Artemisinin-based antimalarial research: application of biotechnology to the production of artemisinin, its mode of action, and the mechanism of resistance of Plasmodium parasites

Alternative first-line malaria treatment

Malaria is a disease affecting millions of people, especially in Africa, Asia, and South America, and has become a substantial economic burden. Because malaria is contracted through the bite of a mosquito vector, it is very challenging to prevent. Bed nets and insect repellents are used in some homes; others do not have or use them even when available. Thus, treatment measures are crucial to controlling this disease. Artemisinin-based combination therapy (ACT) is currently the first-line treatment for malaria. ACT has been used for decades, but recently, there has been evidence of potential resistance. This threat of resistance has led to the search for possible alternatives to ACT. In sub-Saharan Africa, Azadirachta indica, or simply neem, is a plant used to treat a variety of ailments, including malaria. Neem is effective against one of the more deadly malaria parasites Plasmodium falciparum. Reports show that neem inhibits microgametogenesis of P. falciparum and interferes with the parasite's ookinete development. Although there is substantial in vitro research on the biological activity of A. indica (neem), there is limited in vivo research. Herein, we discuss the in vivo effects of neem on malaria parasites. With A. indica, the future of malaria treatment is promising, especially for high-risk patients, but further research and clinical trials are required to confirm its biological activity.

Bacterial Membrane Vesicles for In Vitro Catalysis

The use of biological systems in manufacturing and medical applications has seen a dramatic rise in recent years as scientists and engineers have gained a greater understanding of both the strengths and limitations of biological systems. Biomanufacturing, or the use of biology for the production of biomolecules, chemical precursors, and others, is one particular area on the rise as enzymatic systems have been shown to be highly advantageous in limiting the need for harsh chemical processes and the formation of toxic products. Unfortunately, biological production of some products can be limited due to their toxic nature or reduced reaction efficiency due to competing metabolic pathways. In nature, microbes often secrete enzymes directly into the environment or encapsulate them within membrane vesicles to allow catalysis to occur outside the cell for the purpose of environmental conditioning, nutrient acquisition, or community interactions. Of particular interest to biotechnology applications, researchers have shown that membrane vesicle encapsulation often confers improved stability, solvent tolerance, and other benefits that are highly conducive to industrial manufacturing practices. While still an emerging field, this review will provide an introduction to biocatalysis and bacterial membrane vesicles, highlight the use of vesicles in catalytic processes in nature, describe successes of engineering vesicle/enzyme systems for biocatalysis, and end with a perspective on future directions, using selected examples to illustrate these systems' potential as an enabling tool for biotechnology and biomanufacturing.

Ethnomedicinal plants used for malaria treatment in Rukungiri District, Western Uganda

BACKGROUND

Malaria remains a major global health challenge and a serious cause of morbidity and mortality in sub-Saharan Africa. In Uganda, limited access to medical facilities has perpetuated the reliance of indigenous communities on herbal medicine for the prevention and management of malaria. This study was undertaken to document ethnobotanical knowledge on medicinal plants prescribed for managing malaria in Rukungiri District, a meso-endemic malaria region of Western Uganda.

METHODS

An ethnobotanical survey was carried out between May 2022 and December 2022 in Bwambara Sub-County, Rukungiri District, Western Uganda using semi-structured questionnaire. A total of 125 respondents (81 females and 44 males) were randomly selected and seven (7) key informants were engaged in open interviews. In all cases, awareness of herbalists on malaria, treatment-seeking behaviour and herbal treatment practices were obtained. The ethnobotanical data were analyzed using descriptive statistics, informant consensus factor and preference ranking.

RESULTS

The study identified 48 medicinal plants belonging to 47 genera and 23 families used in the treatment of malaria and its symptoms in the study area. The most frequently cited species were Vernonia amygdalina, Aloe vera and Azadirachta indica. Leaves (74%) was the most used plant organ, mostly for preparation of decoctions (41.8%) and infusions (23.6%) which are administered orally (89.6%) or used for bathing (10.4%).

CONCLUSIONS

Indigenous knowledge of medicinal plants used as prophylaxis and for treatment of malaria still exist among the local communities of Bwambara Sub-County. However, there is a need to investigate the antimalarial efficacy, phytochemical composition and safety of species (such as Digitaria abyssinica and Berkheya barbata) with high percentage use values to validate their use.

