Les pathosystèmes, plante-bactérie, aboutissent souvent au niveau de la plante à de profondes reprogrammations tant au niveau de la morphogenèse que du métabolome. Dans le cas de l’interaction plante-Rhodococcus fascians, une bactérie phytopathogène, il se développe au niveau du site d’infection, une structure morphologique particulière nommée « galle feuillée ». <p>Au sein de cette hyperplasie, les altérations métaboliques induites concernent non seulement les produits du métabolisme primaire mais également le métabolisme secondaire et plus particulièrement des composés qui interviennent dans les mécanismes de défense ou qui affectent la prolifération cellulaire végétale. <p>Dans le cadre de notre travail de thèse, nous nous sommes fixé deux objectifs principaux qui sont de caractériser les altérations métaboliques au niveau des tissus hyperplasiques de tabac mais aussi de rechercher des applications potentielles du point de vue thérapeutique de cette interaction.<p>L’approche métabolomique globale basée sur une analyse comparative des spectres 1H-RMN d’extraits bruts de tissus infectés et de tissus non-infectés couplée à des analyses statistiques de données multivariées (ACP, OPLS-DA) a été utilisé pour l’étude de la reprogrammation métabolique. Le résultat indique une accumulation de composés phénoliques et des métabolites de la famille des diterpènes dans les tissus de la galle feuillée. <p>Les activités biologiques des extraits de la galle feuillée ont ensuite été évaluées, notamment des activités antioxydantes (DPPH, FRAP), anti-inflammatoire (15-LOX) et antiproliférative (MTT). Il ressort de cette analyse une augmentation du potentiel réducteur et anti-radicalaire des extraits de la galle feuillée, une activité inhibitrice de la lipoxygénase ainsi qu'une activité antiproliférative sur lignées tumorales humaines, comparée à la plante non infectée. <p>L’étude des composés affectant la prolifération des cellules cancéreuses humaines a aboutit à la mise en évidence d’un mélange de molécules (F3.1.1) appartenant au groupe des incensoles (cembrènoïdes). Ces composés ralentissent la durée de la division cellulaire, affectent la taille des cellules et induisent des anomalies de la karyokinèse et de la cytokinèse des cellules de glioblastome U373. La dynamique tubuline/microtubule est identifiée comme étant la cible des cembrènoïdes (F3.1.1). L’effet des ces composés est original comparé aux anti-tubulines usuels tel que la colchicine et le paclitaxel. Le mécanisme d’action des incensoles est unique et donc prometteur du fait que la dynamique des microtubules reste une cible de choix dans le traitement des cellules cancéreuses.<p> / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished

The progressive increase in the global population and the rapidly changing climate have put unprecedented pressure on crop production. Cowpea is one of the world’s most important leguminous crops, contributing to food security and environmental sustainability. However, cowpea productivity is limited due to waterlogging stress. The main objective of this study was to explore physiological and biochemical mechanisms to understand how cowpea genotypes respond to waterlogging stress. Four studies were conducted in controlled and field conditions to achieve these objectives. Study 1 characterized the waterlogging tolerance of 30 cowpea genotypes in a controlled environment using 24 morphophysiological parameters with waterlogging tolerance coefficients and multivariate analysis methods. 10% of the genotypes exhibited high tolerance to waterlogging stress, and the genotypes UCR 369 and EpicSelect.4 were identified as the most and least waterlogging tolerant, respectively. Study 2 evaluated the key parameters influencing carbon fixation of UCR 369 and EpicSelect.4 at the reproductive stage. The less tolerant EpicSelect.4 experienced high downregulation of stomatal and non-stomatal limiting factors during waterlogging and recovery, resulting in decreased carbon assimilation rates. UCR 369 rapidly developed adventitious roots, maintained biomass, and restored pigments and metabolites to sustain photosynthesis. A two-year field experiment was conducted in study 3 to quantify the effects of waterlogging on the yields, physiology, and biochemistry of cowpeas at different growth stages. The most apparent impact of waterlogging stress occurred at the reproductive stage, followed by the vegetative and maturity growth stages. Studies suggest that diverse cowpea genotypes have distinct physiological and biochemical mechanisms in response to waterlogging stress. In addition, the tolerant genotypes and traits identified herein can be used in genetic engineering and cowpea breeding programs that integrate increased yield with waterlogging stress tolerance.

