Naturally occurring aristolactams, aristolochic acids and dioxoaporphines and their biological activities

Inhibitors and activators for myotoxic phospholipase A2-like toxins from snake venoms - A structural overview

Snakebite envenomations result in acute and chronic physical and psychological health effects on their victims, leading to a substantial socio-economic burden in tropical and subtropical countries. Local necrosis is one of the serious effects caused by envenomation, primarily induced by snake venoms from the Viperidae family through the direct action of components collectively denominated as myotoxins, including the phopholipase A2-like (PLA2-like) toxins. Considering the limitations of antivenoms in preventing the rapid development of local tissue damage caused by envenomation, the use of small molecule therapeutics has been suggested as potential first-aid treatments or as adjuvants to antivenom therapy. In this review, we provide an overview of the structural interactions of molecules exhibiting inhibitory activity toward PLA2-like toxins. Additionally, we discuss the implications for the myotoxic mechanism of PLA2-like toxins and the molecules involved in their activation, highlighting key differences between activators and inhibitors. Finally, we integrate all these results to propose a classification of inhibitors into three different classes and five sub-classes. Taking into account the structural and affinity information, we compare the different inhibitors/ligands to gain a deeper understanding of the structural basis for the effective inhibition of PLA2-like toxins. By offering these insights, we aim to contribute to the search for new and efficient inhibitor molecules to complement and improve current therapy by conventional antivenoms.

Bis(aminoalkyl)cyclopropenylidene (BAC)-Catalyzed Intramolecular Annulation of 2-(2-Formylaryl)-aryl-Substituted p-Quinone Methides to 9-Phenanthrol Derivatives

This article describes a bis(aminoalkyl)cyclopropenylidene (BAC)-catalyzed intramolecular annulation of strategically designed 2-(2-formylaryl)-phenyl-substituted p-quinone methides (p-QMs) to access 9-phenanthrol derivatives and related carbocycles. In addition, the synthetic utility of this methodology has been demonstrated in the synthesis of the seven-membered carbocyclic core of resveratrol-based natural products (±)-shoreaphenol and (±)-malibatol A.

Natural aporphine alkaloids: A comprehensive review of phytochemistry, pharmacokinetics, anticancer activities, and clinical application

BACKGROUND

Cancer is the most common cause of death and is still a serious public health problem. Alkaloids, a class of bioactive compounds widely diffused in plants, especially Chinese herbs, are used as functional ingredients, precursors, and lead compounds in food and clinical applications. Among them, aporphine alkaloids (AAs), as an important class of isoquinoline alkaloids, exert a strong anticancer effect on multiple cancer types.

AIM OF REVIEW

This review aims to comprehensively summarize the phytochemistry, pharmacokinetics, and bioavailability of seven subtypes of AAs and their derivatives from various plants and highlight their anticancer bioactivities and mechanisms of action. Key Scientific Concepts of Review. The chemical structures and botanical diversity of AAs are elucidated, and promising results are highlighted regarding the potent anticancer activities of AAs and their derivatives, contributing to their pharmacological benefits. This work provides a better understanding of AAs and combinational anticancer therapies involving them, thereby improving the development of functional food containing plant-derived AA and the clinical application of AAs.

Structural and mechanistic insights into the transport of aristolochic acids and their active metabolites by human serum albumin

Aristolochic acids I and II (AA-I/II) are carcinogenic principles of Aristolochia plants, which have been employed in traditional medicinal practices and discovered as food contaminants. While the deleterious effects of AAs are broadly acknowledged, there is a dearth of information to define the mechanisms underlying their carcinogenicity. Following bioactivation in the liver, N-hydroxyaristolactam and N-sulfonyloxyaristolactam metabolites are transported via circulation and elicit carcinogenic effects by reacting with cellular DNA. In this study, we apply DNA adduct analysis, X-ray crystallography, isothermal titration calorimetry, and fluorescence quenching to investigate the role of human serum albumin (HSA) in modulating AA carcinogenicity. We find that HSA extends the half-life and reactivity of N-sulfonyloxyaristolactam-I with DNA, thereby protecting activated AAs from heterolysis. Applying novel pooled plasma HSA crystallization methods, we report high-resolution structures of myristic acid-enriched HSA (HSAMYR) and its AA complexes (HSAMYR/AA-I and HSAMYR/AA-II) at 1.9 Å resolution. While AA-I is located within HSA subdomain IB, AA-II occupies subdomains IIA and IB. ITC binding profiles reveal two distinct AA sites in both complexes with association constants of 1.5 and 0.5 · 106 M-1 for HSA/AA-I versus 8.4 and 9.0 · 105 M-1 for HSA/AA-II. Fluorescence quenching of the HSA Trp214 suggests variable impacts of fatty acids on ligand binding affinities. Collectively, our structural and thermodynamic characterizations yield significant insights into AA binding, transport, toxicity, and potential allostery, critical determinants for elucidating the mechanistic roles of HSA in modulating AA carcinogenicity.

Human UDP-glucuronosyltransferase 1As catalyze aristolochic acid D O-glucuronidation to form a lesser nephrotoxic glucuronide

ETHNOPHARMACOLOGICAL RELEVANCE

Aristolochic acids (AAs) are naturally occurring nitro phenanthrene carboxylic acids primarily found in plants of the Aristolochiaceae family. Aristolochic acid D (AAD) is a major constituent in the roots and rhizomes of the Chinese herb Xixin (the roots and rhizomes of Asarum heterotropoides F. Schmidt), which is a key material for preparing a suite of marketed Chinese medicines. Structurally, AAD is nearly identical to the nephrotoxic aristolochic acid I (AAI), with an additional phenolic group at the C-6 site. Although the nephrotoxicity and metabolic pathways of AAI have been well-investigated, the metabolic pathway(s) of AAD in humans and the influence of AAD metabolism on its nephrotoxicity has not been investigated yet.

AIM OF THE STUDY

To identify the major metabolites of AAD in human tissues and to characterize AAD O-glucuronidation kinetics in different enzyme sources, as well as to explore the influence of AAD O-glucuronidation on its nephrotoxicity.

MATERIALS AND METHODS

The O-glucuronide of AAD was biosynthesized and its chemical structure was fully characterized by both 1H-NMR and 13C-NMR. Reaction phenotyping assays, chemical inhibition assays, and enzyme kinetics analyses were conducted to assess the crucial enzymes involved in AAD O-glucuronidation in humans. Docking simulations were performed to mimic the catalytic conformations of AAD in human UDP-glucuronosyltransferases (UGTs), while the predicted binding energies and distances between the deprotonated C-6 phenolic group of AAD and the glucuronyl moiety of UDPGA in each tested human UGT isoenzyme were measured. The mitochondrial membrane potentials (MMP) and reactive oxygen species (ROS) levels in HK-2 cells treated with either AAI, or AAD, or AAD O-glucuronide were tested, to elucidate the impact of O-glucuronidation on the nephrotoxicity of AAD.

RESULTS

AAD could be rapidly metabolized in human liver and intestinal microsomes (HLM and HIM, respectively) to form a mono-glucuronide, which was purified and fully characterized as AAD-6-O-β-D-glucuronide (AADG) by NMR. UGT1A1 was the predominant enzyme responsible for AAD-6-O-glucuronidation, while UGT1A9 contributed to a lesser extent. AAD-6-O-glucuronidation in HLM, HIM, UGT1A1 and UGT1A9 followed Michaelis-Menten kinetics, with the Km values of 4.27 μM, 9.05 μM, 3.87 μM, and 7.00 μM, respectively. Docking simulations suggested that AAD was accessible to the catalytic cavity of UGT1A1 or UGT1A9 and formed catalytic conformations. Further investigations showed that both AAI and AAD could trigger the elevated intracellular ROS levels and induce mitochondrial dysfunction and in HK-2 cells, but AADG was hardly to trigger ROS accumulation and mitochondrial dysfunction.

