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.

Phylogenomics and plastome evolution of Lithospermeae (Boraginaceae).

BACKGROUND: Lithospermeae is the largest tribe within Boraginaceae. The tribe has been the focus of multiple phylogenetic studies over the last 15 years, with most focused on one genus or a few genera. In the present study, we newly sequenced 69 species of Lithospermeae and relatives to analyze the phylogenomic relationships among its members as well as the evolution of the plastid genome. RESULTS: The phylogeny of Lithospermeae resolved from the plastid genome and nrDNA cistron is generally congruent with prior studies, but is better resolved and supported. Increasing character sampling across the plastid genome results in gradually more similar trees to that from the entire plastid genome. Overall, plastid genome structure was quite consistent across Lithospermeae. Codon Usage Bias (CUB) analyses demonstrate that across Lithospermeae plastid genomes were rich in AT and poor in GC. Mutation may play a greater role than selection across the plastid genome of Lithospermeae. The present study is the first to highlight the CUB characteristics of Lithospermeae species, which can help elucidate the mechanisms underlying patterns of molecular evolution and improve the expression levels of exogenous genes by codon optimization. CONCLUSIONS: This study provides a comprehensive phylogenomic analysis of Lithospermeae, significantly enhancing our understanding of the phylogenetic relationships and plastid genome evolution within this largest tribe of Boraginaceae. By utilizing an expanded genomic sampling approach, we have achieved increased resolution and support among the evolutionary relationships of the tribe, in line with but improving upon previous studies. The analyses of plastid genome structure revealed consistency across Lithospermeae, with a notable CUB. This study marks the first investigation into the CUB of Lithospermeae species and sets the stage for further research on the molecular evolution of plastid genomes across Boraginaceae.

Anoikis and cancer cell differentiation: novel modes of shikonin derivatives anticancer action in vitro.

BACKGROUND: Shikonin is a naturally occurring naphthoquinone found in the roots of several genera of the Boraginaceae family, widely known for its numerous biological activities, such as antiinflammatory, antioxidant, antimicrobial and anticancer. In this study, the antitumor effect of six naphthoquinones isolated from the roots of Onosma visianii was evaluated using two cell lines, mouse melanoma B16 and highly aggressive rat glioma cell line C6. METHODS AND RESULTS: All examined shikonins dose-dependently decreased the viability of tested cells, with compounds 5 and 6 being the most potent ones and hence subjected to further analysis. The diminished viability of B16 melanoma cells was in correlation with detected caspase-mediated apoptosis. Importantly, observed altered cell morphology along with the loss of dividing potential upon exposure to both shikonins implied reprogram of B16 cell phenotype. Elevated expression of myelin basic protein indicated the acquirement of Schwann-like cell phenotype, while detected autophagy might be connected to this phenomenon. On the contrary, upon exposure to both agents, C6 cells underwent specific cell death-anoikis, provoked by detachment from the extracellular matrix and compromised integrin signaling. Oppositely to compound 5, compound 6 realized anoikis in a caspase-independent manner and under sustained ERK1/2 activation, indicating the deviation from standard proanoikis signaling. CONCLUSIONS: Herein, we have pointed out the diversity and novelty in the mode of action of shikonin derivatives depending on the tumor cell features, which represents a good platform for new investigations of these promising natural compounds.

Pleonotoquinones, Cytotoxic Oxepinenaphthoquinones from Pleonotoma jasminifolia.

Two unusual naphthoquinones, named here as pleonotoquinones A (1) and B (2), were isolated along with two known anthraquinones (3 and 4) via chromatographic separations of an ethyl acetate extract of the roots of Pleonotoma jasminifolia. Compounds 1 and 2 are the first examples of quinones bearing a 2-methyloxepine moiety. The compounds were isolated with the aid of mass spectrometry and molecular networking, and their structures were resolved using 1D and 2D NMR and HRESIMS data. The isolated compounds were evaluated for their antiproliferative activity against human cancer cell lines, and compounds 1 and 2 displayed cytotoxicity against human colon cancer HCT116 cells (IC50 = 2.6 µM for compound 1 and IC50 = 4.3 µM for compound 2) and human liver cancer HepG2 cells (IC50 = 1.9 µM for compound 1 and IC50 = 6.4 µM for compound 2).

A class of geranylquinol-derived polycyclic meroterpenoids from Arnebia euchroma against heart failure by reducing excessive autophagy and apoptosis in cardiomyocytes.