Medicinal plants used for treatment of malaria by indigenous communities of Tororo District, Eastern Uganda

BACKGROUND

Malaria remains the leading cause of death in sub-Saharan Africa. Although recent developments such as malaria vaccine trials inspire optimism, the search for novel antimalarial drugs is urgently needed to control the mounting resistance of Plasmodium species to the available therapies. The present study was conducted to document ethnobotanical knowledge on the plants used to treat symptoms of malaria in Tororo district, a malaria-endemic region of Eastern Uganda.

METHODS

An ethnobotanical study was carried out between February 2020 and September 2020 in 12 randomly selected villages of Tororo district. In total, 151 respondents (21 herbalists and 130 non-herbalists) were selected using multistage random sampling method. Their awareness of malaria, treatment-seeking behaviour and herbal treatment practices were obtained using semi-structured questionnaires and focus group discussions. Data were analysed using descriptive statistics, paired comparison, preference ranking and informant consensus factor.

RESULTS

A total of 45 plant species belonging to 26 families and 44 genera were used in the preparation of herbal medicines for management of malaria and its symptoms. The most frequently mentioned plant species were Vernonia amygdalina, Chamaecrista nigricans, Aloe nobilis, Warburgia ugandensis, Abrus precatorius, Kedrostis foetidissima, Senna occidentalis, Azadirachta indica and Mangifera indica. Leaves (67.3%) were the most used plant part while maceration (56%) was the major method of herbal remedy preparation. Oral route was the predominant mode of administration with inconsistencies in the posology prescribed.

CONCLUSION

This study showed that the identified medicinal plants in Tororo district, Uganda, are potential sources of new antimalarial drugs. This provides a basis for investigating the antimalarial efficacy, phytochemistry and toxicity of the unstudied species with high percentage use values to validate their use in the management of malaria.

Transcriptional regulatory network of high-value active ingredients in medicinal plants

High-value active ingredients in medicinal plants have attracted research attention because of their benefits for human health, such as the antimalarial artemisinin, anticardiovascular disease tanshinones, and anticancer Taxol and vinblastine. Here, we review how hormones and environmental factors promote the accumulation of active ingredients, thereby providing a strategy to produce high-value drugs at a low cost. Focusing on major hormone signaling events and environmental factors, we review the transcriptional regulatory network mediating biosynthesis of representative active ingredients. In this network, many transcription factors (TFs) simultaneously control multiple synthase genes; thus, understanding the molecular mechanisms affecting transcriptional regulation of active ingredients will be crucial to developing new breeding possibilities.

Dihydroartemisinin imposes positive and negative regulation on Treg and plasma cells via direct interaction and activation of c-Fos

Dihydroartemisinin (DHA), a potent antimalarial drug, also exhibits distinct property in modulation on T_reg and B cells, which has been recognized for decades, but the underlying mechanisms remain understood. Herein we revealed that DHA could promote T_reg proliferation, meanwhile, suppress B cell expansion in germinal centers, and consequently decrease the number of circulating plasma cells and the content of serum immunoglobulins. Further, DHA-activated T_reg significantly mitigated lipopolysaccharide-induced and malaria-associated inflammation. All these scenarios were attributed to the upregulation of c-Fos expression by DHA and enhancement of its interaction with target genes in both T_reg and circulating plasma cells with bilateral cell fates. In T_reg, the c-Fos-DHA complex upregulated cell proliferation-associated genes and promoted cell expansion; whereas in plasma cells, it upregulated the apoptosis-related genes resulting in decreased circulating plasma cells. Thus, the bilateral immunoregulatory mechanism of DHA was elucidated and its application in the treatment of autoimmune diseases is further justified.