CONCLUSION

Collectively, UGT1A-catalyzed AAD 6-O-glucuronidation represents a crucial detoxification pathway of this naturally occurring AAI analogs in humans, which is very different from that of AAI.

Structural variety and pharmacological potential of naphthylisoquinoline alkaloids

Naphthylisoquinoline alkaloids are a fascinating class of natural biaryl compounds. They show characteristic mono- and dimeric scaffolds, with chiral axes and stereogenic centers. Since the appearance of the last comprehensive overview on these secondary plant metabolites in this series in 1995, the number of discovered representatives has tremendously increased to more than 280 examples known today. Many novel-type compounds have meanwhile been discovered, among them naphthylisoquinoline-related follow-up products like e.g., the first seco-type (i.e., ring-opened) and ring-contracted analogues. As highlighted in this review, the knowledge on the broad structural chemodiversity of naphthylisoquinoline alkaloids has been decisively driven forward by extensive phytochemical studies on the metabolite pattern of Ancistrocladus abbreviatus from Coastal West Africa, which is a particularly "creative" plant. These investigations furnished a considerable number of more than 80-mostly new-natural products from this single species, with promising antiplasmodial activities and with pronounced cytotoxic effects against human leukemia, pancreatic, cervical, and breast cancer cells. Another unique feature of naphthylisoquinoline alkaloids is their unprecedented biosynthetic origin from polyketidic precursors and not, as usual for isoquinoline alkaloids, from aromatic amino acids-a striking example of biosynthetic convergence in nature. Furthermore, remarkable botanical results are presented on the natural producers of naphthylisoquinoline alkaloids, the paleotropical Dioncophyllaceae and Ancistrocladaceae lianas, including first investigations on the chemoecological role of these plant metabolites and their storage and accumulation in particular plant organs.

Steroids Bearing Heteroatom as Potential Drugs for Medicine

Heteroatom steroids, a diverse class of organic compounds, have attracted significant attention in the field of medicinal chemistry and drug discovery. The biological profiles of heteroatom steroids are of considerable interest to chemists, biologists, pharmacologists, and the pharmaceutical industry. These compounds have shown promise as potential therapeutic agents in the treatment of various diseases, such as cancer, infectious diseases, cardiovascular disorders, and neurodegenerative conditions. Moreover, the incorporation of heteroatoms has led to the development of targeted drug delivery systems, prodrugs, and other innovative pharmaceutical approaches. Heteroatom steroids represent a fascinating area of research, bridging the fields of organic chemistry, medicinal chemistry, and pharmacology. The exploration of their chemical diversity and biological activities holds promise for the discovery of novel drug candidates and the development of more effective and targeted treatments.

Characterization of two putative norlaudanosoline methyltransferases from Aristolochia debilis

In view of the nephrotoxicity, hepatotoxicity, and carcinogenicity of aristolochic acids (AAs), the removal of AAs from plants becomes an urgent priority for ensuring the safety of Aristolochia herbal materials. In this study, based on the root-predominant distribution of aristolochic acid I (AAI) in Aristolochia debilis, transcriptome sequencing, in combination with phylogenetic analyses, and gene expression pattern analysis together provided five candidate genes for investigating AAI biosynthesis. Comprehensive in vitro and in vivo enzymatic assays revealed that Ab6OMT1 (6-O-methyltransferase) and AbNMT1 (N-methyltransferase) exhibit promiscuity in substrate recognition, and they could act in a cooperative fashion to achieve conversion of norlaudanosoline, a predicted intermediate in AAI biosynthetic route, into 3'-hydroxy-N-methylcoclaurine through two different methylation reaction sequences. These results shed light on the molecular basis for AAI biosynthesis in Aristolochia herbs. More importantly, Ab6OMT1 and AbNMT1 may be employed as targets for the metabolic engineering of AAI biosynthesis to produce AAs-free Aristolochia herbal materials.

Differences in p38-STAT3-S100A11 signaling after the administration of aristolochic acid I and IVa may account for the disparity in their nephrotoxicity

BACKGROUND

The safety of herbs containing aristolochic acids (AAs) has become a widespread concern. Previous reports indicate that AAs are highly nephrotoxic and carcinogenic, although there are more than 170 analogues of aristolochic acid. Not all AAs have the same degree of nephrotoxicity or carcinogenicity. Previous studies have found that aristolochic acid IVa (AA-IVa), the principal component of AAs within members of the Aristolochiaceae family, especially Asarum, a commonly used herb in China, has essentially no significant nephrotoxicity. However, several studies, including ours, have shown that aristolochic acid I (AA-I) is clearly nephrotoxic.

PURPOSE

The focus of the study was to elucidate the molecular mechanism responsible for the difference in nephrotoxicity between the AA-I and AA-IVa.

STUDY DESIGN/METHOD

Mice were administered with AA-I or AA-IVa for 22 weeks through the oral route, followed by a 50-week recovery time. The kidney tissues of mice were extracted at the end of 22 weeks. Pathological examination and proteomic detection (tandem mass tagging (TMT) and phosphorylated proteomics) were performed on the kidney tissue to investigate the key signaling pathways and targets of AAs-induced renal interstitial fibrosis (RIF). The key signaling pathways and targets were verified by Western blot (WB), siRNA transfection, and luciferase assays.

RESULTS

AA-I caused severe nephrotoxicity, high mortality, and extensive RIF. However, the same AA-IVa dosage exhibited almost no nephrotoxicity and does not trigger RIF. The activation of the p38-STAT3-S100A11 signaling pathway and upregulated expression of α smooth muscle actin (α-SMA) and Bcl2-associated agonist of cell death (Bad) proteins could be the molecular mechanism underlying AA-I-induced nephrotoxicity. On the other hand, AA-IVa did not regulate the activation of the p38-STAT3-S100A11 signaling pathway and had relatively little effect on the expression of α-SMA and Bad. Consequently, the difference in the regulation of p38-STAT3-S100A11 pathway, α-SMA, and Bad proteins between AA-I and AA-IVa may be responsible for the divergence in their level of nephrotoxicity.

CONCLUSION

This is the first study to reveal the molecular mechanism underlying the difference in nephrotoxicity between AA-I and AA-IVa. Whether STAT3 is activated or not may be the key factor leading to the difference in nephrotoxicity between AA-I and AA-IVa.

Mode of action, chemistry and defensive efficacy of the osmeterium in the caterpillar Battus polydamas archidamas

Chemical secretions are one of the main defensive mechanisms in insects. The osmeterium is a unique organ in larvae of Papilionidae (Lepidoptera), which is everted upon disturbance, secreting odoriferous volatiles. Here, using larvae of the specialized butterfly Battus polydamas archidamas (Papilionidae: Troidini), we aimed to understand the mode of action of the osmeterium, the chemical composition and origin of the secretion, as well as its defensive efficiency against a natural predator. We described osmeterium's morphology, ultramorphology, structure, ultrastructure, and chemistry. Additionally, behavioral assays of the osmeterial secretion against a predator were developed. We showed that the osmeterium is composed of tubular arms (made up by epidermal cells) and of two ellipsoid glands, which possess a secretory function. The eversion and retraction of the osmeterium are dependent on the internal pressure generated by the hemolymph, and by longitudinal muscles that connect the abdomen with the apex of the osmeterium. Germacrene A was the main compound present in the secretion. Minor monoterpenes (sabinene and ß-pinene) and sesquiterpenes ((E)-β-caryophyllene, selina-3,7(11)-diene, and other some unidentified compounds) were also detected. Only sesquiterpenes (with the exception of (E)-β-caryophyllene) are likely to be synthesized in the osmeterium-associated glands. Furthermore, the osmeterial secretion proved to deter predatory ants. Our results suggest that the osmeterium, besides serving as an aposematic warning for enemies, is an efficient chemical defense, with its own synthesis of irritant volatiles.