Ten new B-ring aromatized 6/6/6-tricyclic dearomatized benzocogeijerene-based meroterpenoids with unusual methyl 1,2-shift or demethylation (2-9b), and two new geranylquinol derivatives (1 and 10), together with two known compounds (11 and 12), were isolated from the roots of Arnebia euchroma. Their structures were elucidated by extensive spectroscopic methods, X-ray diffraction crystallography, and ECD calculations. The plausible biosynthetic pathways including the unusual methyl 1,2-shfit and demethylation for B-ring aromatized 6/6/6-tricyclic meroterpenoids were discussed. Compounds 1, 2, 5, 6, 11, and 12 showed significant cardioprotective activities comparable to diltiazem against isoprenaline (ISO)-induced H9C2 cell damage in vitro. Compound 11 probably exerted heart-protective effect on ISO-induced H9C2 cells by modulating the PI3K-AKT-mTOR pathway, reducing excessive autophagy, and decreasing myocardial apoptosis.

Pyrrolizidine alkaloids are synthesized and accumulated in flower of Myosotis scorpioides.

Pyrrolizidine alkaloids (PAs) are specialized metabolites that are produced by various plant families that act as defense compounds against herbivores. On the other hand, certain lepidopteran insects uptake and utilize these PAs as defense compounds against their predators and as precursors of their sex pheromones. Adult males of Parantica sita, a danaine butterfly, convert PAs into their sex pheromones. In early summer, P. sita swarms over the flowers of Myosotis scorpioides, which belongs to the family Boraginaceae. M. scorpioides produces PAs, but the organs in which PAs are produced and whether P. sita utilizes PAs in M. scorpioides are largely unknown. In the present study, we clarified that M. scorpioides accumulates retronecine-core PAs in N-oxide form in all organs, including flowers. We also identified two M. scorpioides genes encoding homospermidine synthase (HSS), a key enzyme in the PA biosynthetic pathway, and clarified that these genes are expressed in all organs where PAs accumulate. Phylogenetic analysis suggested that these two HSS genes were originated from gene duplication of deoxyhypusine synthase gene like other HSS genes in PA-producing plants. These results suggest that PAs are synthesized and accumulated in the flower of M. scorpioides and provide a possibility for a PA-mediated interaction between P. sita and M. scorpioides.

Effect of robbing intensity on reproductive success of Symphytum officinale (Boraginaceae).

The intervention of nectar robbers in plant pollination systems will cause some pollinators to modify their foraging behavior to act as secondary robbers, consequently adopting a mixed foraging strategy. The influence of nectar robbing on pollinator behavior may be affected by spatio-temporal difference of robbing intensity, and consequently, may have different effects on the pollination of host plants. However, whether and how the nectar robbing might influence pollinators under different robbing intensity still needs further investigation. In this study, Symphytum officinale was used to detect the effect of nectar robbers on pollinators under different robbing intensity as well as their effects on plant reproductive success. Six robbing levels and three bumblebees with mixed foraging behaviors were used to evaluate the effect of different robbing intensity on pollinator behavior, visitation rate, flower longevity and pollen deposition. Our results indicated that the robbing rate increased gradually with the proportion of robbed flowers, but which did not affect the frequency of legitimate visits. The increase of robbing rate promoted the corolla abscission, and then enhanced the self-pollen deposition, but which had no significant effect on cross-pollen deposition. These results indicate that the overall fitness of S. officinale was improved by combined self and cross-pollination modes when visited by both pollinators and nectar robbers simultaneously. Although nectar robbing is not uncommon, its consequences for pollination in the interaction web have not been well studied. Our results emphasize the significance of indirect impacts in mediating the adaptive outcomes of species interactions.

Effects of Naphthoquinones from the Roots of Onosma Armeniacum Klokov on Wound Healing.