Molecular insights into the genetic diversity and population structure of Artemisia annua L. as revealed by insertional polymorphisms

The knowledge about the level of genetic diversity and population structure in natural populations of Artemisia annua L. is a primary step in breeding programs for development of new cultivars with higher artemisinin level and better quality of secondary metabolites composition. We used PCR-based "retrotransposon-microsatellite amplified polymorphisms" (REMAPs) to study insertional polymorphism in A. annua genome to assess genetic variability and population structure in a collection of 118 accessions collected from north and northwest of Iran. Twenty-five primer combinations of 10 retrotransposon and seven ISSR primers amplified a total of 693 clear and unambiguous fragments in the studied accessions. The average number of bands, polymorphic bands, polymorphism, effective number of alleles, Shannon's information index and expected heterozygosity were 27.72, 24.76, 88.14%, 1.47, 0.42 and 0.28, respectively. The analysis of molecular variance revealed high genetic variation present within sampled geographical regions. Distance-based cluster analysis assigned the studied accessions into four clusters according to their geographical origin, which were also confirmed by principal coordinate analysis. In model-based Bayesian clustering, the maximum value of Δk was obtained when the collection of 118 assayed A. annua accessions assigned into two subgroups (K = 2). The results showed the high genetic variation in the collection of Iranian sweet wormwood which revealed by REMAP markers indicating the reliability and efficiency of this marker system for analysis of genetic diversity and population structure of A. annua.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40415-022-00860-x.

Aging affects artemisinin synthesis in Artemisia annua

Artemisinin (ART) is the most effective component in malaria treatment, however, the extremely low content restricts its clinical application. Therefore, it is urgent to increase the yield of ART. ART gradually accumulates with aging, small RNA (sRNA) and transcriptome analysis were applied on the leaves of 2-week-old (2 w) and 3-month-old (3 m) A. annua respectively. Among all the annotated sRNAs, 125 were upregulated and 128 downregulated in the 3 m sample compared to the 2 w one. Whereas 2183 genes were upregulated and 2156 downregulated. Notably, the level of miR156 and several annotated miRNAs gradually decreased while SPLs increased. In addition, the genes on ART biosynthesis pathway were significantly upregulated including ADS, CYP71AV1, ADH1, DBR2 and ALDH1, and so were the positive transcription factors like AaERF1, AaORA and AaWRKY1 indicating that age influences the ART biosynthesis by activating the expression of the synthesizing genes as well as positive transcription factors. This study contributes to reveal the regulatory effects of age on ART biosynthesis both in sRNA and transcription levels.

Artemisinin Activity in Red Blood Cells from Anemic Children

Artemisinin combination therapies are the current frontline therapy for falciparum malaria. Artemisinin is activated by heme iron, and the consequent production of reactive oxygen species and carbon-centered radicals results in rapid parasite clearance. Red blood cells (RBCs) from anemic iron-deficient individuals have decreased levels of heme, and such deficiencies are highly prevalent among children and pregnant women in malaria-endemic countries. We, therefore, investigated the possibility that host anemia could impair artemisinin activity and alter the drug sensitivity of artemisinin-resistant strains of Plasmodium falciparum. We collected RBCs from anemic (n = 35) and nonanemic (n = 11) Gambian children between the ages of 2 and 24 months. Parasites grown in RBCs from both groups were assessed in vitro using the ring-stage survival assay with artemisinin-resistant and artemisinin-sensitive strains of P. falciparum. No differences were found in artemisinin sensitivity (P > 0.05), and there was no correlation between artemisinin activity and host hemoglobin levels. Standard antimalarial drug activity assays for representatives of the major classes of antimalarial drugs found no differences in the IC₅₀ values against P. falciparum between anemic and nonanemic RBCs. We conclude that host anemia does not influence artemisinin activity.

Research Advances on Health Effects of Edible Artemisia Species and Some Sesquiterpene Lactones Constituents

The genus Artemisia, often known collectively as "wormwood", has aroused great interest in the scientific community, pharmaceutical and food industries, generating many studies on the most varied aspects of these plants. In this review, the most recent evidence on health effects of edible Artemisia species and some of its constituents are presented and discussed, based on studies published until 2020, available in the Scopus, Web of Sciences and PubMed databases, related to food applications, nutritional and sesquiterpene lactones composition, and their therapeutic effects supported by in vivo and clinical studies. The analysis of more than 300 selected articles highlights the beneficial effect on health and the high clinical relevance of several Artemisia species besides some sesquiterpene lactones constituents and their derivatives. From an integrated perspective, as it includes therapeutic and nutritional properties, without ignoring some adverse effects described in the literature, this review shows the great potential of Artemisia plants and some of their constituents as dietary supplements, functional foods and as the source of new, more efficient, and safe medicines. Despite all the benefits demonstrated, some gaps need to be filled, mainly related to the use of raw Artemisia extracts, such as its standardization and clinical trials on adverse effects and its health care efficacy.