Non-carcinogenic/non-nephrotoxic aristolochic acid IVa exhibited anti-inflammatory activities in mice

Aristolochic acid (AA)-containing herbs have been prescribed for thousands of years as anti-inflammatory drugs, despite the active pharmaceutical ingredients remaining unclear. However, exposure to AAI and AAII has been proven to be a significant risk factor for severe nephropathy and carcinogenicity. AAIVa, an analogue abundant in AA-containing herbs, showed neither carcinogenicity nor nephrotoxicity in our study and other reports, implying that the pharmacological effects of AAIVa on inflammation are worth studying. Herein, we employed RAW 264.7 cells, the ear edema mouse model, and the lipopolysaccharide (LPS)-induced systematic inflammation model in TNF-IRES-Luc mice (tracking TNFα luciferase activities in real-time) to evaluate the anti-inframammary effect of AAIVa. Our results showed that AAIVa could decrease pro-inflammatory cytokines (TNFα and IL-6) production in LPS-stimulated RAW 264.7 cells, indicating its anti-inflammatory effects in vitro. Furthermore, the application of AAIVa (400 and 600 μg/ear) could significantly inhibit phorbol 12-myristate 13-acetate-induced ear edema, suggesting its topical anti-inflammatory activity in vivo. Moreover, LPS-stimulated TNF-IRES-Luc mice were used to investigate the onset and duration of AAIVa on systematic inflammation. A single dosage of AAIVa (100 mg/kg, i.g.) could suppress LPS-triggered inflammation, by decreasing luciferase activities of TNFα at 3 h in TNF-IRES-Luc mice. In addition, the online pharmacological databases predicted that AAIVa might target the regulation of T cell activation-related protein (ADA, ADORA2A, ERBB2) to exhibit anti-inflammatory effect. In conclusion, we demonstrated that AAIVa had anti-inflammatory effect for the first time; our findings are constructive for further studies on pharmacological mechanism of AAIVa.

Comparative Analysis of Aristolochic Acids in Aristolochia Medicinal Herbs and Evaluation of Their Toxicities

Aristolochic acids (AAs) are a group of nitrophenanthrene carboxylic acids present in many medicinal herbs of the Aristolochia genus that may cause irreversible hepatotoxicity, nephrotoxicity, genotoxicity and carcinogenicity. However, the specific profile of AAs and their toxicity in Aristolochia plants, except for AAs Ι and ΙΙ, still remain unclear. In this study, a total of 52 batches of three medicinal herbs belonging to the Aristolochia family were analyzed for their AA composition profiles and AA contents using the UPLC-QTOF-MS/MS approach. The studied herbs were A. mollissima Hance (AMH), A. debilis Sieb.etZucc (ADS), and A. cinnabaria C.Y.Cheng (ACY). Chemometrics methods, including PCA and OPLS-DA, were used for the evaluation of the Aristolochia medicinal herbs. Additionally, cytotoxicity and genotoxicity of the selected AAs and the extracts of AMH and ADS were evaluated in a HepG2 cell line using the MTT method and a Comet assay, respectively. A total of 44 AAs, including 23 aristolochic acids and 21 aristolactams (ALs), were detected in A. mollissima. Moreover, 41 AAs (23 AAs and 18 ALs) were identified from A. debilis Sieb, and 45 AAs (29 AAs and 16 ALs) were identified in A. cinnabaria. Chemometrics results showed that 16, 19, and 22 AAs identified in AMH, ADS, and ACY, respectively, had statistical significance for distinguishing the three medicinal herbs of different origins. In the cytotoxicity assay, compounds AL-BΙΙ, AAΙ and the extract of AMH exhibited significant cytotoxicities against the HepG2 cell line with the IC₅₀ values of 0.2, 9.7 and 50.2 μM, respectively. The results of the Comet assay showed that AAΙ caused relatively higher damage to cellular DNA (TDNA 40-95%) at 50 μM, while AAΙΙ, AMH and ADS extracts (ranged from 10 to 131 μM) caused relatively lower damage to cellular DNA (TDNA 5-20%).

Naphthylisoindolinone alkaloids: the first ring-contracted naphthylisoquinolines, from the tropical liana Ancistrocladus abbreviatus, with cytotoxic activity

The West African liana Ancistrocladus abbreviatus is a rich source of structurally most diverse naphthylisoquinoline alkaloids. From its roots, a series of four novel representatives, named ancistrobrevolines A-D (14-17) have now been isolated, displaying an unprecedented heterocyclic ring system, where the usual isoquinoline entity is replaced by a ring-contracted isoindolinone part. Their constitutions were elucidated by 1D and 2D NMR and HR-ESI-MS. The absolute configurations at the chiral axis and at the stereogenic center were assigned by using experimental and computational electronic circular dichroism (ECD) investigations and a ruthenium-mediated oxidative degradation, respectively. For the biosynthetic origin of the isoindolinones from 'normal' naphthyltetrahydroisoquinolines, a hypothetic pathway is presented. It involves oxidative decarboxylation steps leading to a ring contraction by a benzilic acid rearrangement. Ancistrobrevolines A (14) and B (15) were found to display moderate cytotoxic effects (up to 72%) against MCF-7 breast and A549 lung cancer cells and to reduce the formation of spheroids (mammospheres) in the breast cancer cell line.

Aristolochic acid-associated cancers: a public health risk in need of global action

Aristolochic acids (AAs) are a group of naturally occurring compounds present in many plant species of the Aristolochiaceae family. Exposure to AA is a significant risk factor for severe nephropathy, and urological and hepatobiliary cancers (among others) that are often recurrent and characterized by the prominent mutational fingerprint of AA. However, herbal medicinal products that contain AA continue to be manufactured and marketed worldwide with inadequate regulation, and possible environmental exposure routes receive little attention. As the trade of food and dietary supplements becomes increasingly globalized, we propose that further inaction on curtailing AA exposure will have far-reaching negative effects on the disease trends of AA-associated cancers. Our Review aims to systematically present the historical and current evidence for the mutagenicity and carcinogenicity of AA, and the effect of removing sources of AA exposure on cancer incidence trends. We discuss the persisting challenges of assessing the scale of AA-related carcinogenicity, and the obstacles that must be overcome in curbing AA exposure and preventing associated cancers. Overall, this Review aims to strengthen the case for the implementation of prevention measures against AA's multifaceted, detrimental and potentially fully preventable effects on human cancer development.

