The use of plants containing genotoxic carcinogens as foods and medicine

In vitro Safety Assessment of Extracts and Compounds From Plants as Sunscreen Ingredients

This work investigated the safety of extracts obtained from plants growing in Colombia, which have previously shown UV-filter/antigenotoxic properties. The compounds in plant extracts obtained by the supercritical fluid (CO2) extraction method were identified using gas chromatography coupled to mass spectrometry (GC/MS) analysis. Cytotoxicity measured as cytotoxic concentration 50% (CC50) and genotoxicity of the plant extracts and some compounds were studied in human fibroblasts using the trypan blue exclusion assay and the Comet assay, respectively. The extracts from Pipper eriopodon and Salvia aratocensis species and the compound trans-β-caryophyllene were clearly cytotoxic to human fibroblasts. Conversely, Achyrocline satureioides, Chromolaena pellia, and Lippia origanoides extracts were relatively less cytotoxic with CC50 values of 173, 184, and 89 μg/mL, respectively. The C. pellia and L. origanoides extracts produced some degree of DNA breaks at cytotoxic concentrations. The cytotoxicity of the studied compounds was as follows, with lower CC50 values representing the most cytotoxic compounds: resveratrol (91 μM) > pinocembrin (144 μM) > quercetin (222 μM) > titanium dioxide (704 μM). Quercetin was unique among the compounds assayed in being genotoxic to human fibroblasts. Our work indicates that phytochemicals can be cytotoxic and genotoxic, demonstrating the need to establish safe concentrations of these extracts for their potential use in cosmetics.

Base Excision DNA Repair in Plants: Arabidopsis and Beyond

Base excision DNA repair (BER) is a key pathway safeguarding the genome of all living organisms from damage caused by both intrinsic and environmental factors. Most present knowledge about BER comes from studies of human cells, E. coli, and yeast. Plants may be under an even heavier DNA damage threat from abiotic stress, reactive oxygen species leaking from the photosynthetic system, and reactive secondary metabolites. In general, BER in plant species is similar to that in humans and model organisms, but several important details are specific to plants. Here, we review the current state of knowledge about BER in plants, with special attention paid to its unique features, such as the existence of active epigenetic demethylation based on the BER machinery, the unexplained diversity of alkylation damage repair enzymes, and the differences in the processing of abasic sites that appear either spontaneously or are generated as BER intermediates. Understanding the biochemistry of plant DNA repair, especially in species other than the Arabidopsis model, is important for future efforts to develop new crop varieties.

Occurrence of Alkenylbenzenes in Plants: Flavours and Possibly Toxic Plant Metabolites

Alkenylbenzenes are naturally occurring secondary plant metabolites. While some of them are proven genotoxic carcinogens, other derivatives need further evaluation to clarify their toxicological properties. Furthermore, data on the occurrence of various alkenylbenzenes in plants, and especially in food products, are still limited. In this review, we tempt to give an overview of the occurrence of potentially toxic alkenylbenzenes in essential oils and extracts from plants used for flavoring purposes of foods. A focus is layed on widely known genotoxic alkenylbenzenes, such as safrole, methyleugenol, and estragole. However, essential oils and extracts that contain other alkenylbenzenes and are also often used for flavoring purposes are considered. This review may re-raise awareness of the need for quantitative occurrence data for alkenylbenzenes in certain plants but especially in final plant food supplements, processed foods, and flavored beverages as the basis for a more reliable exposure assessment of alkenylbenzenes in the future.