In Turkish folk medicine, the roots of Onosma armeniacum Klokov are used to heal wounds, burns, hemorrhoids, hoarseness, dyspnea, stomach ulcers, and abdominal aches. The objective was to evaluate the plant's ethnopharmacological applications using in vivo pharmacological experimental models. In vivo linear incision and circular excision the wound models were used to assess the wound healing activity along with histopathological investigation. The active component(s) were isolated and identified after being exposed to several chromatographic separation procedures on the primary extract. The n-hexane-dichloromethane mixture extract was subjected to chromatographic separation after the wound-healing activity was confirmed. Deoxyshikonin (1), ß,ß-dimethylacrylshikonin (2), α-methyl-n-butylshikonin (3), isovalerylshikonin (4), acetylshikonin (5), ß-hydroxyisovalerylshikonin (6), and 5,8-O-dimethylacetylshikonin (7) were identified as the structures of the isolated compounds. The efficacy of O. armeniacum to heal wounds was investigated in this study. Shikonin derivatives were identified as the primary active components of the roots by bioassay-guided fractionation and isolation procedures.

The healing effect of a mixture of Arnebia euchroma and animal fat on burn wounds in rats in comparison with sulfadiazine.

OBJECTIVE: Thermal burn is a serious cause of morbidity and mortality that affects millions of people worldwide. The aim of this experimental study was to investigate the efficacy of Arnebia euchroma (AE) to treat burn wounds in a rat model. METHOD: A total of 80 male rats (200-250g) were shaved over the back of the neck (2×3cm2) and a second-degree burn wound was induced at this site under general anaesthesia. The rats were then randomly assigned to one of four groups (each n=20) and the burns were treated daily for 14 days as follows: (1) dressed with animal fat; (2) dressed with sulfadiazine; (3) dressed with a mixture of AE and animal fat; (4) no treatment (control). Five rats from each group were sacrificed on days 3, 5, 9 and 14 post-burn and the wounds were evaluated histologically and immunohistochemically for the expression of interleukin (IL)-1 and IL-6. RESULTS: There was a significant increase at day 3 and decrease on day 5 samples for the expression of IL-1 in the AE plus fat group and IL-6 in the AE plus fat and sulfadiazine groups, compared to the control and fat treatment groups, respectively. Both AE plus fat and sulfadiazine treatments reduced inflammation and granulation tissue formation by day 5 post-burn, while re-epithelialisation commenced by day 9 post-burn. In addition, burns treated with AE plus fat exhibited keratinised epidermis, associated with regular collagen fibres, compared to moderately dense collagen fibres without vascularisation in the sulfadiazine group. CONCLUSION: These findings suggested that AE plus fat was superior to sulfadiazine in enhancing burn wound healing in rats.

Healing of Skin Wounds in Rats Using Creams Based on Symphytum Officinale Extract.

Rosmarinic acid is a well-known natural antioxidant and anti-inflammatory compound, and it is one of the polyphenolic compounds found in comfrey plants. Comfrey root also contains allantoin, which helps with new skin regeneration. This study aimed to investigate the healing and skin regeneration process of skin wounds in Wistar rats using creams based on comfrey extract and to correlate the results with active compounds in the extract. The obtained results showed that comfrey root is rich in bioactive compounds, including allantoin, salvianolic acid, and rosmarinic acid, which are known for their great free radical scavenging activity, and the high antioxidant activity of the extract may be mainly due to these compounds. The obtained extract has an antimicrobial effect on Staphylococcus aureus (1530.76/382.69), Escherichia coli (6123.01/6123.01), and Pseudomonas aeruginosa (6123.01/6123.01). The macroscopic evaluation and the histological analysis of the skin defects 14 days after the intervention showed faster healing and complete healing in the skin excisions treated with oil-in-water cream with 20% extract of comfrey as the active ingredient.

The extraction and anti-inflammatory screening of Onosma glomeratum Y. L. Liu.

"Zicao" has a long medicinal history and has a variety of pharmacological activities. As the main resource of "zicao" in Tibet, Onosma glomeratum Y. L. Liu (tuan hua dian zi cao), usually used for treating pneumonia in Tibet, has not been reported deeply. In order to determine the main anti-inflammatory active ingredients of Onosma glomeratum Y. L. Liu, in this study, the extracts enriched in naphthoquinones and polysaccharides were optimized prepared form Onosma glomeratum Y. L. Liu by ultrasonic extraction, and reflux extraction, respectively, with Box-Behnken design effect surface method. And their anti-inflammatory abilities were screened on LPS induced A549 cells model, for figuring out the anti-inflammatory active ingredients from Onosma glomeratum Y. L. Liu.The extract enriched naphthoquinone was obtained under following condition: extract with 85% ethanol in a liquid to material ratio of 1:40 g/mL at 30 °C for 30 minutes using ultrasound, leading to the extraction rate of total naphthoquinone as 0.98 ± 0.017%; the extract enriched polysaccharides was prepared as follows: extract 82 minutes at 100 °C with distilled water in a liquid to material ratio of 1:50 g/mL, with extraction rate of polysaccharide as 7.07 ± 0.02%.On the LPS-induced A549 cell model, the polysaccharide extract from Onosma glomeratum Y. L. Liu showed better anti-inflammatory effects than the naphthoquinone extract, indicating the extract enriched in polysaccharides is the anti-inflammatory extract of Onosma glomeratum Y. L. Liu, which could serve as a potential anti-inflammatory extract in medical and food industries in the future.