Nephrotoxicity induced by natural compounds from herbal medicines - a challenge for clinical application

Herbal medicines (HMs) have long been considered safe and effective without serious toxic and side effects. With the continuous use of HMs, more and more attention has been paid to adverse reactions and toxic events, especially the nephrotoxicity caused by natural compounds in HMs. The composition of HMs is complex and various, especially the mechanism of toxic components has been a difficult and hot topic. This review comprehensively summarizes the kidney toxicity characterization and mechanism of nephrotoxic natural compounds (organic acids, alkaloids, glycosides, terpenoids, phenylpropanoids, flavonoids, anthraquinones, cytotoxic proteins, and minerals) from different sources. Recommendations for the prevention and treatment of HMs-induced kidney injury were provided. In vitro and in vivo models for evaluating nephrotoxicity and the latest biomarkers are also included in this investigation. More broadly, this review may provide theoretical basis for safety evaluation and further comprehensive development and utilization of HMs in the future.

Aristolochic Acid Nephropathy: A Novel Suppression Strategy of Carbon Dots Derived from Astragali Radix Carbonisata

Despite strict restrictions on the use of aristolochic acids (AAs)-containing merchandise or drugs in many countries, a substantial amounts of occurrences aristolochic acid nephropathy (AAN) had been accounted worldwide. Clinically, there is no effective incurable therapy regimen to reverse the progression of AAN. Although carbon dots have shown surprising bioactivity, research on the acute kidney injury caused by AAs is lacking. Here, a novel biomass-carbon dots from Astragali Radix (AR) as precursors was synthesized through one-step pyrolysis treatment. The ARC-carbon dots (ARC-CDs) was demonstrated in detail for its inhibitory effect on aristolochic acid nephropathy in a mice model. The indexes of inflammatory cytokines as well as oxidative stress were significantly reduced by the ARC-CDs in kidney tissue cells. Additionally, the ARC-CDs administration resulted in a large decrease in positive apoptotic cells according to TUNEL labeling and western blotting, which may be connected to the ARC-CDs’ modulation of the protein in the Akt/Mdm2/p53 signaling pathway. These findings show that ARC-CDs have remarkable anti-inflammatory, antioxidant, and anti-apoptotic capabilities against acute kidney injury spurred by aristolochic acids via the AKT/Mdm2/p53 signaling pathway.

Electrochemical C(sp3)-H Functionalization of γ-Lactams Based on Hydrogen Atom Transfer

We describe the electrochemical α-amidoalkylation of γ-lactams based on transition-metal-free cross-coupling via hydrogen atom transfer. The highly selective hydrogen atom transfer process allows for a broad substrate scope including both inter- and intramolecular reactions. Also, the construction of quaternary centers was realized by a double hydrogen atom transfer protocol to afford spirocycles. Detailed mechanistic studies including experimental and computational studies are provided to support the reaction pathway.

Aristolochic acid I as an emerging biogenic contaminant involved in chronic kidney diseases: A comprehensive review on exposure pathways, environmental health issues and future challenges

Described in the 1950s, Balkan Endemic Nephropathy (BEN) has been recognized as a chronic kidney disease (CKD) with clinical peculiarities and multiple etiological factors. Environmental contaminants - aromatic compounds, mycotoxins and phytotoxins like aristolochic acids (AAs) - polluting food and drinking water sources, were incriminated in BEN, due to their nephrotoxic and carcinogenic properties. The implication of AAs in BEN etiology is currently a highly debated topic due to the fact that they are found within the Aristolochiaceae plants family, used around the globe as traditional medicine and they were also incriminated in Aristolochic Acid Nephropathy (AAN). Exposure pathways have been investigated, but it is unclear to what extent AAs are acting alone or in synergy with other cofactors (environmental, genetics) in triggering kidney damage. Experimental studies strengthen the hypothesis that AAI, the most studied compound in the AAs class, is a significant environmental contaminant and a most important causative factor of BEN. The aim of this review is to compile information about the natural exposure pathways to AAI, via traditional medicinal plants, soil, crop plants, water, food, air. Data that either supports or contradicts the AAI theory concerning BEN etiology was consolidated and available solutions to reduce human exposure were discussed. Because AAI is a phytotoxin with physicochemical properties that allow its transportation in environmental matrices from different types of areas (endemic, nonendemic), and induce CKDs (BEN, AAN) and urinary cancers through bioaccumulation, this review aims to shed a new light on this compound as a biogenic emerging pollutant.

Transition metal-free advanced synthetic approaches for isoindolinones and their fused analogues

The transition metal-free synthetic protocols of isoindolinone and its fused analogues are highlighted in this review since 2007 to 2021.

Phenanthrene Derivatives from Asarum heterotropoides Showed Excellent Antibacterial Activity against Phytopathogenic Bacteria

Asarum heterotropoides extracts showed strong antibacterial activity against selected phytopathogenic bacteria. Bioguided isolation was conducted to obtain 11 phenanthrene derivatives (1-11), 4 phenylpropanoids (12-15), a flavonoid (16), and a steroid (17), including a new phenanthrene derivative (1). In vitro bioassay results showed that phenanthrene derivatives are the main active components of A. heterotropoides extracts. The new compound aristoloxazine C (1) was found to exhibit outstanding antibacterial activity against Ralstonia solanacearum, Xanthomonas oryzae, Erwinia carolovora, Pseudomonas syringae, and Xanthomonas axonopodis, with MIC values of 0.05, 2.5, 2.5, 5, and 6.25 μg/mL, respectively. These values were significantly higher than that of the positive control, streptomycin sulfate. Aristoloxazine C (1) also demonstrated an excellent control effect on tobacco bacterial wilt. Physiological and biochemical experiments combined with electron microscopy showed that the antibacterial activity of aristoloxazine C (1) was primarily related to the destruction of the bacterial cell wall structure. Thus, aristoloxazine C (1) may have the potential to be used as a template for the development of new bactericides or as a probe for the discovery of new antimicrobial targets.

Aristolactam BIII, a naturally derived DYRK1A inhibitor, rescues Down syndrome-related phenotypes

BACKGROUND

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a significant pathogenic factor in Down syndrome (DS), wherein DYRK1A is overexpressed by 1.5-fold because of trisomy of human chromosome 21. Thus, DYRK1A inhibition is considered a therapeutic strategy to modify the disease.

PURPOSE

This study aims to identify a novel DYRK1A inhibitor and validate its therapeutic potential in DS-related pathological conditions.

STUDY DESIGN

In order to identify a novel DYRK1A inhibitor, we carried out two-step screening: a structure-based virtual screening of > 300,000 chemical library (first step) and cell-based nuclear factor of activated T-cells (NFAT)-response element (RE) promoter assay (second step). Primary hits were evaluated for their DYRK1A inhibitory activity using in vitro kinase assay and Tau phosphorylation in mammalian cells. Confirmed hit was further evaluated in pathological conditions including DYRK1A-overexpressing fibroblasts, flies, and mice.

RESULTS

We identified aristolactam BIII, a natural product derived from herbal plants, as a novel DYRK1A inhibitor. It potently inhibited the kinase activity of DYRK1A in vitro (IC₅₀ = 9.67 nM) and effectively suppressed DYRK1A-mediated hyperphosphorylation of Tau in mammalian cells. Aristolactam BIII rescued the proliferative defects of DYRK1A transgenic (TG) mouse-derived fibroblasts and neurological and phenotypic defects of DS-like Drosophila models. Oral administration of aristolactam BIII acutely suppressed Tau hyperphosphorylation in the brain of DYRK1A TG mice. In the open field test, aristolactam BIII significantly ameliorated the exploratory behavioral deficit of DYRK1A TG mice.

CONCLUSION

Our work revealed that aristolactam BIII as a novel DYRK1A inhibitor rescues DS phenotypes in cells and in vivo and suggested its therapeutic potential for the treatment of DYRK1A-related diseases.