A Computational Inter-Species Study on Safrole Phase I Metabolism-Dependent Bioactivation: A Mechanistic Insight into the Study of Possible Differences among Species

Safrole, a 162.2 Da natural compound belonging to the alkenylbenzenes class, is classified as a possible carcinogen to humans by IARC (group IIB) and has proven to be genotoxic and carcinogenic to rodents. Despite its use as a food or feed additive, it is forbidden in many countries due to its documented toxicity; yet, it is still broadly present within food and feed and is particularly abundant in spices, herbs and essential oils. Specifically, safrole may exert its toxicity upon bioactivation to its proximate carcinogen 1'-hydroxy-safrole via specific members of the cytochrome P450 protein family with a certain inter/intra-species variability. To investigate this variability, an in-silico workflow based on molecular modelling, docking and molecular dynamics has been successfully applied. This work highlighted the mechanistic basis underpinning differences among humans, cats, chickens, goats, sheep, dogs, mice, pigs, rats and rabbits. The chosen metric to estimate the likeliness of formation of 1'-hydroxy-safrole by the species-specific cytochrome P450 under investigation allowed for the provision of a knowledge-based ground to rationally design and prioritise further experiments and deepen the current understanding of alkenylbenzenes bioactivation and CYPs mechanics. Both are crucial for a more informed framework of analysis for safrole toxicity.

Metabolomic profile and computational analysis for the identification of the potential anti-inflammatory mechanisms of action of the traditional medicinal plants Ocimum basilicum and Ocimum tenuiflorum

Ocimum basilicum and Ocimum tenuiflorum are two basil species widely used medicinally as an anti-inflammatory, antimicrobial and cardioprotective agent. This study focuses on the chemical characterization of the majoritarian compounds of both species and their anti-inflammatory potential. Up to 22 compounds such as various types of salvianolic acids, derivatives of rosmaniric acid and flavones were identified in both plants. The identified compounds were very similar between both plants and are consistent with previous finding in other studies in Portugal and Italy. Based on the identified molecules a consensus target prediction was carried out. Among the main predicted target proteins, we found a high representation of the carbonic anhydrase family (CA2, CA7 and CA12) and several key proteins from the arachidonic pathway (LOX5, PLA2, COX1 and COX2). Both pathways are well related to inflammation. The interaction between the compounds and these targets were explored through molecular docking and molecular dynamics simulation. Our results suggest that some molecules present in both plants can induce an anti-inflammatory response through a non-steroidal mechanism of action connected to the carbon dioxide metabolism.

Toxicological safety assessment of essential oils used as food supplements to establish safe oral recommended doses

Essential oils (EOs) are increasingly consumed as food supplements. The few published recommended doses available generally lack details both on the methodology used and concentration limits for substances of concern, including genotoxic carcinogens. We propose a tiered approach based on the toxicological evaluation of maximized concentrations of each constituent present in the EO investigated. The genotoxic potential of each constituent is assessed using literature data or QSAR analyses. Genotoxic constituents are evaluated according to the methodology provided in the ICHM7 guideline. A Toxicological Reference Value (TRV) is associated to each non-genotoxic constituent, using one of the following methodologies (decision-tree successive steps): extraction from recognized databases or clinical studies, application of adequate safety factors to NOAELs established in animal studies, read-across analyses and when none was possible, TTC of Cramer classes. An EO recommended dose is considered safe when the safety margin (ratio between TRV and systemic exposure) for all constituents is all at least equal to 1. In conclusion, this methodology has proven to be robust to establish safe recommended doses for EOs used as food supplements, consistent with those publicly available, and avoiding unnecessary dedicated new animal testing.

Lobostemon trigonus (Thunb.) H. Buek, a medicinal plant from South Africa as a potential natural microbicide against HIV-1

ETHNOPHARMACOLOGICAL RELEVANCE

There have been different methods proposed to prevent the sexual transmission of HIV-1 and many of them have centered on the use of anti-retrovirals as microbicides. Given that a large section of the African population still relies on herbal medicine, Lobostemon trigonus (L. trigonus), a traditionally used medicinal plant in South Africa to treat HIV-1 was further investigated for its potential as a natural microbicide to prevent the sexual transmission of HIV-1.

METHODS

The aerial parts of L. trigonus were oven-dried at 80 °C, ground, extracted with boiling water for 30 min and then filtered. The aqueous extract produced was then bioassayed using different HIV-1 inhibition assays. The active components were purified and chemically profiled using ultra-performance liquid chromatography/quadrupole time-of flight mass spectrometry (UPLC-qTOF-MS). The mechanism of HIV-1 inhibition was determined by fusion arrest assay and time of addition assay. Molecular modelling and molecular dynamic simulations, using Schrödinger, were used to better understand the molecule's mechanism of entry inhibition by evaluating their docking affinity and stability against the gp120 of HIV-1.

