Evaluation of the antimalarial properties of Solanum incanum L. leaf extract fractions and its ability to downregulate delta aminolevulinate dehydratase to prevent the establishment of malaria infection.

ETHNOPHARMACOLOGICAL RELEVANCE: Solanum incanum L. is commonly used in traditional herbal medicine (THM) in Kenya for treating various ailments. Recent developments in disease treatment have introduced the concept of host-directed therapy (HDT). This approach involves targeting factors within the host cell that can impede the growth or replication of a pathogen. One such host factor is delta aminolevulinate dehydratase (δ-ALAD), the second enzyme in the heme biosynthesis pathway utilized by Plasmodium for growth. Studies using mice models have shown an increase in δ-ALAD expression during Plasmodium berghei infection. Another plant in the Solanum genus, S. guaranticum, has been found to inhibit δ-ALAD in red blood cells in vitro and in the brain in vivo. Is it possible that the bioactive compounds in S. incanum extracts could also be effective in HDT for malaria treatment? AIM OF STUDY: To better assess the effectiveness of S. incanum leaf extracts as a curative and prophylaxis in malaria parasite infection, and to test the plant's ability to decrease δ-ALAD expression. MATERIALS AND METHODS: The leaves of S. incanum were collected, dried, and pulverized before being subjected to a successive extraction protocol to obtain crude, hexane, ethyl acetate, and aqueous extract fractions. Phytochemical analysis was conducted on all extract fractions, followed by GC-MS analysis of the fraction with the most potent antimalarial activity. An acute toxicity study was also performed on the extracted fractions. The potency of the extract fractions as curative and prophylactic antimalarial was then evaluated in THM using Plasmodium berghei-infected mice at a dose of 100 mg/kg. The extract fraction with the highest activity was further evaluated at varying doses and its effect on δ-ALAD was measured using RT-qPCR. The percentage of parasitemia and chemosuppression, and mean survival time were used as indices of activity. RESULTS: Phytochemical analysis revealed that the ethyl acetate and aqueous extract fractions contained high terpenoids, flavonoids, and phenols levels. However, alkaloids were only present in moderate quantities in the aqueous extract, and quinones were found in high levels only in the crude extract. Additionally, all extract fractions contained saponins in high levels but lacked tannins. While the plant extracts were found to be non-toxic, they did not exhibit curative antimalarial activity. However, all extract fractions showed prophylactic antimalarial activity, with the ethyl acetate extract having the highest percentage of chemosuppression even at doses of 250 and 1000 mg/kg. In the negative control, the expression of δ-ALAD was 5.4-fold, but this was significantly reduced to 2.3-fold when mice were treated with 250 mg/kg of the ethyl acetate fraction. GC-MS analysis of the ethyl acetate fraction revealed high percentages of 2-methyloctacosane, tetracosane, and decane. CONCLUSION: The fractions extracted from S. incanum leaves have been found to possess only antimalarial prophylactic properties, with the ethyl acetate extract fraction showing the most effective results. The activity of this fraction may be attributed to its ability to decrease the expression of δ-ALAD, as it contains an alkane compound implicated with enzyme-inhibitory activity.

Cohesin-mediated NF-κB signaling limits hematopoietic stem cell self-renewal in aging and inflammation.

Organism aging is characterized by increased inflammation and decreased stem cell function, yet the relationship between these factors remains incompletely understood. This study shows that aged hematopoietic stem and progenitor cells (HSPCs) exhibit increased ground-stage NF-κB activity, which enhances their responsiveness to undergo differentiation and loss of self-renewal in response to inflammation. The study identifies Rad21/cohesin as a critical mediator of NF-κB signaling, which increases chromatin accessibility in the vicinity of NF-κB target genes in response to inflammation. Rad21 is required for normal differentiation, but limits self-renewal of hematopoietic stem cells (HSCs) during aging and inflammation in an NF-κB-dependent manner. HSCs from aged mice fail to down-regulate Rad21/cohesin and inflammation/differentiation signals in the resolution phase of inflammation. Inhibition of cohesin/NF-κB reverts hypersensitivity of aged HSPCs to inflammation-induced differentiation and myeloid-biased HSCs with disrupted/reduced expression of Rad21/cohesin are increasingly selected during aging. Together, Rad21/cohesin-mediated NF-κB signaling limits HSPC function during aging and selects for cohesin-deficient HSCs with myeloid-skewed differentiation.

Methanolic extract of Agerantum conyzoides exhibited toxicity and growth disruption activities against Anopheles gambiae sensu stricto and Anopheles arabiensis larvae.