In 2004, the polyketide natural product, chamuvarinin (72) was isolated by Laurens et al. from the roots of Uvaria chamae, a member of the Annonaceae plant family. This unique tetrahydropyran containing acetogenin displayed potent levels of cytotoxic activity against the KB 3-1 cell line with an ED50 value of 0.8 nM. Upon initial isolation the relative and absolute stereochemical assignment of chamuvarinin (72) was unable to be readily achieved through ¹H and ¹³C NMR analysis. The initial synthetic route described herein has enabled the relative and absolute stereochemical determination of chamuvarinin (72) through the first total synthesis completed in 20 longest linear steps in 1.5% overall yield. A revised synthetic strategy towards chamuvarinin (72) was completed in 17 longest linear steps in 2.2% overall yield. The revised route facilitated the assembly of non-natural chamuvarinin-like analogues and their trypanocidal and cytotoxic activities have been assessed. The synthesis of these analogues has formed the basis of a more focussed study through the design and synthesis of simplified triazole (295), isoxazole (325) and butenolide triazole (305) analogues as potential Trypanosoma brucei (causative agent in African Sleeping sickness) inhibitors.

Sclerocarya birrea (marula, Anacardiaceae) is a highly-valued indigenous tree in most parts of sub-Saharan Africa because of its medicinal and nutritional properties. The marula tree is adapted to the semi-arid conditions that characterise most parts of sub-Saharan Africa and renders them unsuitable for conventional crop agriculture. The unique nutritional properties of marula and its high tolerance to dry conditions provide opportunities for its development into a plantation crop. On the other hand, the demand for marula plant parts, mainly the bark and roots as medicinal remedies, poses a great threat to wild populations. In the long term, the growing demand of marula products in the food, pharmaceutical and cosmetic industries will not be sustainable from wild populations alone. Plant tissue culture technologies can be useful for in vitro manipulation and mass propagation of the plant in the process of domestication and conservation. The aims of the project were to determine the optimum conditions for seed germination, in vitro propagation and plant regeneration, and to evaluate the potential bioactivity of secondary metabolites from its renewable plant parts as an alternative option in the conservation of S. birrea. An ex vitro seed germination study indicated that after-ripening and cold stratification are critical factors. Cold stratification (5 °C) of marula nuts for 14 days improved germination (65%) as compared to non-stratified nuts (32%). Direct shoot organogenesis was achieved from leaf explants through the induction of nodular meristemoids on Murashige and Skoog (MS) (1962) medium and woody plant medium (WPM) supplemented with 6-benzyladenine (BA) in combination with naphthalene acetic acid (NAA), indole-3-butryric acid (IBA) and indole-3-acetic acid (IAA). Induction of nodular meristemoids from 86% of the leaf cultures was achieved on a MS medium with 4.0 ìM BA and 1.0 ìM NAA. High levels (78–100%) of induction were also achieved on WPM with different concentrations of BA (1.0–4.0 ìM) and IBA (1.0–4.0 ìM). The highest conversion of nodular meristemoids into shoots on MS initiation medium was only 22% for 4.0 ìM BA and 1.0 ìM NAA. This was improved to 62% when nodular clusters were cultured in MS liquid medium. Histological studies revealed high numbers of unipolar meristematic buds developing from globular nodules. These embryo-like structures have in the past been mistaken for true somatic embryos. The initiation of high numbers of nodular meristemoids per explant provides potential for automated large-scale clonal propagation in bioreactors, in vitro phytochemical production and the development of synthetic seed technology, similar to somatic embryogenesis. Plant regeneration through nodule culture has potential for application in mass micropropagation and plant breeding of S. birrea. Adventitious shoot and root induction are important phases in micropropagation. Plant growth regulators play an important role in these developmental processes, and the type and concentration used have major influences on the eventual organogenic pathway. Three auxins (IAA, IBA and NAA) and four aromatic cytokinins (6-benzyladenine, meta-topolin, meta-topolin riboside, and meta-methoxytopolin riboside) were evaluated for their potential to induce adventitious shoot and root formation in S. birrea shoots, hypocotyls and epicotyls. Among the evaluated cytokinins, the highest adventitious shoot induction (62%) was