1,3-Aza-Brook Rearrangement of Aniline Derivatives: In Situ Generation of 3-Aminoaryne via 1,3-C-(sp2)-to-N Silyl Migration

The design, synthesis, and validation of 3-aminobenzyne precursors induced by C-(sp²)-to-N 1,3-aza-Brook rearrangement have been achieved, allowing access to diverse aniline derivatives. Through crossover experiments, we demonstrated the intramolecular mechanism of 1,3-C-to-N silyl transfer. To gain insight into the regioselectivity observed in the reactions, we performed density functional theory calculations. Finally, the method was applied to the synthesis of xylanigripones A in five linear steps in an overall yield of 30%.

Co-Exposure to Aristolochic Acids I and II Increases DNA Adduct Formation Responsible for Aristolochic Acid I-Mediated Carcinogenicity in Rats

The plant extract aristolochic acid (AA), containing aristolochic acids I (AAI) and II (AAII) as major components, causes aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN), unique renal diseases associated with upper urothelial cancer. Recently (Chemical Research in Toxicology 33(11), 2804–2818, 2020), we showed that the in vivo metabolism of AAI and AAII in Wistar rats is influenced by their co-exposure (i.e., AAI/AAII mixture). Using the same rat model, we investigated how exposure to the AAI/AAII mixture can influence AAI and AAII DNA adduct formation (i.e., AA-mediated genotoxicity). Using ³²P-postlabelling, we found that AA-DNA adduct formation was increased in the livers and kidneys of rats treated with AAI/AAII mixture compared to rats treated with AAI or AAII alone. Measuring the activity of enzymes involved in AA metabolism, we showed that enhanced AA-DNA adduct formation might be caused partially by both decreased AAI detoxification as a result of hepatic CYP2C11 inhibition during treatment with AAI/AAII mixture and by hepatic or renal NQO1 induction, the key enzyme predominantly activating AA to DNA adducts. Moreover, our results indicate that AAII might act as an inhibitor of AAI detoxification in vivo. Consequently, higher amounts of AAI might remain in liver and kidney tissues, which can be reductively activated, resulting in enhanced AAI DNA adduct formation. Collectively, these results indicate that AAII present in the plant extract AA enhances the genotoxic properties of AAI (i.e., AAI DNA adduct formation). As patients suffering from AAN and BEN are always exposed to the plant extract (i.e., AAI/AAII mixture), our findings are crucial to better understanding host factors critical for AAN- and BEN-associated urothelial malignancy.

Computational Analysis of Naturally Occurring Aristolochic Acid Analogues and Their Biological Sources

Aristolochic acids are known for nephrotoxicity, and implicated in multiple cancer types such as hepatocellular carcinomas demonstrated by recent studies. Natural products that are analogues to aristolochic acids have been constantly isolated from organisms; a larger chemical space of these compounds and a wider coverage of biological sources should be determined in consideration of the potential hazard of aristolochic acid analogues and the wide distribution of their biological sources in the nature. Therefore, we carried out an in silico research of naturally occurring aristolochic acid analogues and their biological sources, as a supplement to existing studies. The result shows a chemical space of 238 naturally occurring aristolochic acid analogues that are present in 175 species of biological sources including 44 traditional medicines. With the computational estimation for toxicity and the implication in hazard assessment of a biological source with the presence of aristolochic acid analogues, we propose that additional awareness should be raised to the public for avoidance of toxic species, especially those that are used as herbal medicines and easily accessible.

Study on the potential nephrotoxicity and mutagenicity of aristolochic acid IVa and its mechanism

Previous reports demonstrated that aristolochic acids (AAs) exposure-induced nephrotoxicity, mutations, and tumorigenesis are mainly due to aristolochic acid I (AAI). Notably, the chemical structure of aristolochic acid IVa (AAIVa), which exists at higher levels in many Aristolochiaceae herbs, is extremely similar to AAI. In lack of toxicological data, it is unknown whether AAIVa exposure leads to aristolochic acid nephropathy (AAN), mutations, and tumorigenesis as of AAI. To answer these questions, mice were administered AAIVa by single or repeated long-term gavage, while AAI was used as a positive control. We found that single gavage of 40 mg/kg of AAIVa exhibited no obvious toxicity. Also, there were no tumors or death in mice administrated with 1 and 10 mg/kg of AAIVa for 6 months followed by a 12-month recovery time. There were no noteworthy alterations in gene mutation frequency in the kidney, liver, and stomach between the AAIVa and control mice. Fascinatingly, AA-associated mutational signatures, adenine-to-thymine (A>T) transversions, were absent in AAIVa-treated mice. Nonetheless, 10 mg/kg of AAIVa triggered lymphocytic infiltration and slight fibrous hyperplasia in the kidney at the 6^th month; however, these were alleviated at the 12^th and 18^th months. On the contrary, AAI (positive control) caused severe diffuse fibrosis, tubular atrophy, necrosis, tumors in the forestomach and kidney, and death after the 6^th month. It seems that long-term AAIVa exposure induced mild renal lesions could be due to the activation of the canonical or noncanonical transforming growth factor-β (TGFβ) pathway. Overall, these findings suggest that the mutagenicity and carcinogenic risk of AAIVa are very low.

Risk characterisation of constituents present in jamu to promote its safe use

Safety in use of jamu consumption, as part of traditional medicine from Indonesia, is dependent on the complete and adequate assessment of potential hazards and risks of the botanicals and botanical constituents included. This includes especially hazards and risks related to the presence in jamu of active pharmaceutical ingredients (APIs) as well as of constituents that are genotoxic and carcinogenic. The present review presents an overview of the current state-of-the art on these hazards and risks based on case reports on adulteration, and the actual detection of genotoxic and carcinogenic ingredients of concern in jamu. Based on the overview thus obtained, it appears that drug-adulteration presents important hazards responsible for potential adverse effects, due to overdosing. The potential hazards of exposure to APIs mainly relate to the presence of constituents that may cause liver damage, renal impairment, kidney failure, steroid dependence or genotoxicity and carcinogenicity. For these APIs, a risk characterisation was performed based on comparison of health-based guidance values (HBGVs) and exposure, while for the genotoxic carcinogens the margin of exposure (MOE) approach was used. Results of this risk characterisation should be used by risk managers to impose specification for constituents of health concern to protect consumers. It is concluded that to manage the risks identified and further improve the safety in use of jamu, a collaboration between farmers, manufacturer/producers, academia, government, health professionals, and consumers is indicated.

Evaluation of the nephrotoxicity and safety of low-dose aristolochic acid, extending to the use of Xixin (Asurum), by determination of methylglyoxal and d-lactate

ETHNOPHARMACOLOGICAL RELEVANCE

Most Aristolochiaceae plants are prohibited due to aristolochic acid nephropathy (AAN), except Xixin (Asarum spp.). Xixin contains trace amounts of aristolochic acid (AA) and is widely used in Traditional Chinese Medicine. Methylglyoxal and d-lactate are regarded as biomarkers for nephrotoxicity.

AIM OF THE STUDY

The use of Xixin (Asarum spp.) is essential and controversial. This study aimed to evaluate tubulointerstitial injury and interstitial renal fibrosis by determining urinary methylglyoxal and d-lactate after withdrawal of low-dose AA in a chronic mouse model.

MATERIALS AND METHODS

C3H/He mice in the AA group (n = 24/group) were given ad libitum access to distilled water containing 3 μg/mL AA (0.5 mg/kg/day) for 56 days and drinking water from days 57 to 84. The severity of tubulointerstitial injury and fibrosis were evaluated using the tubulointerstitial histological score (TIHS) and Masson's trichrome staining. Urinary and serum methylglyoxal were determined by high-performance liquid chromatography (HPLC); urinary d-lactate were determined by column-switching HPLC.

