Type Alkaloids Research Articles

Alkaloids as Natural NRF2 Inhibitors: Chemoprevention and Cytotoxic Action in Cancer.

Being a controller of cytoprotective actions, inflammation, and mitochondrial function through participating in the regulation of multiple genes in response to stress-inducing endogenous or exogenous stressors, the transcription factor Nuclear Factor Erythroid 2-Related Factor 2 (NRF2) is considered the main cellular defense mechanism to maintain redox balance at cellular and tissue level. While a transient activation of NRF2 protects normal cells under oxidative stress, the hyperactivation of NRF2 in cancer cells may help them to survive and to adapt under oxidative stress. This can be detrimental and related to cancer progression and chemotherapy resistance. Therefore, inhibition of NRF2 activity may be an effective approach for sensitizing cancer cells to anticancer therapy. In this review, we examine alkaloids as NRF2 inhibitors from natural origin, their effects on cancer therapy, and/or as sensitizers of cancer cells to anticancer chemotherapeutics, and their potential clinical applications. Alkaloids, as inhibitor of the NRF2/KEAP1 signaling pathway, can have direct (berberine, evodiamine, and diterpenic aconitine types of alkaloids) or indirect (trigonelline) therapeutic/preventive effects. The network linking alkaloid action with oxidative stress and NRF2 modulation may result in an increased NRF2 synthesis, nuclear translocation, as well in a downstream impact on the synthesis of endogenous antioxidants, effects strongly presumed to be the mechanism of action of alkaloids in inducing cancer cell death or promoting sensitivity of cancer cells to chemotherapeutic agents. In this regard, the identification of additional alkaloids targeting the NRF2 pathway is desirable and the information arising from clinical trials will reveal the potential of these compounds as a promising target for anticancer therapy.

A review on efforts for improvement in medicinally important chemical constituents inAconitum through biotechnological interventions.

The genus Aconitum belongs to the family Ranunculaceae, is endowed with more than 350 species on the earth. Medicinally important aconitine type of diterpenoid alkaloids are the characteristic compounds in most of the Aconitum species. The present review endeavored the major research carried out in the field of genetic resource characterization, pharmacological properties, phytochemistry, major factors influencing quantity, biosynthetic pathways and processing methods for recovery of active ingredients, variety improvement, propagation methods, and important metabolite production through cell/organ culture of various Aconitum species. More than 450 derivatives of aconitine-type C19 and C20-diterpenoid alkaloids along with a few other non-alkaloidal compounds, such as phenylpropanoids, flavonoids, terpenoids, and fatty acids, have been identified in the genus. A few Aconitum species and theircommon diterpenoid alkaloid compounds are also well characterized for analgesic, inflammatory and cytotoxic properties. However, the different isolated compound needs to be validated for supporting other traditional therapeutical uses of the plant species. Aconitine alkaloids shared common biosynthesis pathway, but their diversification mechanism remains unexplored in the genus. Furthermore, the process needs to be developed on secondary metabolite recovery, mass-scale propagation methods, and agro-technologies for maintaining the quality of products. Many species are losing their existence in nature due to over-exploitation or anthropogenic factors; thus, temporal monitoring of the population status in its habitat, and suitable management programs for ascertaining conservation needs to be developed.

Total Synthesis of Vinorine

The asymmetric total synthesis of vinorine, a polycyclic and cage-like alkaloid, has been realized in a flexible approach. Key features of the current synthesis include an aza-Achmatowicz rearrangement/Mannich-type cyclization to install the highly functional 9-azabicyclo-[3.3.1]nonane scaffold, a high yield Fischer indole annulation to synthesize the common intermediate for sarpagine-ajamaline type alkaloids, and an Ireland-Claisen rearrangement to construct the C15-C20 bond.

GC-MS of some Amaryllidaceae alkaloids of homolycorine type.