achieved on MS medium supplemented with meta-topolin (8.0 ìM). The lowest adventitious shoot induction (2.5%) was obtained on MS basal medium containing 2.0 ìM meta-methoxytopolin riboside. The highest adventitious shoot induction for hypocotyls was 55% on MS medium supplemented with 8.0 ìM meta-topolin. For the tested auxins, IBA induced adventitious rooting in 91% of shoots at a concentration of 4.0 ìM after 8 weeks in culture. However, the in vitro rooted plants only survived for two weeks when transferred ex vitro. A temperature of 25 °C and 16-h photoperiod were optimum for adventitious root induction. Stomatal density (number per mm2) on the abaxial leaf surfaces was higher for the 16-h photoperiod treatment (206.6 ± 15.28) compared to that for a 24-h photoperiod (134.6 ± 12.98). Normal mature stomata with kidney-shaped guard cells and an outer ledge over the stomatal pore were observed for in vitro plants growing under a 16-h photoperiod. Total phenolic content, proanthocyanidins, gallotannins, flavonoids, and antioxidant activities of S. birrea methanolic extracts were evaluated using in vitro bioassays. Methanolic extracts of the young stem bark and leaves contained high levels of these phytochemicals. Sclerocarya birrea young stem extracts contained the highest levels of total phenolics (14.15 ± 0.03 mg GAE g-1), flavonoids (1219.39 ± 16.62 ìg CE g-1) and gallotannins (246.12 ± 3.76 ìg GAE g-1). Sclerocarya birrea leaf extracts had the highest concentration of proanthocyanidins (1.25%). The EC50 values of the extracts in the DPPH free radical scavenging assay ranged from 5.028 to 6.921 ìg ml-1, compared to ascorbic acid (6.868 ìg ml-1). A dose-dependent linear curve was obtained for all extracts in the ferric-reducing power assay. All the extracts exhibited high antioxidant activity comparable to butylated hydroxytoluene based on the rate of â-carotene bleaching (89.6 to 93.9%). Sclerocarya birrea provides a source of secondary metabolites which have potent antioxidant properties and may be beneficial to the health of consumers. Sclerocarya birrea young stem and leaf ethanolic extracts exhibited high bioactivity (MIC < 1.0 mg ml-1) against both Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacteria. The highest activity (MIC = 0.098 mg ml-1 and total activity = 1609.1 ml g-1) was recorded for young stem extracts against B. subtilis. The highest activity (MIC = 1.56 mg ml-1 and MFC = 1.56 mg ml-1) in the antifungal assay against Candida albicans was observed for young stem ethanolic extracts. Sclerocarya birrea extracts had moderate acetylcholinesterase (AChE) inhibition activity. The dichloromethane (DCM) and methanol (MeOH) fractions exhibited dose-dependent acetylcholinesterase inhibitory activity. The highest AChE inhibitory activities were from leaves (DCM fraction, IC50 = 0.1053 mg ml-1) and young stems (MeOH fraction, IC50 = 0.478 mg ml-1). High inhibitory activity against cyclooxygenase (COX-1 and COX-2) enzymes was observed. All extracts and fractions showed high COX-1 enzyme inhibition (90.7-100%). Petroleum ether (PE) and dichloromethane fractions also exhibited high inhibition against COX-2 enzyme (77.7-92.6%). The pharmacological activities observed suggest that S. birrea renewable plant parts (leaves and young stems) provide a substantial source of medicinal secondary metabolites. Based on these results, plant part substitution can be a practical conservation strategy for this species. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-06-22T11:07:10Z No. of bitstreams: 1 michelledelimadetoni.pdf: 1224744 bytes, checksum: a3734f99b34853e12e12fb5964be66e5 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-07T19:20:05Z (GMT) No. of bitstreams: 1 michelledelimadetoni.pdf: 1224744 bytes, checksum: a3734f99b34853e12e12fb5964be66e5 (MD5) / Made available in DSpace on 2017-08-07T19:20:05Z (GMT). No. of bitstreams: 1 michelledelimadetoni.pdf: 1224744 bytes, checksum: a3734f99b34853e12e12fb5964be66e5 (MD5) Previous issue date: 2009-03-06 / FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais / Calliandra brevipes apresenta uma galha globosa (GG) e uma fusiforme (GF), induzidas por Tanaostigmodes mecanga e T. ringueleti, respectivamente. As variações sazonais no conteúdo fenólico de ambas as galhas, de caule e folha não galhados (CS e FS, respectivamente) foram analisadas durante 12 meses. O perfil de variação do teor fenólico nos tecidos galhados e não galhados de C. brevipes foi similar ao longo do período analisado, apresentando-se fortemente influenciado pelas variações na precipitação pluviométrica, ocorrendo maior acúmulo fenólico quando o vegetal estava sob estresse hídrico. Os conteúdos fenólicos de ambas as galhas foram