Exploring the Biological and Phytochemical Potential of Jordan's Flora: A Review and Update of Eight Selected Genera from Mediterranean Region.

Jordan's flora is known for its rich diversity, with a grand sum of 2978 plant species that span 142 families and 868 genera across four different zones. Eight genera belonging to four different plant families have been recognized for their potential natural medicinal properties within the Mediterranean region. These genera include Chrysanthemum L., Onopordum Vaill. Ex. L., Phagnalon Cass., and Senecio L. from the Asteraceae family, in addition to Clematis L. and Ranunculus L. from the Ranunculaceae family, Anchusa L. from the Boraginaceae family, and Eryngium L. from the Apiaceae family. The selected genera show a wide variety of secondary metabolites with encouraging pharmacological characteristics including antioxidant, antibacterial, cytotoxic, anti-inflammatory, antidiabetic, anti-ulcer, and neuroprotective actions. Further research on these genera and their extracts will potentially result in the formulation of novel and potent natural pharmaceuticals. Overall, Jordan's rich flora provides a valuable resource for exploring and discovering new plant-based medicines.

A natural approach to breast cancer treatment: investigation of chemical features of aerial parts of endemic Onosma sintenisii Hausskn. ex Bornm and its antioxidant properties, in vitro cytotoxic and apoptosis induction on MCF-7 cells.

Onosma sintenisii Hausskn. ex Bornm. (O. sintenisii) belongs to the Boraginaceae family and it is an endemic species from Irano-turanian phytogeographical region (central and eastern Anatolia) that distributes in steppe areas. This study aimed to investigate the chemical composition, antioxidant, in vitro cytotoxic and apoptosis induction of methanol extract of aerial parts of O. sintenisii. As a result of GC/MS analysis, 14 components were identified, and the major compounds of the extracts are retronecine (13.94%), α.-D-Glucopyranosiduronic acid (10.86%), melaniline (7.5%) and 1,2-Butanediol (4.02%), respectively. Antioxidant properties of O. sintenisii were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferric reducing antioxidant power (FRAP) and superoxide radical scavenging activity methods. While the DPPH free radical scavenging activity results of O. sintenisii extract varied between 62.49% and 32.27%, reducing power activity and superoxide radical scavenging activity were found to be low. The result of the MTT assay revealed strong anticancer activity of O. sintenisii extract. The most significant cytotoxic effect was noted at a concentration of 1000 µg/mL after 48 hours. These findings together with flow cytometry analysis suggest that apoptosis can be the main mechanism underlying cell death after O. sintenisii extract treatment.

Phytochemical Characteristics and Antimicrobial Effects of Nonea rossica (Boraginaceae) Extracts.

Phytochemical characteristics and antimicrobial properties of extracts were studied in Nonea rossica Steven (Boraginaceae), which is widespread in Russia. The aerial part (herb) of N. rossica was harvested from a steppe meadow in the Novosibirsk region during flowering. The qualitative composition of biologically active compounds (BACs) was determined by thin-layer chromatography. Quantitative assays were carried out by spectrophotometry; flavonoids, hydroxycinnamic acids, and coumarin-like compounds were measured with reference to rutin, caffeic acid, and coumarin, respectively. Antimicrobial activity was determined by the serial dilution method. Gram-positive bacterial (Staphylococcus aureus ATCC 6538 FDA 209P and Bacillus cereus ATCC 10702) and fungal (Candida albicans NCTC 885-653) strains were used as test cultures. Phenolic BACs (hydroxycinnamic acids, flavonoids, and coumarins) were detected, and their quantitative contents determined. The highest yield of phenolic BACs was achieved using 40-70% ethanol as an extractant. Antimicrobial activity against S. aureus and B. cereus and antifungal activity against C. albicans were detected in N. rossica herb extracts prepared using 40-70% ethanol. The extracts were tested for the contents of caffeic acid and coumarin. Synergistic interactions of these compounds determined the bactericidal and fungistatic properties of the extracts.