Nanoparticles Formulations of Artemisinin and Derivatives as Potential Therapeutics for the Treatment of Cancer, Leishmaniasis and Malaria

Cancer, malaria, and leishmaniasis remain the deadly diseases around the world although several strategies of treatment have been developed. However, most of the drugs used to treat the aforementioned diseases suffer from several pharmacological limitations such as poor pharmacokinetics, toxicity, drug resistance, poor bioavailability and water solubility. Artemisinin and its derivatives are antimalarial drugs. However, they also exhibit anticancer and antileishmanial activity. They have been evaluated as potential anticancer and antileishmanial drugs but their use is also limited by their poor water solubility and poor bioavailability. To overcome the aforementioned limitations associated with artemisinin and its derivatives used for the treatment of these diseases, they have been incorporated into nanoparticles. Several researchers incorporated this class of drugs into nanoparticles resulting in enhanced therapeutic outcomes. Their potential efficacy for the treatment of parasitic infections such as malaria and leishmaniasis and chronic diseases such as cancer has been reported. This review article will be focused on the nanoparticles formulations of artemisinin and derivatives for the treatment of cancer, malaria, and leishmaniasis and the biological outcomes (in vitro and in vivo).

Transformation of Amorphadiene Synthase and Antisilencing P19 Genes into Artemisia annua L. and its Effect on Antimalarial Artemisinin Production

Purpose: The low content of artemisinin related to the biosynthetic pathway is influenced by the role of certain enzymes in the formation of artemisinin. The regulation of genes involved in artemisinin biosynthesis through genetic engineering is a choice to enhance the content. This research aims to transform ads and p19 gene as an antisilencing into Artemisia annua and to see their effects on artemisinin production. Methods: The presence of p19 and ads genes was confirmed through polymerase chain reaction (PCR) products and sequencing analysis. The plasmids, which contain ads and/or p19 genes, were transformed into Agrobacterium tumefaciens, and then inserted into leaves and hairy roots of A. annua by vacuum and syringe infiltration methods. The successful transformation was checked through the GUS histochemical test and the PCR analysis. Artemisinin levels were measured using HPLC. Results: The percentages of the blue area on leaves by using vacuum and syringe infiltration method and on hairy roots were up to 98, 92.55%, and 99.00% respectively. The ads-p19 sample contained a higher level of artemisinin (0.18%) compared to other samples. Transformed hairy root with co-transformation of ads-p19 contained 0.095% artemisinin, where no artemisinin was found in the control hairy root. The transformation of ads and p19 genes into A. annua plant has been successfully done and could enhance the artemisinin content on the transformed leaves with ads-p19 up to 2.57 folds compared to the untransformed leaves, while for p19, cotransformed and ads were up to 2.25, 1.29, and 1.14 folds respectively. Conclusion: Antisilencing p19 gene could enhance the transformation efficiency of ads and artemisinin level in A. annua.

Antimalarial Eudesmane Sesquiterpenoids from Dobinea delavayi

Eleven new angeloylated eudesmane sesquiterpenoids, dobinins D-N (2, 3, 5, 6, 8, 9, and 11-15), and four known compounds (1, 4, 7, and 10) were isolated from the roots of Dobinea delavayi. A new oxidation product (8a) was also obtained from dobinin H (8). Their structures were elucidated by spectroscopic data and single-crystal X-ray diffraction analyses. Dobinins K-N (12-15) are the first examples of rearrangement noreudesmane analogue sesquiterpenoids with a unique 6/5-fused carbon skeleton. A putative biosynthetic pathway of compounds 12-15 is proposed. Compound 12 exhibited significant antimalarial activity superior to artemisinin with the inhibition ratio of 59.1%, and compounds 3, 5, and 15 exhibited moderate antimalarial activities against Plasmodium yoelii BY265RFP with inhibition ratios ranging from 14.5% to 18.5% at a dose of 30 mg/kg/day. In addition, the apoptosis of P. yoelii BY265RFP by the depolarization of mitochondrial membrane potential with striking ROS production, after parasitized erythrocyte lysis mediated by cytokines IL-12 and IFN-γ, may be a possible mechanism of antimalarial action of compound 12 against P. yoelii BY265RFP.