similares e, no período de drásticas mudanças na precipitação pluviométrica, estes sofreram alterações significativamente menores do que as sofridas pelos tecidos não galhados, sugerindo que as duas espécies de Tanaostigmodes modulam o conteúdo fenólico no tecido galhado de maneira similar. Assim, notou-se que as alterações no conteúdo fenólico podem estar primariamente associadas às mudanças pluviométricas, constituindo uma defesa direta contra o estresse hídrico. Na triagem de metabólitos secundários, flavonóides, cumarinas e taninos foram detectados em tecidos galhados e não galhados de C. brevipes. Saponinas foram encontradas somente em amostras de tecidos não galhado, mostrando que as galhas apresentam menor toxicidade para o herbívoro. Triterpenóides foram encontrados em GG e esteróides em GF, sugerindo que cada galhador explora diferencialmente o metabolismo do hospedeiro. Adicionalmente, o conteúdo de flavonóides e a atividade antioxidante também estavam diferenciados em ambas as galhas, sendo maiores na galha fusiforme. Na análise cromatográfica e densitométrica de carboidratos, GG e GF apresentaram conteúdos de sacarose, glicose e frutose maiores do que os encontrados em tecidos não galhados, 1,5-3 vezes e 2 vezes, respectivamente. A análise de saponinas e carboidratos evidenciou que ambas as galhas apresentam menor toxicidade e constituem uma fonte mais nutritiva para o herbívoro do que o tecido não galhado. O fracionamento e a análise densitométrica de proteínas, detectou polipeptídeos comuns a ambas as galhas (80, 69, 61, 52, 32 kDa) provavelmente essenciais para a organização básica desta neoformação, bem como específicos a cada uma (galha globosa: 97, 75, 34 kDa; galha fusiforme: 40, 33 kDa) que podem estar associadas aos distintos morfotipos e suas vias metabólicas. Em conjunto, a análise de proteínas, flavonóides e a atividade antioxidante mostram que cada galhador manipula o hospedeiro de maneira peculiar, mesmo quando duas espécies galhadoras filogeneticamente tão próximas parasitam um hospedeiro comum. Quanto à análise fosfohidrolítica, CS hidrolisou igualmente ATP, ADP, UDP ou GDP. Na GG, o UDP, GDP, e ADP foram hidrolisados aproximadamente 1,5-3 vezes mais do que no CS, já o AMP foi 10 vezes mais hidrolisado na GG. Em conjunto, estes dados confirmam que este tecido exacerba os mecanismos capazes de hidrolisar nucleotídeos, possivelmente devido sua maior atividade metabólica. Atividades ADPásica e UDPásica de CS e GG foram 10-32% estimuladas por 5 mM de Ca2+, e inibidas pela adição de 5 mM EDTA ou EGTA (88 a 100%), confirmando a dependência destas atividades à cátions bivalentes. Uma pequena inibição por ortovanadato foi detectada sugerindo a presença de P-ATPases, enquanto azida sódica, DCCD e bafilomicina não inibiram significativamente a atividade ATPásica. Uma apirase de 75 kDa foi identificada em CS e GG de C. brevipes, e provavelmente contribuiu com a atividade fosfohidrolítica observada. Foi constatada a presença de apirase e de atividade ADPásica nas células nutritivas que delineiam a câmara larvar por microscopia de imunofluorescência e citoquímica, respectivamente. A alta atividade apirásica na galha globosa de C. brevipes pode estar associada à biossíntese de carboidratos, recuperação de nucleosídeos e/ou proliferação celular, contribuindo assim, para a nutrição e sobrevivência do galhador. / Calliandra brevipes presents globose (GG) and fusiform galls (GF) induced by Tanaostigmodes mecanga and T. ringueleti, respectively. The seasonal changes in phenolic content of both galls, and in non-galled stem and leaf were analyzed over one year. The phenolic variation profile of galled or non-galled tissues of C. brevipes was similar during the analyzed period, but it is strongly influenced by the variations in the pluviometric levels increasing during hydric stress. The phenolic levels were in similar amounts between the two galls and, in the period of drastic changes in pluviometric levels, the alterations were significantly higher in non-galled tissues when compared to the galled tissues, suggesting that the two distinct species of Tanaostigmodes manipulate the phenolic level in a similar way. Therefore, the alterations in phenolic contents could be primarily associated to the pluviometric changes, constituting a direct defense against the hydric stress. The phytochemical screening showed the presence of flavonoids, coumarins and tannins in galled and non-galled samples. Saponins were found only in non-galled samples, suggesting that the galled tissues are less toxic to the herbivory. Triterpenoids were detected in GG, but not in GF, suggesting that each inducer explore in a different way the plant metabolism. In addition, flavonoids