Gas chromatography-mass spectrometry (GC-MS) is the most frequently applied technique for analysis of Amaryllidaceae alkaloids in plant extracts. These compounds, known for their potent bioactivities, are a distinctive chemotaxonomic feature of the Amaryllidoideae subfamily (Amaryllidaceae). The Amaryllidaceae alkaloids of homolycorine type with a C3-C4 double bond generally show molecular and diagnostic ions at the high mass region with low intensity in EIMS mode leading to problematic identification in complex plant extracts. Eleven standard homolycorine-type alkaloids (isolated and identified by 1D and 2D nuclear magnetic resonance) were subjected to separation with gas chromatography and studied with electron impact mass spectrometry including single quadropole (GC-EIMS), tandem (GC-EIMS/MS), and high resolution (GC-HR-EIMS) detectors, as well as with chemical ionisation mass spectrometry (GC-CIMS). Alkaloid fractions from two Hippeastrum species and Clivia miniata were subjected to GC-EIMS and GC-CIMS for alkaloid identification. GC-EIMS in combination with GC-CIMS provided significant structural information for homolycorine-type alkaloids with C3-C4 double bond facilitating their unambiguous identification. Based on the obtained typical fragmentation, other eleven homolycorine-type compounds were identified in extracts from two Hippeastrum species by parallel GC-EIMS, GC-CIMS and LC-ESI/ToF/MS and in extracts from Clivia miniata by GC-EIMS. GC-MS can be successfully applied for identification of new and known homolycorine-type alkaloids, as well as for chemotaxonomical and chemoecological studies, among others within the Amaryllidoideae subfamily.

Chemical constituents, pharmacological effects, toxicology, processing and compatibility of Fuzi (lateral root of Aconitum carmichaelii Debx): A review.

The lateral root of Aconitum carmichaelii Debx is known as Fuzi in Chinese. It is traditionally valued and used for dispelling cold, relieving pain effects, restoring 'Yang,' and treating shock despite its high toxicity. This review aims to provide comprehensive information on the chemical composition, pharmacological research, preparation, and compatibility of Fuzi to help reduce its toxicity and increase its efficiency, based on the scientific literature. In addition, this review will establish a new foundation for further studies on Fuzi. A systematic review of the literature on Fuzi was performed using several resources, namely classic books on Chinese herbal medicine and various scientific databases, such as PubMed, the Web of Science, and the China Knowledge Resource Integrated databases. Fuzi extracts contain diester-type alkaloids, monoester-type alkaloids, other types of alkaloids, and non-alkaloids types, and have various pharmacological activities, such as strong heart effect, effect on blood vessels, and antidepressant, anti-diabetes, anti-inflammatory, pain-relieving, antitumor, immunomodulatory, and other therapeutic effects. However, these extracts can also lead to various toxicities such as cardiotoxicity, neurotoxicity, reproductive toxicity, hepatotoxicity, and embryonic toxicity. In vivo and in vitro experiments have demonstrated that different processing methods and suitable compatibility with other herbs can effectively reduce the toxicities and increase the efficiency of Fuzi. The therapeutic potential of Fuzi has been demonstrated in conditions, such as heart failure, various pains, inflammation, and tumors, which is attributed to the diester-type alkaloids, monoester-type alkaloids, other types of alkaloids, and non-alkaloid types. In contrast, they are also toxic components. Proper processing and suitable compatibility can effectively reduce toxicity and increase the efficiency of Fuzi. Thus more pharmacological and toxicological mechanisms on main active compounds are necessary to be explored.

Formulation and evaluation of orally disintegrating film (ODF) containing piperine-succinic acid cocrystal

Piperine is a type of alkaloid found in plants of the Piperaceae family, including Piper nigrum and Piper longum , which has numerous pharmacological properties and is being developed as a nutraceutical. However, its poor solubility makes delivering in effective doses for therapeutic purposes challenging. To overcome this limitation, the cocrystals of piperine and succinic acid was prepared, which are more soluble, and then formulated into orally disintegrating films (ODFs) for better delivery. The cocrystals were formed using the slurry method, while the ODFs were made using the solvent-casting method with different concentrations of hydroxypropyl methylcellulose (HPMC) and polyethylene glycol (PEG) 400. The resulting films were evaluated for various parameters, such as their organoleptic characteristics, weight and thickness uniformity, pH, moisture content, swelling properties, and disintegration time. The results showed that the ODF with 6% HPMC as a film-forming polymer and 0.6% PEG 400 as a plasticizer loaded with 10 mg of piperine in the form of piperine-succinic acid cocrystal was the best formula. This ODF formulation disintegrated in less than one minute and was found to be a good film with uniform content.

