanol extracts (AS extract) and FA were tested, and then the cell extracts were subject to 2D PAGE analysis. We found 51 differentially expressed protein spots, and these were identified by mass spectrometry. Furthermore, biomolecular assays, involving collagen secretion, migration, and ROS measurements, gave results that are consistent with the proteomic analysis. In this work, we have demonstrated a whole range of pharmacological effects associated with Angelica sinensis that might be beneficial when developing a wound healing pharmaceutical formulation for the herbal medicine.

Selective and slow-binding inhibition of shikonin derivatives isolated from Lithospermum erythrorhizon on glycosyl hydrolase 33 and 34 sialidases

Sialidases are enzymes that catalyze the hydrolysis of sialic acid residues from various glycoconjugates, which are widely found in a number of viral and microbial pathogens. In this study, we investigated the biological evaluation of isolated six shikonins (1-6) and three shikonofurans (7-9) from Lithospermum erythrorhizon. The nine isolated compounds 1-9 showed strong and selective inhibition of glycosyl hydrolase (GH) 33 and -34 sialidases activities. In GH33 bacterial-sialidase inhibition assay, the inhibitory activities against GH33 siadliase of all shikonofuran derivatives (7-9) were greater than shikonin derivatives (1-6). Shikonofuran E (8) exhibited the most potent inhibitory activity toward GH33 sialidases (IC(50)=0.24μM). Moreover, our detailed kinetic analysis of these species unveiled that they are all competitive and simple reversible slow-binding inhibitors. Otherwise, they showed different inhibitory capacities and kinetic modes to GH34 viral-sialidase activity. All the naphthoquinone derivatives (1-6) were of almost equal efficiency with IC(50) value of 40μM and shikonofurans (7-9) did not show the significant inhibitory effect to GH34 sialidase. Kinetic analyses indicated that naphthoquinones acted via a noncompetitive mechanism.

Anxiolytic and Hypnotic Effects of Aqueous and Ethanolic Extracts of Aerial Parts of Echium italicum L. in Mice

BACKGROUND

Research in the area of herbal psychopharmacology has clearly improved in recent decades. Self-administration of herbal medicines has been the most popular therapeutic alternative to standard medicine.

OBJECTIVES

Since the extract of Echium amoenum exhibits an anxiolytic effect, the aim of this study is to evaluate the anxiolytic and hypnotic effects in mice of the aqueous and ethanolic extracts of aerial parts of E. italicum, a member of the Boraginaceae family.

MATERIALS AND METHODS

Mice were administered the agents intraperitoneally before the start of the experiments for evaluation of hypnotic activity (induced by sodium pentobarbital, 30 mg/kg, i.p.), anxiolytic activity (elevated plus-maze [EPM] test), locomotor activity (open field test), and motor coordination (rotarod test).

RESULT

The ethanolic and aqueous extracts of E. italicum, at doses of 1.2 and 2.1 g/kg, increased the percentage of time-spent and the percentage of arm entries in the open arms of the EPM and decreased the percentage of time-spent in the closed arms of the EPM. Moreover, both extracts decreased the pentobarbital-induced latency to sleep and significantly increased the total sleeping time induced by pentobarbital. In addition, locomotor activity was affected by aqueous extracts and ethanolic extract (at higher doses). Both extracts showed no effect in the rotarod test.

CONCLUSIONS

These results suggest that both ethanolic and aqueous extracts of E. italicum may have anxiolytic effects and sedative activity but no effect on muscle relaxation.