RESULTS

After AA withdrawal, serum methylglyoxal in the AA group increased from day 56 (429.4 ± 48.3 μg/L) to 84 (600.2 ± 99.9 μg/L), and peaked on day 70 (878.3 ± 171.8 μg/L; p < 0.05); TIHS and fibrosis exhibited similar patterns. Urinary methylglyoxal was high on day 56 (3.522 ± 1.061 μg), declined by day 70 (1.583 ± 0.437 μg) and increased by day 84 (2.390 ± 0.130 μg). Moreover, urinary d-lactate was elevated on day 56 (82.10 ± 18.80 μg) and higher from day 70 (201.10 ± 90.82 μg) to 84 (193.28 ± 61.32 μg).

CONCLUSIONS

Methylglyoxal is induced after AA-induced tubulointerstitial injury, so methylglyoxal excretion and metabolism may be a detoxification and repair strategy. A low cumulative AA dose is the key factor that limits tubulointerstitial injury and helps to repair. Thus, AA-containing herbs, especially Xixin, should be used at low doses for short durations (less than one month).

Defining in vivo dose-response curves for kidney DNA adduct formation of aristolochic acid I in rat, mouse and human by an in vitro and physiologically based kinetic modeling approach

Aristolochic acid I (AAI) is a well-known genotoxic kidney carcinogen. Metabolic conversion of AAI into the DNA-reactive aristolactam-nitrenium ion is involved in the mode of action of tumor formation. This study aims to predict in vivo AAI-DNA adduct formation in the kidney of rat, mouse and human by translating the in vitro concentration-response curves for AAI-DNA adduct formation to the in vivo situation using physiologically based kinetic (PBK) modeling-based reverse dosimetry. DNA adduct formation in kidney proximal tubular LLC-PK1 cells exposed to AAI was quantified by liquid chromatography-electrospray ionization-tandem mass spectrometry. Subsequently, the in vitro concentration-response curves were converted to predicted in vivo dose-response curves in rat, mouse and human kidney using PBK models. Results obtained revealed a dose-dependent increase in AAI-DNA adduct formation in the rat, mouse and human kidney and the predicted DNA adduct levels were generally within an order of magnitude compared with values reported in the literature. It is concluded that the combined in vitro PBK modeling approach provides a novel way to define in vivo dose-response curves for kidney DNA adduct formation in rat, mouse and human and contributes to the reduction, refinement and replacement of animal testing.

Toxicological Investigations of Aristolochia longa Root Extracts

Aristolochia longa L. (Aristolochiaceae) is an herbaceous plant recognized in alternative medicine for its many therapeutic virtues. The aim of this study was to determine the pharmacotoxicological effects of this plant in order to ensure safe clinical use. The oral toxicity of the aqueous extract of A. longa roots was performed in vivo on Wistar rats at doses of 0.8, 1.25, 2, 2.5, and 5 g/kg/day for 21 days. Clinical signs were observed throughout the experimental period, followed by measurement of body weight change, while selected biochemical parameters, as well as relative organ weights and the histology of liver, kidney, and intestinal tissues, were evaluated after 6, 11, and 16 days and then at the end of 21 days of daily administration. At repeated doses for 21 days, the extract contributed to significant weight gain, in both control and treated rats. The global analysis of hepatic and renal biomarkers showed a significant increase between control and different doses of the extract, from the first to the third week of treatment, indicating the likely toxic effect of the extract on liver and kidney function. Organ toxicity was confirmed by histopathological examination, which revealed greater renal and hepatic parenchymal changes in animals treated with a high dose beyond the 16th day. At the end of the treatment, relatively small size of intestinal villi was also observed. It was concluded that ALAE has a low toxicity potential in nonprolonged oral administrations. However, at high chronic oral doses, A. longa appears to have significant toxicity on the organs tested.

A Review on Recent Trends in Green Synthesis of Gold Nanoparticles for Tuberculosis

Tuberculosis (TB) is a contagious disease that has affected mankind. The anti-TB treatment has been used from ancient times to control symptoms of this disease but these medications produced some serious side effects. Herbal products have been successfully used for the treatment of TB. Gold is the most biocompatible metal among all available for biomedical purposes so Gold nanoparticles (GNPs) have sought attention as an attractive biosynthesized drug to be studied in recent years for bioscience research. GNPs are used as better catalysts and due to unique small size, physical resemblance to physiological molecules, biocompatibility and non-cytotoxicity extensively used for various applications including drug and gene delivery. Greenly synthesized GNPs have much more potential in different fields because phytoconstituents used in GNP synthesis itself act as reducing and capping agents and produced more stabilized GNPs. This review is devoted to a discussion on GNPs synthesis with herbs for TB. The main focus is on the role of the natural plant bio-molecules involved in the bioreduction of metal salts during the GNPs synthesis with phytoconstituents used as antitubercular agents.

In Vivo Metabolism of Aristolochic Acid I and II in Rats Is Influenced by Their Coexposure

The plant extract aristolochic acid (AA), containing aristolochic acid I (AAI) and II (AAII) as major components, causes aristolochic acid nephropathy and Balkan endemic nephropathy, unique renal diseases associated with upper urothelial cancer. Differences in the metabolic activation and detoxification of AAI and AAII and their effects on the metabolism of AAI/AAII mixture in the plant extract might be of great importance for an individual's susceptibility in the development of AA-mediated nephropathies and malignancies. Here, we investigated in vivo metabolism of AAI and AAII after ip administration to Wistar rats as individual compounds and as AAI/AAII mixture using high performance liquid chromatography/electrospray ionization mass spectrometry. Experimental findings were supported by theoretical calculations using density functional theory. We found that exposure to AAI/AAII mixture affected the generation of their oxidative and reductive metabolites formed during Phase I biotransformation and excreted in rat urine. Several Phase II metabolites of AAI and AAII found in the urine of exposed rats were also analyzed. Our results indicate that AAI is more efficiently metabolized in rats in vivo than AAII. Whereas AAI is predominantly oxidized during in vivo metabolism, its reduction is the minor metabolic pathway. In contrast, AAII is mainly metabolized by reduction. The oxidative reaction only occurs if aristolactam II, the major reductive metabolite of AAII, is enzymatically hydroxylated, forming aristolactam Ia. In AAI/AAII mixture, the metabolism of AAI and AAII is influenced by the presence of both AAs. For instance, the reductive metabolism of AAI is increased in the presence of AAII while the presence of AAI decreased the reductive metabolism of AAII. These results suggest that increased bioactivation of AAI in the presence of AAII also leads to increased AAI genotoxicity, which may critically impact AAI-mediated carcinogenesis. Future studies are needed to explain the underlying mechanism(s) for this phenomenon.