Study of the effect of Cladophora crispate and Annona squamosa L.,alkaloids without or with albendazole on weights of mice infected with hydatid cysts

The current study is aimed to test the incidence of infection at injection mice with protoscolices and evaluate the effectiveness of the effective compound derived from the algae Cladophora crispate and plant Annona squamosa L and compare it with albendazole at the infected with hydatid cysts. The results of the current study show that there is a decrease in the average weight of infected mice and treatment with active substances alkaloids without or with albendazole compared to the positive control group as the effect of the mixed drug (algae , plant and albendazole) .Concentrate (0.6 mg / ml ) had given a therapeutic efficacy amount (82.35% ) and gave a percentage of cystic fibers ( 80.0 %) compared with the rest of the concentration the active ingredient drug. This study found that the combination of both types of alkaloids algae Cladophora crispate and plant Annona squamosa L wih albendazole had the greatest effect in reducing weights of infected mice with hydatid cysts.

Pyrrolizidine alkaloids and health risk of three Boraginaceae used in TCM.

Objective: The aim of this study was to systematically explore the pyrrolizidine alkaloids (PAs) type, content and risk assessment in the three Boraginaceae used in TCM, involving Arnebia euchroma (AE), A. guttata (AG), and Lithospermum erythrorhizon (LE). Method: A UHPLC-MS/MS method was established to simultaneously determine eight pyrrolizidine alkaloids (PAs), namely intermedine, lycopsamine, intermedine N-oxide, lycopsamine N-oxide, 7-acetyllycopsamine, 7-acetyllycopsamine N-oxide, echimidine N-oxide, and echimidine in the three herbs. Based on these results, the risk assessment was explored using the routine margin of exposure (MOE) combined with relative potency (REP) for oral and external usage, respectively. Results and Conclusion: Imermedine and imermedine N-oxide were common components in the eight tested PAs. 7-acetyllycopsamine and its N-oxide were not detected in AE; echimidine and its N-oxide were not detected in AG; lycopsamine and its N-oxide, 7-acetyllycopsamine and its N-oxide were not detected in LE. The total contents of 8 PAs in 11 batches of AG was341.56-519.51 μg/g; the content in 15 batches of LE was 71.16-515.73 μg/g, and the content in 11 batches of AE was 23.35-207.13 μg/g. Based on these results, the risk assessment was explored using MOE combined with REP for oral and external usage, respectively. The findings of the risk assessment method of PAs based on MOE combined with the REP factor were consistent with the clinical toxicity results. As an oral herb, AE had low risk or no risk due to its low PA contents, and individual batches of LE were medium risk, while attention should be paid to their clinical use.AG was also low risk. The external use of the three Boraginaceae used in TCM was not associated with any risk. This study systematically explored the PA type and content of the three Boraginaceae used in TCM. Additionally, the refined risk assessment of PAs based on REP provided a more scientific basis for quality evaluation and rational use of the medicinal Boraginaceae used in TCM to improve public health.

Isocorydine Ameliorates IL-6 Expression in Bone Marrow-Derived Macrophages and Acute Lung Injury Induced by Lipopolysaccharide.

Isocorydine (ICD) is a type of isoquinoline alkaloid originating from Corydalis edulis, which has been used to relieve spasm, dilate blood vessels, and treat malaria as well as hypoxia in clinic. However, its effect on inflammation and underlying mechanisms remains unclear. The aim of our study was to determine the potential effects and mechanisms of ICD on pro-inflammatory interleukin-6 (IL-6) expression in bone marrow-derived macrophages (BMDMs) and acute lung injury mouse model. A mouse model of acute lung injury was established by intraperitoneal injection of LPS and treated with different doses of ICD. The body weight and food intake of mice were monitored to determine the toxicity of ICD. The tissue samples of lung, spleen and blood were taken to assess the pathological symptoms of acute lung injury and the expression levels of IL-6. Further, BMDMs isolated from C57BL/6 mice were cultured in vitro and treated with granulocyte-macrophage colony-stimulating factor (GM-CSF), LPS and different doses of ICD. CCK-8 assay and flow cytometry were performed to assess the viability of BMDMs. The expression of IL-6 was detected by RT-PCR and ELISA. RNA-seq was carried out to detect the differential expression genes of ICD-treated BMDMs. Western blotting was used to detect the change in MAPK and NF-κB signaling pathways. Our findings show that ICD ameliorates IL-6 expression and attenuates phosphorylation of p65 and JNK in BMDMs, and can protect mice from acute lung injury.