Investigation of the Chemical Composition, Antimicrobial, and Antioxidant Activity of Endemic Onosma halophila Boiss. & Heldr.

The Onosma halophila Boiss. & Heldr. belongs to the Boraginaceae family and it is endemic species from Turkey that distributes in Salt Lake (Tuz Gölü) and the surrounding salty steppes. In this study, the chemical content, antimicrobial, and antioxidant activity of endemic O. halophila were determined for the first time. Thirty-one components were identified by GC-MS analysis in O. halophila. Antimicrobial activity was tested against a total of eight microorganisms, including three Gram-positive, three Gram-negative bacterial strains, and two fungal strains, using the Micro dilution technique. The obtained extracts showed strong antifungal and antibacterial activity. The MIC value of extracts samples against the tested strains ranged from 15.625 to 125 µg/mL. In addition, it was determined that the extracts had different levels of antioxidant activity. The IC50 values were determined 45.20-1760 µg/mL for DPPH radical scavenging assay, 3.125-1016 µg/mL for H2O2 radical scavenging assay, and 147.12-1837 µg/mL for superoxide radical scavenging assay, respectively. As a result, it has been determined that O. halophila has the potential to be used in complementary medicine and various ethnobotanical fields in future due to the important components it contains.

Extraction, Distribution and Diversity of Phenolic Compounds in Most Widespread Boraginaceae Species from Macedonia.

A systematic study of extraction efficiency of polyphenolic compounds from the most widespread Boraginaceae species was carried out. The optimal extraction was achieved with 50 % (V/V) methanol for phenolic acids and flavonoids, 0.2 % (V/V) HCl in 50 % (V/V) methanol for anthocyanins and pure water for flavan-3-ols. The distribution and diversity of polyphenolic compounds in plant material obtained from wild-growing Anchusa officinalis, Cynoglossum creticum Mill., Echium vulgare, Echium italicum, and Onosma heterophylla Griseb. species from Macedonia was also assessed. These widespread Boraginaceae species contain phenolic acid derivatives, flavonoids, flavan-3-ols and anthocyanins and in total 31 of them were identified, from which 22 were first identified in the representative species, and 6,8-di-C-glucosides of apigenin and luteolin were identified for the first time in Boraginaceae. The profiles of polyphenolic compounds for each sample were obtained and their phytochemical profile established. The potential for further bioactivity studies of Anchusa officinalis and Cynoglossum creticum containing up to 24577.05 µg/g and 14304.15 µg/g of total polyphenols were assumed to be highest, followed by Echium vulgare (from 6382.61 to 14114.33 µg/g), Onosma heterophylla (9463.97 µg/g) and Echium (4108.14 µg/g).

Antimycobacterial Compound of Cynoglossum lanceolatum Forsk.: Bioassay Guided Isolation, Molecular Docking, Synthesis of Analogs, and a Plausible Mechanism of Action.

Tuberculosis (TB) remains a major threat to human health. Due to the prevalence of drug-resistant Mycobacterium tuberculosis (Mtb), it is urgent to discover drugs with new mechanisms of action (MOA) to ensure effectiveness against strains that are resistant to existing TB drugs. Cynoglossum lanceolatum Forsk was used to treat TB in Traditional Chinese Medicine. In this article, shikonin, the anti-Mtb active component, was obtained from the whole herb extract of C. lanceolatum by bioassay-guided isolation. Using the microplate alamar blue assay (MABA), the minimum inhibitory concentration (MIC) of shikonin against Mtb was determined to be 128 µg/mL. In order to obtain a more efficient anti-Mtb molecule, (E)-1-(6-bromo-2,3-dihydrochromen-4-ylidene)thiosemicarbazide was synthesized based on the scaffold of shikonin, which exhibited potent activity against Mtb (MIC=4 µg/mL). These results highlight that both naphthalene-1,4-dione and chroman-4-one are pharmacophores with activities against Mtb. To investigate a plausible mechanism of action, the molecular docking was firstly performed against catalase-peroxidase enzyme (KatG) of Mtb using AutoDock 4 software. The results demonstrated that both shikonin and (E)-1-(6-bromo-2,3-dihydrochromen-4-ylidene)thiosemicarbazide could bind to the active site of Mtb KatG. KatG enzyme activity and intracellular reactive oxygen species (ROS) levels in Mtb cells were then measured by ultraviolet spectrophotometric method and fluorescence microplate reader assay, respectively. The experiments confirmed that above compounds could inhibit the catalytic activity of Mtb KatG, and cause the ROS accumulation in Mtb cells. Therefore, inhibition of KatG may be a novel mechanism of action for these two compounds to fight against Mtb.