content and antioxidant activity were differentiated in both galls, being significantly higher in fusiform gall. Chromatographic and densitometric analyses showed that GG and GF present sucrose, glucose and fructose contents 1.5-3 and 2 times higher, respectively than those found in non galled tissue. The secondary metabolites and carbohydrate analyses evidenced that both galls tissues are less toxic and constitute a better nutrient source for the herbivory than the non-galled tissues. Protein fractionation and densitometric analysis showed common polypeptides to both galls (80, 69, 61, 52, 32 kDa) possibly essentials for their basic neoformations, and specific polypeptides in either globose (globose: 97, 75, 34 kDa) or fusiform gall (40, 33 kDa), which could be associated to the different gall morphotypes and their metabolic pathways. Together, the protein, flavonoid and antioxidant analyses showed that each inducer, although closer phylogenetically, manipulate the host by specific pathways in the same plant. Phosphohydrolitic analysis showed that CS equally hydrolyzed either ATP, ADP, UDP or GDP. In GG, the UDP, GDP, and ADP were hydrolyzed approximately 1.5-3 folds higher than that found in CS. AMP hydrolyzes was 10 folds higher in GG confirming that this tissue increase their mechanisms capable of hydrolyzing nucleotides. ADPase and UDPase activities from CS and GG were 10-32% stimulated by 5 mM calcium, and inhibited by the addition of 5 mM EDTA or EGTA (88 to 100%), thus confirming the divalent cation dependence. Little ATPase inhibition by orthovanadate was detected suggesting the presence of a P-type ATPase, while sodium azide, dicyclohexylcarbodiimide, and bafilomycin did not affect significantly the ATPase activity. A band of 75 kDa was recognized by polyclonal anti-potato apyrase antibodies in CS or GG, confirming the presence of an apyrase in Calliandra brevipes. By immunofluorescence microscopy, using anti-potato apyrase antibodies, and by cytochemical techniques, using ADP as substrate, the apyrase was located on the external surface and inside of the nutritive cells that compose the central chamber. The high apyrase activity in globose gall of C. brevipes could be participating in carbohydrate biosynthesis, in the salvage pathway of nucleosides and/or cell proliferation, for the feeding and survival of the insect.

Flavonoids are a class of plant metabolites with a C6-C3-C6 structure. They are responsible for a large range of biological functions including UV protection, pigmentation, and anti-microbial properties. Citrus paradisi, the grapefruit, contains a wide variety of flavonoids, including the target flavonols which are characterized by a hydroxyl group at the C3 position. A glucose molecule is added to flavonols by 3-Oglucosyltransferases (3-O-GTs). C. paradisi F3-O-GT only glucosylates flavonols; however, Vitis vinifera (grape) 3-O-GT can accept both flavonols and anthocyanidins. The two enzymes have some identity with one another but sequence alignment pinpointed several areas of non-homology. Homology modeling using the crystallized structure of the V. vinifera 3-GT revealed sites within the non-homologous areas that could influence the binding site most directly. The 382 site was of particular interest with arginine in C. paradisi changed to tryptophan in V. vinifera, a much bulkier and non-charged amino acid. Site-directed mutagenis was performed to form the R382W mutant line and transformed into yeast for expression after induction with methanol. Western blot was used to determine the optimal protein induction time, after which the cells were harvested and broken to extract the proteins. Isolation and purification of the protein in question allows for enzyme analysis. This is performed by measuring incorporation of radioactive glucose onto various substrates from each flavonoid class. High counts indicate that the enzyme is active upon the substrate while low counts indicate little to no activity. Characterization will also be performed by varying reaction conditions. Thus, the optimal pH, temperature, substrate quantity, enzyme quantity, and reaction duration can be determined for this specific mutant. These experiments will determine if the R382W mutation has a significant impact on the substrate specificity or reaction conditions for the enzyme. A change in activity to include other classes of flavonoids besides flavonols indicates that the mutation site has a direct impact on the conformation of the binding site. Failure of the mutation to change substrate specificity still provides valuable information for the structure and function of the enzyme. This has implications for engineering enzymes to perform specific functions.