Rapid identification of chemical components in vitro and in vivo of Menispermi Rhizoma by integrating UPLC-Q-TOF-MS with data post-processing strategy.

Menispermi Rhizoma (MR), the dried rhizome of Menispermum dauricum DC. (Menispermaceae), has been used to treat sore throat, enteritis, dysentery, and rheumatic arthralgia. Despite extensive research on its pharmacological effects, the chemical components in vitro and in vivo have not been thoroughly studied. To establish an efficient method for rapid classification and identification of alkaloids in MR and its preparations, as well as metabolites in vivo after oral administration of MR. Rapid identification of alkaloids and absorbed components of MR was performed using ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) coupled with UNIFI software. Moreover, the characteristic fragmentations and neutral losses of different types of alkaloids in MR were summarised to realise the rapid classification of alkaloids. A total of 55 components were unambiguously or tentatively identified in MR. Among them, 37 and 31 components were found in MR capsules and tablets, respectively. Meanwhile, 109 compounds were tentatively identified in rat plasma, urine and faeces, including 55 prototypes and 54 metabolites. Hydrogenation, hydroxylation, methylation, glucuronic acid and sulphate conjugations were the dominating metabolic fates of alkaloids. The data post-processing strategy established could greatly enhance the structural identification efficiency. The results obtained might lay the foundation for further interpretation of clinical effects, mechanism of action and quality control of MR.

Structurally diverse monoterpene indole alkaloids with vasorelaxant activities from the branches of Alstonia scholaris

Seven undescribed monoterpene indole alkaloids alstoscholarinines A‒G, along with nineteen known alkaloids, were isolated from the branches of Alstonia scholaris (L.) R. Br. The isolated alkaloids were classified into ten framework types. The structures of the undescribed alkaloids were elucidated by extensive spectroscopic analysis, ECD calculation, and single-crystal X-ray diffraction analysis. Alstoscholarinine A is an unreported and unusual monoterpene indole alkaloid incorporating three nitrogen atoms, characterized by a compact 6/5/6/6/6/5 hexacyclic system bearing a piperidine ring and a unique oxazolidine ring. Alstoscholarinine B represents the first naturally C-17 nor-isositsirikine-type alkaloid. Plausible biosynthetic pathways of alstoscholarinines A and B were proposed. All isolates were evaluated for their vasorelaxant activities against phenylephrine-induced contraction of rat mesenteric arteries. Among them, seven alkaloids showed significant vasorelaxant activities with EC50 values less than 10 μM. Importantly, the akuammicine-type alkaloids in this study showed much better vasorelaxant activities than other framework type alkaloids, indicating that this type of alkaloid may be a valuable source for the discovery of vasodilators. A preliminary structure-activity relationship for vasorelaxant activities of the isolated akuammicine-type alkaloids is also discussed.

Alkaloids and Iridoids From the Aerial Parts of Rauvolfia cambodiana Pierre ex Pit. and Their Acetylcholinesterase Inhibitory Activity