Identification of Aristolactam Derivatives That Act as Inhibitors of Human Immunodeficiency Virus Type 1 Infection and Replication by Targeting Tat-Mediated Viral Transcription

Despite the success of antiretroviral therapy (ART), efforts to develop new classes of antiviral agents have been hampered by the emergence of drug resistance. Dibenzo-indole-bearing aristolactams are compounds that have been isolated from various plants species and which show several clinically relevant effects, including anti-inflammatory, antiplatelet, and anti-mycobacterial actions. However, the effect of these compounds on human immunodeficiency virus type 1 (HIV-1) infection has not yet been studied. In this study, we discovered an aristolactam derivative bearing dibenzo[cd,f]indol-4(5H)-one that had a potent anti-HIV-1 effect. A structure-activity relationship (SAR) study using nine synthetic derivatives of aristolactam identified the differing effects of residue substitutions on the inhibition of HIV-1 infection and cell viability. Among the compounds tested, 1,2,8,9-tetramethoxy-5-(2-(piperidin-1-yl)ethyl)-dibenzo[cd,f]indol-4(5H)-one (Compound 2) exhibited the most potent activity by inhibiting HIV-1 infection with a half-maximal inhibitory concentration (IC₅₀) of 1.03 μmol/L and a half-maximal cytotoxic concentration (CC₅₀) of 16.91 μmol/L (selectivity index, 16.45). The inhibitory effect of the compounds on HIV-1 infection was linked to inhibition of the viral replication cycle. Mode-of-action studies showed that the aristolactam derivatives did not affect reverse transcription or integration; instead, they specifically inhibited Tat-mediated viral transcription. Taken together, these findings show that several aristolactam derivatives impaired HIV-1 infection by inhibiting the activity of Tat-mediated viral transcription, and suggest that these derivatives could be antiviral drug candidates.

Synthesis of 3-Alkylideneisoindolin-1-ones via Sonogashira Cyclocarbonylative Reactions of 2-Ethynylbenzamides

Cyclocarbonylative Sonogashira reactions of ortho-ethynylbenzamides have been investigated. The process is carried out under CO pressure, in the presence of a very small amount of PdCl₂(PPh₃)₂ (0.4 mol %) as a catalytic precursor and without the need for a Cu salt as the co-catalyst. 2-Ethynylbenzamide reacted successfully with iodoarenes bearing electron-withdrawing and electron-donating groups, giving rise to different classes of compounds depending on the solvent used. On the contrary, N-(4-chlorophenyl)-2-ethynylbenzamide afforded exclusively polyfunctionalized isoindolinones with high stereoselectivity toward (E) isomers.

Effect of prednisolone on glyoxalase 1 in an inbred mouse model of aristolochic acid nephropathy using a proteomics method with fluorogenic derivatization-liquid chromatography-tandem mass spectrometry

Prednisolone is involved in glucose homeostasis and has been used for treatment for aristolochic acid (AA) nephropathy (AAN), but its effect on glycolysis in kidney has not yet been clarified. This study aims to investigate the effect in terms of altered proteins after prednisolone treatment in a mice model of AAN using a proteomics technique. The six-week C3H/He female mice were administrated AA (0.5 mg/kg/day) for 56 days. AA+P group mice were then given prednisolone (2 mg/kg/day) via oral gavage for the next 14 days, and AA group mice were fed water instead. The tubulointerstitial damage was improved after prednisolone treatment comparing to that of AA group. Kidney homogenates were harvested to perform the proteomics analysis with fluorogenic derivatization-liquid chromatography-tandem mass spectrometry method (FD-LC-MS/MS). On the other hand, urinary methylglyoxal and D-lactate levels were determined by high performance liquid chromatography with fluorescence detection. There were 47 altered peaks and 39 corresponding proteins on day 14 among the groups, and the glycolysis-related proteins, especially glyoxalase 1 (GLO1), fructose-bisphosphate aldolase B (aldolase B), and triosephosphate isomerase (TPI), decreased in the AA+P group. Meanwhile, prednisolone decreased the urinary amount of methylglyoxal (AA+P: 2.004 ± 0.301 μg vs. AA: 2.741 ± 0.630 μg, p < 0.05), which was accompanied with decrease in urinary amount of D-lactate (AA+P: 54.07 ± 5.45 μmol vs. AA: 86.09 ± 8.44 μmol, p < 0.05). Prednisolone thus alleviated inflammation and interstitial renal fibrosis. The renal protective mechanism might be associated with down-regulation of GLO1 via reducing the contents of methylglyoxal derived from glycolysis. With the aid of proteomics analysis and the determination of methylglyoxal and its metabolite-D-lactate, we have demonstrated for the first time the biochemical efficacy of prednisolone, and urinary methylglyoxal and its metabolite-D-lactate might be potential biomarkers for AAN.

Biotransformation and Toxicities of Aristolochic Acids

Environmental and iatrogenic exposures contribute significantly to human diseases, including cancer. The list of known human carcinogens has recently been extended by the addition of aristolochic acids (AAs). AAs occur primarily in Aristolochia herbs, which are used extensively in folk medicines, including Traditional Chinese Medicine. Ingestion of AAs results in chronic renal disease and cancer. Despite importation bans imposed by certain countries, herbal remedies containing AAs are readily available for purchase through the internet. With recent advancements in mass spectrometry, next generation sequencing, and the development of integrated organs-on-chips, our knowledge of cancers associated with AA exposure, and of the mechanisms involved in AA toxicities, has significantly improved. DNA adduction plays a central role in AA-induced cancers; however, significant gaps remain in our knowledge as to how cellular enzymes promote activation of AAs and how the reactive species selectively bind to DNA and kidney proteins. In this review, I describe pathways for AAs biotransformation, adduction, and mutagenesis, emphasizing novel methods and ideas contributing to our present understanding of AA toxicities in humans.

QuEChERS pretreatment combined with high-performance liquid chromatography-tandem mass spectrometry for determination of aristolochic acids I and II in Chinese herbal patent medicines

Aristolochic acid I and II (AA I and II), a kind of nephrotoxic and carcinogenic compound, are widely added in Chinese herbal patent medicines though they have been banned due to their toxicity. However, the traditional sample pre-treatment combined with the LC-MS analysis system is not effective to determine AAs in such complicated patent medicines. The QuEChERS pretreatment method possesses some merits such as being quick and effective. In this work, the modified QuEChERS method was first used to determine AA I and II in Chinese herbal patent medicines combined with the HPLC-MS/MS analysis system. Extraction and removal of target analytes from powder, tablet, and capsule samples were conducted using the modified QuEChERS pretreatment. The liquid extracts of Chinese herbal patent medicines could be analyzed directly. The method optimization results show that average recoveries ranged from 96.6% to 110.3% with relative standard deviations ranging from 4.2% to 13.0%. The quantization limits of the three selected matrices are estimated as follows (AA I/II): 2.8/6.5 ng mL^−l in liquid herbal extract, 6.5/12.5 ng g⁻¹ in tablets, and 22.1/42.1 ng g⁻¹ in capsules. This method was conducted to investigate the presence of AAs, which are a type of nephrotoxic and carcinogenic carboxylic acid, in 30 herbal products sold through the Internet in China. AA I and II were detected in 53% and 20%, respectively, of tested samples.

Aristolochic acid I and II (AA I and II), a kind of nephrotoxic and carcinogenic compound, are widely added in Chinese herbal patent medicines though they have been banned due to their toxicity.