Medicinal plants used in the treatment of Malaria: A key emphasis to Artemisia, Cinchona, Cryptolepis, and Tabebuia genera

Malaria is one of the life-threatening parasitic diseases that is endemic in tropical areas. The increased prevalence of malaria due to drug resistance leads to a high incidence of mortality. Drug discovery based on natural products and secondary metabolites is considered as alternative approaches for antimalarial therapy. Herbal medicines have advantages over modern medicines, including fewer side effects, cost-effectiveness, and affordability encouraging the herbal-based drug discovery. Several naturally occurring, semisynthetic, and synthetic antimalarial medications are on the market. For example, chloroquine is a synthetic medication for antimalarial therapy derived from quinine. Moreover, artemisinin, and its derivative, artesunate with sesquiterpene lactone backbone, is an antimalarial agent originated from Artemisia annua L. A. annua traditionally has been used to detoxify blood and eliminate fever in China. Although the artemisinin-based combination therapy against malaria has shown exceptional responses, the limited medicinal options demand novel therapeutics. Furthermore, drug resistance is the cause in most cases, and new medications are proposed to overcome the resistance. In addition to conventional therapeutics, this review covers some important genera in this area, including Artemisia, Cinchona, Cryptolepis, and Tabebuia, whose antimalarial activities are finely verified.

Archangelolide: A sesquiterpene lactone with immunobiological potential from Laserpitium archangelica

Sesquiterpene lactones are secondary plant metabolites with sundry biological effects. In plants, they are synthesized, among others, for pesticidal and antimicrobial effects. Two such compounds, archangelolide and trilobolide of the guaianolide type, are structurally similar to the well-known and clinically tested lactone thapsigargin. While trilobolide has already been studied by us and others, there are only scarce reports on the biological activity of archangelolide. Here we present the preparation of its fluorescent derivative based on a dansyl moiety using azide-alkyne Huisgen cycloaddition having obtained the two sesquiterpene lactones from the seeds of Laserpitium archangelica Wulfen using supercritical CO₂ extraction. We show that dansyl-archangelolide localizes in the endoplasmic reticulum of living cells similarly to trilobolide; localization in mitochondria was also detected. This led us to a more detailed study of the anticancer potential of archangelolide. Interestingly, we found that neither archangelolide nor its dansyl conjugate did exhibit cytotoxic effects in contrast to the structurally closely related counterparts trilobolide and thapsigargin. We explain this observation by a molecular dynamics simulation, in which, in contrast to trilobolide, archangelolide did not bind into the sarco/endoplasmic reticular calcium ATPase cavity utilized by thapsigargin. Last, but not least, archangelolide exhibited anti-inflammatory activity, which makes it promising compound for medicinal purposes.

Artemisinin and its derivatives; ancient tradition inspiring the latest therapeutic approaches against malaria

Artemisinin (ART) is an endoperoxide sesquiterpene lactone, commonly used in the treatment of malaria. Although it was isolated from Artemisia annua L., a plant widely applied in Chinese Traditional Medicine, its mechanism of action remains uncertain and its clinical use is still limited due to its low solubility, its poor bioavailability and short in vivo half-life. Over time, several studies have been aimed towards the discovery of potent ART derivatives that could overcome clinical drawbacks. In this review, we focus on the multifaced aspects of ART and on the efforts spent to improve its pharmacological profile that so far culminated in the discovery of more effective drugs. Lastly, we outline the new perspectives in the ART-derivatives scenario.