Objective: Rauvolfia cambodiana has been used as a Vietnamese folk medicine to treat high blood pressure and for sedation and memory loss diseases. However, to date, there have been few studies on the chemical constituents and biological activity of this medicinal plant. This study aimed to find the chemical constituents of R cambodiana and evaluate their enhancement memory properties. Methods: The aerial parts of R cambodiana were powdered and ultrasonically extracted with methanol. The methanol extract was suspended in water and successively partitioned with dichloromethane and ethyl acetate to give dichloromethane, ethyl acetate, and water-soluble extracts. Each extract was fractionated and purified by column and HPLC chromatographic methods. The chemical structures of the isolated compounds were elucidated by analysis of HRESIMS, 1D and 2D NMR spectra, and experimental and TD-DFT calculated ECD spectra. The enhancement memory property of the compounds was evaluated by their in vitro acetylcholinesterase inhibitory activity. Results: Five alkaloids (1-5) and 2 iridoids (6 and 7), including one new one named rauvolcambonine (1), and 6 known compounds, perakine (2), ajmaline (3), 10-hydroxy-16- epi-affinine (4), sitsirikine (5), loganic acid (6), and secoxyloganin (7) were isolated and identified from the aerial parts of R cambodiana. Compounds 4 and 5 significantly showed acetylcholinesterase inhibitory effects in vitro with IC50 values of 30.1 ± 1.4 µM and 65.5 ± 3.3 µM, respectively. The other compounds inhibited acetylcholinesterase with IC50 values ranging from 111.0 ± 6.0 µM to 197.6 ± 19.8 µM. Conclusion: One new (1) and 3 other compounds (2, 4-7) were recorded from R cambodiana for the first time. The NMR spectroscopic data of compound 4 are reported herein for the first time. Our study preliminarily revealed that the vobasenal framework type alkaloids could be active ingredients of Rauvolfia species and responsibility for the enhancement memory property of these plants.

Isolation and Characterization of Compounds from Ochreinauclea maingayi (Hook. f.) Ridsd. (Rubiaceae) with the Aid of LCMS/MS Molecular Networking

Phytochemical investigation of the dichloromethane crude extract from the bark of Ochreinauclea maingayi with the aid of LCMS/MS-based molecular networking guided the isolation and accelerated the elucidation of known and new indole alkaloids. The molecular networking analysis produces two main clusters, along with 41 non-prioritized clusters and self-loop nodes. Each cluster has several nodes which depict the fractions contained within those nodes. An implementation of a fraction mapping for each node represents the molecular weight and key fragment data of each compound. From the analysis of each cluster and node, we can deduce the indole alkaloids are the scaffold of interest. Indole scaffold can be found between F5 and F10 that contain several types of indole alkaloids. In total, we have successfully purified nine indole alkaloids, including 9H-β-carboline-4-carboxylate 2, norharmane 3, harmane 4, naucledine 10, neonaucline 15, 1,2,3,4-tetranorharmane-1-one 16, naulafine 19, cadambine 9, and a new monoterpene indole alkaloid dihyrodeglycocadambine 7 from F5 to F10 using a chromatographic technique. Their structures were confirmed by 1D-NMR, 2D-NMR, UV, IR, LCMS, and MS2LDA. Several clusters and nodes contain ions that could not be annotated, suggesting that they may possess novel compounds that are yet to be discovered.

Review on medicinal and traditional importance of horse gram

Horse grame has a long history of usage as an antihypertensive and treatment for diseases and infections. Along with lipids and other types of proteins, many steroidal, alkaloid, and glycoside chemicals were present in horse gram as significant bioactive components. Rich source of milk protein, vitamins A and C, and other nutrients. It belongs to the Lamiaceae family and has 15 different genetic species that are primarily grown in Asia and Africa. Horse gram plant pieces can be eaten by both people and animals. Nevertheless, as dal, in making so-called rasam, and as a concentrated feed for animals. It can be utilised as green manure as well. It offered a variety of possible effects, including anti-inflammatory, hepatoprotective, anti-cancer, anti-fertility, anti-cancer, antibacterial, and antioxidant etc. These plants have a variety of medical qualities that can be found across the entire plant. This review's goal is to analyse and draw conclusions on the body of knowledge around the phytochemical make-up, therapeutic applications, and pharmacological effects of horse gramme and its constituent parts.