No description available.

Department of Chemistry / PhD (Chemistry) / This thesis is concerned with the computational study of naphthylisoquinoline alkaloids having antimalarial properties. The study was considered interesting because of the importance of gathering information on antimalarial molecules and because these molecules had not yet been studied computationally. The alkaloids considered in this study had been isolated from tropical lianas belonging to the Dioncophyllaceae and Ancistrodaceae families. They comprise alkaloids with both monomeric and dimeric structures. The monomeric structures consist of one unit and the dimeric ones of two units, with each unit containing a naphthalene moiety and an isoquinoline moiety. 33 monomeric molecules were studied, which represent a large portion of all the monomeric naphthylisoquinoline alkaloids isolated so far. Two dimeric molecules with antimalarial activity were investigated, namely, jozimine A2 and mbandakamine A. A third dimeric molecule, with a structure close to that of jozimine A2 but different activity (michellamine A, anti-HIV) was also calculated for comparison purposes. This work utilised electronic structures methods and involved the conformational study of all the molecules selected to identify the stabilising factors in vacuo and in solution. Two levels of theory (HF/ 6-31G (d,p) and DFT/B3LYP/ 6-31+G(d,p)) were utilised to compare their performance for compounds of this type, also in view of a future study extending to other compounds of the same class. The molecules were firstly studied in vacuo and secondly in three different solvents – chloroform, acetonitrile and water – characterized by different polarities and different H-bonding abilities. Quantum chemical calculations in solution were carried out using the Polarisable Continuum Model (PCM). The main stabilizing factors are the presence and types of intramolecular hydrogen bonds (IHBs), which are the dominant factors, and also the mutual orientation of the moieties. The possible IHBs comprise OH⋯O (or OH⋯N and NH⋯O for mbandakamine A) and other H-bond types interactions such as OH⋯ and CH⋯O (or CH⋯O and CH⋯N for mbandakamine A). The moieties prefer to be perpendicular one to another, which is a common tendency of aromatic vii systems. In monomeric structures, there may be only one OH⋯O and possibly also one of each of the other two types of IHBs interactions. In dimeric structures, there may be up to four (five in mbandakamine A) OH⋯O IHBs simultaneously and also other H-bond type interactions. The results provide a comprehensive picture of the molecular properties of these compounds, such as conformational preferences, dipole moments, HOMO-LUMO energy gaps, harmonic vibrational frequencies, solvent effect and influence of the solvent on molecular properties which respond to polarisation by the solvent. Altogether, these results may contribute to a better understanding of their biological activity and to the design of molecular structures with enhanced biological activity. This is the reason of focusing the efforts on the investigation of chemical and physical properties of these alkaloids molecules. / NRF

(1) Background: Members of the TRPC3/TRPC6/TRPC7 subfamily of canonical transient receptor potential (TRP) channels share an amino acid similarity of more than 80% and can form heteromeric channel complexes. They are directly gated by diacylglycerols in a protein kinase C-independent manner. To assess TRPC3 channel functions without concomitant protein kinase C activation, direct activators are highly desirable. (2) Methods: By screening 2000 bioactive compounds in a Ca2+ influx assay, we identified artemisinin as a TRPC3 activator. Validation and characterization of the hit was performed by applying fluorometric Ca2+ influx assays and electrophysiological patch-clamp experiments in heterologously or endogenously TRPC3-expressing cells. (3) Results: Artemisinin elicited Ca2+ entry through TRPC3 or heteromeric TRPC3:TRPC6 channels, but did not or only weakly activated TRPC6 and TRPC7. Electrophysiological recordings confirmed the reversible and repeatable TRPC3 activation by artemisinin that was inhibited by established TRPC3 channel blockers. Rectification properties and reversal potentials were similar to those observed after stimulation with a diacylglycerol mimic, indicating that artemisinin induces a similar active state as the physiological activator. In rat pheochromocytoma PC12 cells that endogenously express TRPC3, artemisinin induced a Ca2+ influx and TRPC3-like currents. (4) Conclusions: Our findings identify artemisinin as a new biologically active entity to activate recombinant or native TRPC3-bearing channel complexes in a membrane-confined fashion.