Rindera graeca (A. DC.) Boiss. & Heldr. (Boraginaceae) In Vitro Cultures Targeting Lithospermic Acid B and Rosmarinic Acid Production.

The in vitro cultures of Rindera graeca, a rare endemic plant, were developed as a sustainable source of phenolic acids. Various shoot and root cultures were established and scaled up in a sprinkle bioreactor. A multiplication rate of 7.2 shoots per explant was achieved. HPLC-PDA-ESI-HRMS analysis revealed the presence of rosmarinic acid (RA) and lithospermic acid B (LAB) as the main secondary metabolites in both the shoot and root cultures. The maximum RA (30.0 ± 3.2 mg/g DW) and LAB (49.3 ± 15.5 mg/g DW) yields were determined in root-regenerated shoots. The strongest free radical scavenging activity (87.4 ± 1.1%), according to 2,2-diphenyl-1-picrylhydrazyl-hydrate assay, was noted for roots cultivated in a DCR medium. The highest reducing power (2.3 µM ± 0.4 TE/g DW), determined by the ferric-reducing antioxidant power assay, was noted for shoots cultivated on an SH medium containing 0.5 mg/L 6-benzylaminopurine. A genetic analysis performed using random amplified polymorphic DNA and start codon targeted markers revealed genetic variation of 62.8% to 96.5% among the investigated shoots and roots. This variability reflects the capacity of cultivated shoots and roots to produce phenolic compounds.

LC-MS/MS Evaluation of Pyrrolizidine Alkaloids Profile in Relation to Safety of Comfrey Roots and Leaves from Polish Sources.

Comfrey (Symphytum officinale L.) has a long tradition of use in the treatment of musculoskeletal disorders. However, due to hepatotoxic pyrrolizidine alkaloids (PAs), the EMA restricts the use of comfrey root (CR) to external use only and for short periods of time. Recent studies indicate a low permeability of PAs across the skin, calling into question the safety of topical application of products containing comfrey preparations. The aim of our work was to develop and validate an HPLC method enabling the separation of isomeric PAs from comfrey and, on this basis, to assess the potential toxicity of CR and comfrey leaf (CL) obtained from various Polish sources. The qualitative and quantitative analysis of PAs via HPLC-MS/MS was performed in MRM mode. The results obtained confirmed a lower content of PAs in CL than in CR and showed a wide variation in the composition of PAs in CR, with a much more stable profile of PAs in CL. Factor analysis confirmed that CRs and CLs differ in PA content, which is influenced by the growth conditions and geographical origin. The determined concentrations of PAs prove that in some CRs available on the Polish herbal market, the content of PAs may exceed the daily dose considered safe.

Subcritical Water Extraction of Onosma mutabilis: Process Optimization and Chemical Profile of the Extracts.

The aboveground and root parts of Onosma mutabilis were extracted using subcritical water and the process was optimized with response surface methodology. The composition of the extracts was determined by chromatographic methods and compared to that of conventional maceration of the plant. The optimum total phenolic contents for the aboveground part and the roots were 193.9 and 174.4 µg/g, respectively. These results were achieved at a subcritical water temperature of 150 °C, an extraction time of 180 min, and a water/plant ratio of 0.1, for both parts of the plant. Principal component analysis revealed that the roots contained mainly phenols, ketones, and diols, with the aboveground part mostly alkenes and pyrazines, whereas the extract from maceration contained mainly terpenes, esters, furans, and organic acids. The quantification of selected phenolic substances showed that subcritical water extraction compared favorably to maceration, especially with respect to pyrocatechol (1062 as compared to 10.2 µg/g) and epicatechin (1109 as compared to 23.4 µg/g). Furthermore, the roots of the plant contained twice as much of these two phenolics compared to the aboveground part. Subcritical water extraction of O. mutabilis is an environmentally friendly method that can extract selected phenolics at higher concentrations compared to maceration.