Structurally diverse alkaloids with nine frameworks from Zephyranthes candida and their acetylcholinesterase inhibitory and anti-inflammatory activities

Twenty-six structurally diverse Amaryllidaceae alkaloids, including ten undescribed compounds named zephyranines A–I and 6-O-ethylnerinine, two undescribed natural products zephyranthine-6-one and 3-O-deacetyl-sternbergine, were isolated from whole plants of Zephyranthes candida. Their structures were determined by HRESIMS, 1D and 2D NMR, CD data analysis, NMR and ECD calculations, and single-crystal X-ray diffraction analysis. All structures were classified into nine framework types: 10b,11-seco-crinine, graciline, crinine, homolycorine, trisphaeridine, lycorine, galasine, tazettine, and belladine. Zephyranine A represents the first naturally occurring 10b,11-seco-crinine type alkaloid, and zephyranine B is the sixth graciline type alkaloid. 6-O-ethylnerinine is an artifact from the extraction and isolation. All isolates were evaluated for their acetylcholinesterase (AChE) inhibitory and anti-inflammatory activities. Zephyranines A, G, and H exhibited moderate AChE inhibitory activities, with IC50 values of 8.2, 39.0, and 10.8 μM, respectively. Zephyranine B, haemanthamine, haemanthidine, 11-hydroxyvittatine, and 8-demethoxy-10-O-methylhostasine exhibited potent anti-inflammatory activity on the LPS-induced NO production in RAW264.7 mouse macrophages with IC50 values of 21.3, 4.6, 12.2, 5.6, and 17.4 μM, respectively. Structure-activity-relationship analysis and docking studies indicated that interactions with the key Trp286 and Tyr337 residues are required for potent AChE inhibitors.

Mitigative effect of caffeine against diclofenac-induced hepato-renal damage and chromosomal aberrations in male albino rats.

Among the most commonly consumed non-steroidal anti-inflammatory drugs (NSAID) is Diclofenac (Dic), especially in low-income countries due to its high efficiency and affordable price. However, the continuous administration of Diclofenac may induce toxic effects on various body organs including the liver and kidney. Caffeine (Caf) (1,3,7-trimethylxanthine) is a pharmacologically active alkaloid type with antioxidant and anti-inflammatory actions. The current study aims to evaluate the ameliorative effect of Caffeine against Dic-induced hepato-renal toxicity and damage. Twenty-four male albino rats type were assigned randomly into four groups (n = 6): (Group 1): Control group, (Group 2): Six male rats were exposed to Dic 10mg/kg intraperitoneally (I.P) for 28 days, (Group 3): Six male rats were exposed to Caf (15mg/kg orally) for 28 days; (Groups 4): Six male rats were exposed to Dic (10mg/kg, i.p) + Caf (15mg/kg, orally) for 28 days. Histopathological study and various biological parameters were estimated among the four groups including hemoglobin (Hb%) red blood cells (RBCs), Hematocrit (HT%), total leucocyte count (WBCs), lipid peroxidation (LPO), glutathione peroxidase (GPx), alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, creatinine, tumor necrosis factor-α (TNF-α), and nitric oxide (NO). The administration of Diclofenac resulted in significant deteriorations in the histopathological findings and estimated biological parameters. Whereas, daily Caffeine administration ameliorated Diclofenac-induced toxicity in the kidney and liver by three mechanisms including antioxidant, anti-inflammatory, and DNA damage inhibition. The current study demonstrated the promising ameliorative and protective effects of Caffeine against Diclofenac-induced hepatic and renal injury.

Amaryllidaceae alkaloids from Lycoris suppress amyloid β-induced neurodegeneration in transgenic Caenorhabditis elegans CL2355

Alzheimer’s disease (AD) accounts for 60–80 % of dementia cases worldwide and has no effective treatment currently, presenting a pressing need to search for new anti-AD agents. One of the AD therapeutic options is to improve the cognitive impairment by restoring the characteristic cholinergic deficiency with acetylcholinesterase (AChE) inhibitors. It has been previously shown that the natural Amaryllidaceae alkaloids galanthamine and haemanthidine from Lycoris radiata inhibit the ace-2 gene expression in transgenic CL4176 C. elegans . The aim of this project was to screen and characterize the Amaryllidaceae alkaloids extracted from twelve Lycoris species. Different type of alkaloids were tentatively identified by UPLC-QTOF-MS method. Three alkaloids lycorine, lycoramine and galanthamine were quantified in these species. These Lycoris alkaloids were shown to reduce the toxicity and the neurodegeneration induced by the neuronal expression of amyloid β in transgenic CL2355 C. elegans by a serotonin assay and to collectively inhibit the ace-2 gene expression by both qRT-PCR and BLItz™ analyses. The active species includes L. chinensis , L. caldwellii , L. squamigera and L. incarnate . The alkaloid metabolite profiling results indicate that these active species are rich in different alkaloids, which are potential markers for anti-Alzheimer disease. • Amaryllidaceae alkaloids were characterizing from twelve Lycoris species. • Forty-two alkaloids belonging to ten chemotypes were identified by UPLC-QTOF-MS. • Some species showed activities in anti- ace2 gene expression and anti-amyloid β. • Lycoris alkaloids markers are promising in anti-Alzheimer disease.