RESULTS

The aqueous extract of this plant had a broad spectrum of activity against different subtypes of the virus; neutralizing subtype A, B and C in the TZM-bl cells, with IC₅₀ values ranging from 0.10 to 7.21 μg/mL. The extract was also inhibitory to the virus induced cytopathic effects in CEM-SS cells with an EC₅₀ of 8.9 μg/mL. In addition, it inhibited infection in peripheral blood mononuclear cells (PBMC) and macrophages with IC₅₀ values of 0.97 and 4.4 μg/mL, respectively. In the presence of vaginal and seminal simulants, and in human semen it retained its inhibitory activity albeit with a decrease in efficiency, by about 3-fold. Studies of the mode of action suggested that the extract blocked HIV-1 attachment to target cells. No toxicity was observed when the Lactobacilli strains, L. acidophilus, L. jensenii, and L. crispatus that populate the female genital tract were cultured in the presence of L. trigonus extract. UPLC-qTOF-MS analyses of the purified fraction of the extract, confirmed the presence of six compounds of which four were identified as rosmarinic acid, salvianolic acids B and C and lithospermic acid. The additional molecular dynamic simulations provided further insight into the entry inhibitory characteristics of salvianolic acid B against the HIV-1 gp120, with a stable pose being found within the CD4 binding site.

CONCLUSION

The data suggests that the inhibitory effect of L. trigonus may be due to the presence of organic acids which are known to possess anti-HIV-1 properties. The molecules salvianolic acids B and C have been identified for the first time in L. trigonus species. Our study also showed that the L. trigonus extract blocked HIV-1 attachment to target cells, and that it has a broad spectrum of activity against different subtypes of the virus; thus, justifying further investigation as a HIV-1 microbicide.

Coffee decoction enhances tamoxifen proapoptotic activity on MCF-7 cells

The consumption of coffee has been suggested to effectively enhance the therapeutic effects of tamoxifen against breast cancer; however, the underlying molecular mechanisms remain unclear. We herein attempted to clarify how coffee decoction exerts anti-cancer effects in cooperation with tamoxifen using the estrogen receptor α (ERα)-positive breast cancer cell line, MCF-7. The results obtained showed that coffee decoction down-regulated the expression of ERα, which was attributed to caffeine inhibiting its transcription. Coffee decoction cooperated with tamoxifen to induce cell-cycle arrest and apoptotic cell death, which may have been mediated by decreases in cyclin D1 expression and the activation of p53 tumor suppressor. The inclusion of caffeine in coffee decoction was essential, but not sufficient, to induce cell-cycle arrest and apoptotic cell death, suggesting the requirement of unknown compound(s) in coffee decoction to decrease cyclin D1 expression and activate apoptotic signaling cascades including p53. The activation of p53 through the cooperative effects of these unidentified component(s), caffeine, and tamoxifen appeared to be due to the suppression of the ERK and Akt pathways. Although the mechanisms by which the suppression of these pathways induces p53-mediated apoptotic cell death remain unclear, the combination of decaffeinated coffee, caffeine, and tamoxifen also caused cell-cycle arrest and apoptotic cell death, suggesting that unknown compound(s) present in decaffeinated coffee cooperate with caffeine and tamoxifen.