AaABF3, an Abscisic Acid-Responsive Transcription Factor, Positively Regulates Artemisinin Biosynthesis in Artemisia annua

Artemisinin is well known for its irreplaceable curative effect on the devastating parasitic disease, Malaria. This sesquiterpenoid is specifically produced in Chinese traditional herbal plant Artemisia annua. Earlier studies have shown that phytohormone abscisic acid (ABA) plays an important role in increasing the artemisinin content, but how ABA regulates artemisinin biosynthesis is still poorly understood. In this study, we identified that AaABF3 encoded an ABRE (ABA-responsive elements) binding factor. qRT-PCR analysis showed that AaABF3 was induced by ABA and expressed much higher in trichomes where artemisinin is synthesized and accumulated. To further investigate the mechanism of AaABF3 regulating the artemisinin biosynthesis, we carried out dual-luciferase analysis, yeast one-hybrid assay and electrophoretic mobility shift assay. The results revealed that AaABF3 could directly bind to the promoter of ALDH1 gene, which is a key gene in artemisinin biosynthesis, and activate the expression of ALDH1. Functional analysis revealed that overexpression of AaABF3 in A. annua enhanced the production of artemisinin, while RNA interference of AaABF3 resulted in decreased artemisinin content. Taken together, our results demonstrated that AaABF3 played an important role in ABA-regulated artemisinin biosynthesis through direct regulation of artemisinin biosynthesis gene, ALDH1.

A Review of Biotechnological Artemisinin Production in Plants

Malaria is still an eminent threat to major parts of the world population mainly in sub-Saharan Africa. Researchers around the world continuously seek novel solutions to either eliminate or treat the disease. Artemisinin, isolated from the Chinese medicinal herb Artemisia annua, is the active ingredient in artemisinin-based combination therapies used to treat the disease. However, naturally artemisinin is produced in small quantities, which leads to a shortage of global supply. Due to its complex structure, it is difficult chemically synthesize. Thus to date, A. annua remains as the main commercial source of artemisinin. Current advances in genetic and metabolic engineering drives to more diverse approaches and developments on improving in planta production of artemisinin, both in A. annua and in other plants. In this review, we describe efforts in bioengineering to obtain a higher production of artemisinin in A. annua and stable heterologous in planta systems. The current progress and advancements provides hope for significantly improved production in plants.

Semisynthesis, an Anti-Inflammatory Effect of Derivatives of 1β-Hydroxy Alantolactone from Inula britannica

1β-hydroxy alantolactone, a sesquiterpene lactone mainly isolated from Inula genus plants, exhibits potent anti-inflammatory and anticancer activities. In this work, 1β-hydroxy alantolactone was isolated and five derivatives were prepared through different reactions at the C1-OH and C13-methylene motifs. The structure-activity relationships (SAR) of anti-inflammatory effects against NO production in RAW264.7 cells showed that the α-methylene-γ-butyrolactone motif was essential for NO production suppression and that retaining the C1-OH group can remarkably improve this effect. The NF-κB signaling pathway plays a pivotal role in the regulation of NO expression. Moreover, the levels of p65 and p50 phosphorylation were investigated and active compound 1 inhibited phosphorylation of p65 and p50 in TNF-α-induced NF-κB signaling. Further molecular docking suggested that 1 may target the p65 of NF-κB.

Elimination of Schistosoma mansoni in infected mice by slow release of artemisone

The current treatment of schistosomiasis is based on the anti-helminthic drug praziquantel (PZQ). PZQ affects only the adult stages of schistosomes. In addition, resistance to PZQ is emerging. We suggest a drug, which could serve as a potential alternative or complement to PZQ, and as a means of treating infections at earlier, pre-granuloma stage. Derivatives of the peroxidic antimalarial drug artemisinin have been indicated as alternatives, because both plasmodia and schistosomes are blood-feeding parasites. The mechanism of action of artemisinins is related to oxidative effects of the artemisinins on intracellular reductants leading to formation of cytotoxic reactive oxygen species. We used artemisone, which has improved pharmacokinetics and anti-plasmodial activity, and reduced toxicity compared to other artemisinins in clinical use against malaria. We infected adult mice by subcutaneous injection of S. mansoni cercariae (about 200) and treated them at various times post infection by the following methods: i. artemisone suspension administered by gavage (400-450 mg/kg); ii. subcutaneous injection of a gel containing a known concentration of artemisone (115-120 mg/kg); iii. subcutaneous insertion of the drug incorporated in a solid polymer (56-60 mg/kg); iv. intraperitoneal injection of the drug solubilized in DMSO (115-120 mg/kg). Drug administration in polymers was performed to enable slow release of the artemisone that was verified in vivo and in vitro bioassays using drug-sensitive malaria parasites. We found superior strong anti-schistosome effects up to a total reduction of worm number, mainly following repetitive treatments with the drug absorbed in the polymers (73.1% and 95.9% reduction in mice treated with artemisone in gel 7 and 14, and 21, 28 and 35 days post infection, respectively). The results indicate that artemisone has a potent anti-schistosome activity. Its main importance in this context is its effectiveness in treating hosts harboring juvenile schistosomes, before egg-deposition and induction of deleterious immune responses.