Profiles of Metabolic Genes in Uncaria rhynchophylla and Characterization of the Critical Enzyme Involved in the Biosynthesis of Bioactive Compounds-(iso)Rhynchophylline.

Rhynchophylline (RIN) and isorhynchophylline (IRN), two of the representative types of indole alkaloids, showed the unique spiroindole structures produced in Uncaria rhynchophylla. As the bioactive constituent of U. rhynchophylla, IRN has recently drawn extensive attention toward antihypertensive and neuroprotective activities. Despite their medicinal importance and unique chemical structure, the biosynthetic pathways of plant spiroindole alkaloids are still largely unknown. In this study, we used U. rhynchophylla, extensively used in traditional Chinese medicine (TCM), a widely cultivated plant of the Uncaria genus, to investigate the biosynthetic genes and characterize the functional enzymes in the spiroindole alkaloids. We aim to use the transcriptome platform to analyse the tissue-specific gene expression in spiroindole alkaloids-producing tissues, including root, bud, stem bark and leaf. The critical genes involved in the biosynthesis of precursors and scaffold formation of spiroindole alkaloids were discovered and characterized. The datasets from this work provide an essential resource for further investigating metabolic pathways in U. rhynchophylla and facilitate novel functional enzyme characterization and a good biopharming approach to spiroindole alkaloids.

Combinatorial biosynthesis yields novel hybrid argimycin P alkaloids with diverse scaffolds in Streptomyces argillaceus.

Coelimycin P1 and argimycins P are two types of polyketide alkaloids produced by Streptomyces coelicolor and Streptomyces argillaceus, respectively. Their biosynthesis pathways share some early steps that render very similar aminated polyketide chains, diverging the pathways afterwards. By expressing the putative isomerase cpkE and/or the putative epoxidase/dehydrogenase cpkD from the coelimycin P1 gene cluster into S. argillaceus wild type and in argimycin mutant strains, five novel hybrid argimycins were generated. Chemical characterization of those compounds revealed that four of them show unprecedented scaffolds (quinolizidine and pyranopyridine) never found before in the argimycin family of compounds. One of these compounds (argimycin DM104) shows improved antibiotic activity. Noticeable, biosynthesis of these quinolizidine argimycins results from a hybrid pathway created by combining enzymes from two different pathways, which utilizes an aminated polyketide chain as precursor instead of lysine as it occurs for other quinolizidines.

Comparative Pharmacokinetic Study of Two Pyrrolizidine Alkaloids Lasiocarpine and Heliotrine in Rats.

Lasiocarpine (LAS) and heliotrine (HEL) are two different ester types of toxic pyrrolizidine alkaloids (PAs): open-chain diester and monoester. However, the pharmacokinetics of these two types of PAs in rats have not been reported. In the present study, two LC-MS/MS methods for determining LAS and HEL were established and validated. The methods exhibited good linearity, accuracy, and precision and were then applied to a comparative pharmacokinetic study. After intravenous administration to male rats at 1 mg/kg, the AUC0-t values of LAS and HEL were 336 ± 26 ng/mL × h and 170 ± 5 ng/mL × h. After oral administration at 10 mg/kg, the AUC0-t of LAS was much lower than that of HEL (18.2 ± 3.8 ng/mL × h vs. 396 ± 18 ng/mL × h), while the Cmax of LAS was lower than that of HEL (51.7 ± 22.5 ng/mL × h vs. 320 ± 26 ng/mL × h). The absolute oral bioavailability of LAS was 0.5%, which was significantly lower than that of HEL (23.3%). The results revealed that the pharmacokinetic behaviors of LAS differed from that of HEL.