Reversal of Ovarian Cancer Cell Lines Multidrug Resistance Phenotype by the Association of Apiole with Chemotherapies

Multidrug resistance (MDR) is the main obstacle in anticancer therapy. The use of drug combinations to circumvent tumor resistance is a well-established principle in the clinic. Among the therapeutic targets, glycoprotein-P (P-gp), an energy-dependent transmembrane efflux pump responsible for modulating MDR, is highlighted. Many pharmacological studies report the ability of calcium channel blockers to reverse tumor resistance to chemotherapy drugs. Isolated for the first time from parsley, the phenylpropanoid apiole is described as a potent calcium channel inhibitor. Taking this into account, herein, the ability of apiole to potentiate the action of well-established chemotherapeutics in the clinic, as well as the compound’s relationship with the reversal of the resistance phenomenon by blocking P-gp, is reported. The association of apiole with both chemotherapeutic drugs doxorubicin and vincristine resulted in synergistic effect, in a concentration-dependent manner, as evaluated by the concentration reduction index. Molecular docking analysis demonstrated the affinity between apiole and the active site of P-gp, corroborating the inhibitory effect. Moreover, apiole demonstrated druglikeness, according to ADME analysis. In conclusion, apiole possibly blocks the active P-gp site, with strong binding energy, which, in turn, inhibits doxorubicin and vincristine efflux, increasing the antiproliferative response of these chemotherapeutic agents.

Genotoxicity assessment of saline extract from Pilosocereus gounellei (Cactaceae) and its chemopreventive effect against cyclophosphamide-induced DNA damage

Pilosocereus gounellei (Cactaceae) is used to treat wounds and inflammation. In this study, we evaluated whether the saline extract from its stem would have genotoxic or anti-genotoxic effects. In the genotoxicity evaluation, mice received the extract (500, 1,000, or 2,000 mg/kg) orally while negative and positive controls were treated with saline solution (0.9% NaCl) per os and cyclophosphamide (CPA, 80 mg/kg i.p.), respectively. In the anti-genotoxicity assay, using other animals, treatments were carried out by administering the extract (500, 1,000 or 2,000 mg/kg) or saline solution (negative control) per os and then CPA (80 mg/kg i.p.) 1 h later. Genotoxic effects were evaluated by micronucleus test and comet assay using peripheral blood and bone marrow cells. Oral administration of only the extract at 500 and 1,000 mg/kg did not result in genotoxicity. A slight increase in the incidence of micronucleus was observed at the highest dose (2,000 mg/kg). Administration of the extract before CPA reduced the micronucleated polychromatic erythrocytes (MNPCE) number by 49.07–71.43%, and DNA fragmentation in peripheral blood (85.04–94.44%) and bone marrow (87.43–92.70%) cells also decreased. In conclusion, when administered orally at the tested doses, the extract is genotoxically safe, being cautious in doses above 1,000 mg/kg, and has a protective effect against CPA-induced DNA damage.

Role of Metabolic Activation in Elemicin-Induced Cellular Toxicity

Elemicin, an alkenylbenzene constituent of natural oils of several plant species, is widely distributed in food, dietary supplements, and medicinal plants. 1'-Hydroxylation is known to cause metabolic activation of alkenylbenzenes leading to their potential toxicity. The aim of this study was to explore the relationship between elemicin metabolism and its toxicity through comparing the metabolic maps between elemicin and 1'-hydroxyelemicin. Elemicin was transformed into a reactive metabolite of 1'-hydroxyelemicin, which was subsequently conjugated with cysteine (Cys) and N-acetylcysteine (NAC). Administration of NAC could significantly ameliorate the elemicin- and 1'-hydroxyelemicin-induced cytotoxicity of HepG2 cells, while depletion of Cys with diethyl maleate (DEM) increased cytotoxicity. Recombinant human CYP screening and CYP inhibition experiments revealed that multiple CYPs, notably CYP1A1, CYP1A2, and CYP3A4, were responsible for the metabolic activation of elemicin. This study revealed that metabolic activation plays a critical role in elemicin cytotoxicity.