Strategies to enhance biologically active-secondary metabolites in cell cultures of Artemisia - current trends

The genus Artemisia has been utilized worldwide due to its immense potential for protection against various diseases, especially malaria. Artemisia absinthium, previously renowned for its utilization in the popular beverage absinthe, is gaining resurgence due to its extensive pharmacological activities. Like A. annua, this species exhibits strong biological activities like antimalarial, anticancer and antioxidant. Although artemisinin was found to be the major metabolite for its antimalarial effects, several flavonoids and terpenoids are considered to possess biological activities when used alone and also to synergistically boost the bioavailability of artemisinin. However, due to the limited quantities of these metabolites in wild plants, in vitro cultures were established and strategies have been adopted to enhance medicinally important secondary metabolites in these cultures. This review elaborates on the traditional medicinal uses of Artemisia species and explains current trends to establish cell cultures of A. annua and A. absinthium for enhanced production of medicinally important secondary metabolites.

Potential of marine natural products against drug-resistant fungal, viral, and parasitic infections

Antibiotics have revolutionised medicine in many aspects, and their discovery is considered a turning point in human history. However, the most serious consequence of the use of antibiotics is the concomitant development of resistance against them. The marine environment has proven to be a very rich source of diverse natural products with significant antibacterial, antifungal, antiviral, antiparasitic, antitumour, anti-inflammatory, antioxidant, and immunomodulatory activities. Many marine natural products (MNPs)-for example, neoechinulin B-have been found to be promising drug candidates to alleviate the mortality and morbidity rates caused by drug-resistant infections, and several MNP-based anti-infectives have already entered phase 1, 2, and 3 clinical trials, with six approved for usage by the US Food and Drug Administration and one by the EU. In this Review, we discuss the diversity of marine natural products that have shown in-vivo efficacy or in-vitro potential against drug-resistant infections of fungal, viral, and parasitic origin, and describe their mechanism of action. We highlight the drug-like physicochemical properties of the reported natural products that have bioactivity against drug-resistant pathogens in order to assess their drug potential. Difficulty in isolation and purification procedures, toxicity associated with the active compound, ecological impacts on natural environment, and insufficient investments by pharmaceutical companies are some of the clear reasons behind market failures and a poor pipeline of MNPs available to date. However, the diverse abundance of natural products in the marine environment could serve as a ray of light for the therapy of drug-resistant infections. Development of resistance-resistant antibiotics could be achieved via the coordinated networking of clinicians, microbiologists, natural product chemists, and pharmacologists together with pharmaceutical venture capitalist companies.

Jasmonates: signal transduction components and their roles in environmental stress responses

Jasmonates, oxylipin-type plant hormones, are implicated in diverse aspects of plant growth development and interaction with the environment. Following diverse developmental and environmental cues, jasmonate is produced, conjugated to the amino acid isoleucine and perceived by a co-receptor complex composed of the Jasmonate ZIM-domain (JAZ) repressor proteins and an E3 ubiquitin ligase complex containing the F-box CORONATINE INSENSITIVE 1 (COI1). This event triggers the degradation of the JAZ proteins and the release of numerous transcription factors, including MYC2 and its homologues, which are otherwise bound and inhibited by the JAZ repressors. Here, we will review the role of the COI1, JAZ and MYC2 proteins in the interaction of the plant with its environment, illustrating the significance of jasmonate signalling, and of the proteins involved, for responses to both biotic stresses caused by insects and numerous microbial pathogens and abiotic stresses caused by adverse climatic conditions. It has also become evident that crosstalk with other hormone signals, as well as light and clock signals, plays an important role in the control and fine-tuning of these stress responses. Finally, we will discuss how several pathogens exploit the jasmonate perception and early signalling machinery to decoy the plants defence systems.