Bioactivation mechanisms of N-hydroxyaristolactams: Nitroreduction metabolites of aristolochic acids

Aristolochic acids (AAs) are human nephrotoxins and carcinogens found in concoctions of Aristolochia plants used in traditional medicinal practices worldwide. Genotoxicity of AAs is associated with the formation of active species catalyzed by metabolic enzymes, the full repertoire of which is unknown. Recently, we provided evidence that sulfonation is important for bioactivation of AAs. Here, we employ Salmonella typhimurium umu tester strains expressing human N-acetyltransferases (NATs) and sulfotransferases (SULTs), to study the role of conjugation reactions in the genotoxicities of N-hydroxyaristolactams (AL-I-NOH and AL-II-NOH), metabolites of AA-I and AA-II. Both N-hydroxyaristolactams show stronger genotoxic effects in umu strains expressing human NAT1 and NAT2, than in the parent strain. Additionally, AL-I-NOH displays increased genotoxicity in strains expressing human SULT1A1 and SULT1A2, whereas AL-II-NOH shows enhanced genotoxicity in SULT1A1/2 and SULT1A3 strains. 2,6-Dichloro-4-nitrophenol, SULTs inhibitor, reduced umuC gene expression induced by N-hydroxyaristolactams in SULT1A2 strain. N-hydroxyaristolactams are also mutagenic in parent strains, suggesting that an additional mechanism(s) may contribute to their genotoxicities. Accordingly, using putative SULT substrates and inhibitors, we found that cytosols obtained from human kidney HK-2 cells activate N-hydroxyaristolactams in aristolactam-DNA adducts with the limited involvement of SULTs. Removal of low-molecular-weight reactants in the 3.5-10 kDa range inhibits the formation of aristolactam-DNA by 500-fold, which could not be prevented by the addition of cofactors for SULTs and NATs. In conclusion, our results demonstrate that the genotoxicities of N-hydroxyaristolactams depend on the cell type and involve not only sulfonation but also N,O-acetyltransfer and an additional yet unknown mechanism(s). Environ. Mol. Mutagen. 2019. © 2019 Wiley Periodicals, Inc.

Phytochemical Analysis and Toxicity Study of Aristolochia paucinervis Rhizomes Decoction Used in Moroccan Alternative Medicine: Histopathological and Biochemical Profiles

Ethnopharmacological Relevance

Aristolochia paucinervis (A. paucinervis) (Aristolochiaceae) is a plant frequently used in Moroccan alternative medicine. The aim of the current study is to investigate the phytochemical composition of rhizomes decoction of A. paucinervis (RDA) and to evaluate its acute and subacute toxicity following the OECD guidelines.

Materials and Methods

The qualitative phytochemical analysis of A. paucinervis was performed using standard qualitative phytochemical procedures. The acute toxicity of rhizomes decoction of the studied plant was evaluated in mice at single doses of 1, 2, and 4 g/kg of body weight for 14 days. In subacute toxicity study, the decoction was orally administered to mice at three different doses (0.5, 1, and 1.5 g/kg/day) for 28 days. Histopathological and biochemical parameters were investigated.

Results

The preliminary phytochemical screening showed the presence of flavonoids, saponins, alkaloids, and polyphenols and the absence of anthraquinones, sterols, and terpenes. There was no mortality and no significant changes occurred in animals treated with 1 and 2 g/kg in the acute toxicity model. The signs of toxicity and morbidity were remarkable with the highest tested dose (4g/kg). LD₅₀ (dose required to kill 50% of the test population) was determined as 4 g/kg. Repeated oral administration of 1 and 1.5 g/kg/day of RDA for 28 days induced significant disturbance of serum parameters (AST, ALT, LDH, urea, creatinine). Kidney and liver extracted from mice fed with 1 and 1.5 g/kg/day showed significant histopathological injuries as tubular necrosis, inflammatory infiltrate, tubular degeneration, necrosis, and hepatic cholestasis. Meanwhile, neither histopathological nor biochemical alterations were observed in mice treated with 0.5 g/kg/day of body weight in comparison to the control group.

Conclusion

RDA showed toxicity in mice at a dose of 1 g/kg/day under subacute toxicity conditions. RDA is safe at a single dose inferior to 4 g/kg of body weight. The plant extract prepared by decoction showed more poisonous effect than the extract prepared by maceration at room temperature.

Stereoselective Total Synthesis of (+)-Aristolactam GI

Aristolactams are an important subgroup of aporphinoids, which all share a common phenanthrene chromophore motif that is thought to be responsible for the range of interesting physicochemical and biological properties exhibited by these compounds. Among all of the aristolactams discovered, (+)-aristolactam GI displays a unique structural feature of having the aristolactam scaffold linked via a benzodioxane ring to a phenyl propanoid unit, resulting in the compound being an aporphinoid-lignan hybrid. The synthesis of (+)-aristolactam GI was achieved first by synthesis of an orthogonally protected aristolactam, which was prepared using a Suzuki/aldol cascade to convert a differentially protected isoindolin-1-one to the required phenanthrene. The required enantiopure phenyl propanoid unit was prepared from readily available ( R)-methyl lactate. A selective Mitsunobu reaction was used to combine these two key fragments, prior to the formation of the linking benzodioxane in the final step. The absolute stereochemistry of the natural product was confirmed to be 7' S, 8' S.

Worldwide research trends on aristolochic acids (1957-2017): Suggestions for researchers

Aristolochic acids and their derivatives are components of many traditional medicines that have been used for thousands of years, particularly in Asian countries. To study the trends of research into aristolochic acids and provide suggestions for future study, we performed the following work. In this paper, we performed a bibliometric analysis using CiteSpace and HistCite software. We reviewed the three phases of the development of aristolochic acids by using bibliometrics. In addition, we performed a longitudinal review of published review articles over 60 years: 1,217 articles and 189 review articles on the history of aristolochic acid research published between 1957 and 2017 were analyzed. The performances of relevant countries, institutions, and authors are presented; the evolutionary trends of different categories are revealed; the history of research into aristolochic acids is divided into three phases, each of which has unique characteristics; and a roadmap of the historical overview of aristolochic acid research is finally established. Finally, five pertinent suggestions for future research into aristolochic acid are offered: (1) The study of the antitumor efficacy of aristolochic acids is of value; (2) The immune activity of aristolochic acids should be explored further; (3) Researchers should perform a thorough overview of the discovery of naturally occurring aristolochic acids; (4) More efforts should be directed toward exploring the correlation between aristolochic acid mutational signature and various cancers; (5) Further efforts should be devoted to the research and review work related to analytical chemistry. Our study is expected to benefit researchers in shaping future research directions.

Phytochemical Screening and Toxicological Study of Aristolochia baetica Linn Roots: Histopathological and Biochemical Evidence

Aristolochia baetica (A. baetica) is a wild species of Aristolochiaceae family; its roots are used by Moroccan people against cancer for many years ago. The objective of the study was to investigate the phytochemical screening, acute and subacute toxicity of A. baetica roots growing in the north of Morocco. Qualitative and quantitative analyses of A. baetica roots were performed using standard methods; the acute toxicity of the root extract of the studied plant was assessed in mice by gavage of single doses of 1, 2, and 4 g/kg body weight for 14 days; by the time the subacute toxicity was done using repeated doses 1, 1.5, and 2 g/kg/day for 28 days. Histological changes and biochemical parameters as markers of kidney and liver function were evaluated. The results of phytochemical screening showed the presence of polyphenols, tannins, alkaloids, flavonoids, saponins, and the absence of anthraquinones, sterols, and terpenes. The results of acute toxicity showed the absence of mortality and signs of toxicity in groups treated with 1 and 2 g/kg; however, the clinical signs of toxicity were important and the rate of mortality was estimated at 16 % in the group treated with 4 g/kg. The results of subacute toxicity showed several changes of serum parameters registered in groups treated with 1.5 and 2 g/kg/day, respectively. The results showed also the absence of histological injuries in groups treated with 1 and 1.5 g/kg/day; meanwhile, the histological alterations were remarkable in treated group with the highest dose administered of 2 g/kg/day. The outcome of this work showed that the roots' extract of the studied plant was toxic in mice with repeated doses, but no toxic effect was observed with a single dose under 4g/kg.