Future in the Past: Azorella glabra Wedd. as a Source of New Natural Compounds with Antiproliferative and Cytotoxic Activity on Multiple Myeloma Cells

Multiple myeloma (MM) is the second most common hematologic malignancy and, although the development of novel agents has improved survival of patients, to date, it remains incurable. Thus, newer and more effective therapeutic strategies against this malignancy are necessary. Plant extracts play an important role in anti-tumor drug discovery. For this reason, in the investigation of novel natural anti-MM agents, we evaluated the phytochemical profiles, in vitro antioxidant activity, and effects on MM cells of Azorella glabra (AG) Wedd. Total polyphenols (TPC), flavonoids (TFC), and terpenoids (TTeC) contents were different among samples and the richest fractions in polyphenols demonstrated a higher antioxidant activity in in vitro assays. Some fractions showed a dose and time dependent anti-proliferative activity on MM cells. The chloroform fraction (CHCl₃) showed major effects in terms of reduction of cell viability, induction of apoptosis, and cell cycle arrest on MM cells. The apoptosis induction was also confirmed by the activation of caspase-3. Importantly, the CHCl₃ fraction exhibited a negligible effect on the viability of healthy cells. These results encourage further investigations on AG extracts to identify specific bioactive compounds and to define their potential applications in MM.

Free radical scavenging, α-glucosidase inhibitory and lipase inhibitory activities of eighteen Sudanese medicinal plants

BACKGROUND

Lifestyle-related diseases such as diabetes are steadily increasing worldwide. In Sudan, there are a variety of plant species used traditionally for the treatment of diabetes, obesity and other symptoms which need to be validated through scientific studies for their claimed traditional uses. Therefore, in the current study, the free radical scavenging activity, α-glucosidase inhibitory and pancreatic lipase inhibitory activities of 70% ethanol and water extracts of eighteen Sudanese medicinal plants were investigated using various in vitro assays. Moreover, the cytotoxicity and genotoxicity were assessed for the bioactive plant extracts.

METHODS

Eighteen plants were selected on the basis of their traditional uses and extracted with 70% ethanol and water to obtain thirty-six extracts. The obtained extracts were screened using different in vitro bioassays namely, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, α-glucosidase inhibitory and pancreatic lipase inhibitory assays. Furthermore, the active plant extracts were investigated for their cytotoxicity and genotoxicity on HeLa cell line using HCS DNA Damage Assay.

RESULTS

Both 70% ethanol and water extracts of Acacia nilotica, Ziziphus spina-christi, Abrus precatorius, and Geigeria alata along with the 70% ethanol extract of Martynia annua showed potent free radical scavenging activity. Regarding the α-glucosidase inhibition assay, both extracts of Acacia nilotica, Ziziphus spina-christi, Geigeria alata, and Cyperus rotundus showed potent activity. In general, 70% ethanol extracts were more potent compared to water extracts with exception of Cordia sinensis and Cymbopogon proximus, for which water extracts also showed potent enzyme inhibitory activity. Similarly, water extracts of Acacia nilotica and Ziziphus spina-christi showed potent inhibitory activity against pancreatic lipase enzyme. Some of the extracts also showed significant genotoxicity and cytotoxicity at the concentration range used for bioactivities.

CONCLUSION

The extracts of Acacia nilotica, Ziziphus spina-christi, Geigeria alata, Martynia annua and Abrus precatorius exhibited an appreciable range of activity on antioxidant and enzyme inhibitory assays.

The Current Status of the Pharmaceutical Potential of Juniperus L. Metabolites

Background: Plants and their derived natural compounds possess various biological and therapeutic properties, which turns them into an increasing topic of interest and research. Juniperus genus is diverse in species, with several traditional medicines reported, and rich in natural compounds with potential for development of new drugs. Methods: The research for this review were based in the Scopus and Web of Science databases using terms combining Juniperus, secondary metabolites names, and biological activities. This is not an exhaustive review of Juniperus compounds with biological activities, but rather a critical selection taking into account the following criteria: (i) studies involving the most recent methodologies for quantitative evaluation of biological activities; and (ii) the compounds with the highest number of studies published in the last four years. Results: From Juniperus species, several diterpenes, flavonoids, and one lignan were emphasized taking into account their level of activity against several targets. Antitumor activity is by far the most studied, being followed by antibacterial and antiviral activities. Deoxypodophyllotoxin and one dehydroabietic acid derivative appears to be the most promising lead compounds. Conclusions: This review demonstrates the Juniperus species value as a source of secondary metabolites with relevant pharmaceutical potential.