BACKGROUND: Vector control remains the mainstay to effective malaria management. The negative implications following persistent application of synthetic insecticides geared towards regulation of mosquito populations have necessitated prospection for ecofriendly effective chemistries. Plant-derived compounds have the potential to control malaria-transmitting mosquito populations. Previously, Agerantum conyzoides extracts have demonstrated toxicity effects on disease-transmitting mosquitoes. However, their efficacy in controlling Afrotropical malaria vectors remains unclear. Herein, the toxicity and growth disruption activities of crude methanolic leaf extract of A. conyzoides on Anopheles gambiae sensu stricto and An. arabiensis larvae were assessed. METHODS: Late third (L3) instars of An. gambiae s.s and An. arabiensis larvae were challenged with increasing doses of crude methanolic extract of A. conyzoides. The larval mortality rates were recorded every 24 h and the LC50 values determined at their associated 95% confidence levels. ANOVA followed by Post-hoc Student-Newman-Keuls (SNK) test was used to compare results between treatment and control groups. Phytochemical profiling of the extract was performed using standard chemical procedures. RESULTS: Treatment of larvae with the methanolic extract depicted dose-dependent effects with highest mortality percentages of ≥ 69% observed when exposed with 250 ppm and 500 ppm for 48 h while growth disruption effects were induced by sublethal doses of between 50-100 ppm for both species. Relative to experimental controls, the extract significantly reduced larval survival in both mosquito species (ANOVA, F(8,126) = 43.16776, P < 0.001). The LC50 values of the extract against An. gambiae s.s ranged between 84.71-232.70 ppm (95% CI 81.17-239.20), while against An. arabiensis the values ranged between 133.46-406.35 ppm (95% CI 131.51-411.25). The development of the juvenile stages was arrested at pupal-larval intermediates and adult emergence. The presence of alkaloids, aglycone flavonoids, triterpenoids, tannins and coumarins can partly be associated with the observed effects. CONCLUSION: The extract displayed considerable larvicidal activity and inhibited emergence of adult mosquitoes relative to experimental controls, a phenomenon probably associated with induced developmental hormone imbalance. Optimization of the bioactive compounds could open pathways into vector control programmes for improved mosquito control and reduced malaria transmission rates.

Antimicrobial and cytotoxicity properties of the organic solvent fractions of Clerodendrum myricoides (Hochst.) R. Br. ex Vatke: Kenyan traditional medicinal plant.

BACKGROUND/AIM: Clerodendrum myricoides is a Kenyan herbal plant used in the management of respiratory diseases. In the current study, we investigated in vitro antimicrobial activity, cytotoxicity, and phytochemical screening of C. myricoides. MATERIALS AND METHODS: Antimicrobial activities of C. myricoides organic fractions against array of microorganisms including: (i) Mycobacterium tuberculosis (MTB) H37Rv, (ii) Staphylococcus aureus, (iii) Klebsiella pneumoniae, (iv) Escherichia coli, (v) Candida albicans, (vi) Pseudomonas aeruginosa, (vii) Cryptococcus neoformans, (viii) Salmonella typhi, (ix) Shigella sonnei, and (x) Methicillin-resistant S. aureus (MRSA) were investigated by disc diffusion and microdilution techniques. Antituberculous activity was investigated using BACTEC MGIT 960 system while cytotoxicity was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay on HEp-2 cells. Finally, phytochemicals were screened using standard procedures. RESULTS: Methanolic fractions exhibited a broad spectrum activity inhibiting 75% of test pathogens. It had the highest activity with minimal inhibition concentration (MIC) values of ≤62.5 µg/ml recorded against 62.5% tested microbes. It yielded the highest zone of inhibition of 20.3 mm (S. aureus), lowest MIC of <12.5 µg/ml (MTB), and the lowest minimal bactericidal concentration of 62.5 µg/ml (C. albicans), within the acceptable toxicity limit (CC50 >90 µg/ml). The phytochemicals largely believed to be responsible for the observed activity included: Alkaloid, phenols, anthraquinones, terpenoids, and flavonoids. CONCLUSION: Methanolic fraction had remarkable activity against MRSA, S. aureus, E. coli, S. sonnei, C. albicans, and MTB, which are of public health concerns due to drug resistance and as sources of community and nosocomial infections. To the best of our knowledge, this is the first report exploring the antituberculous activity of C. myricoides and thence a major output in search of novel, safe drug leads to mitigate the global tuberculosis threat.

Antimicrobial and cytotoxicity properties of the crude extracts and fractions of Premna resinosa (Hochst.) Schauer (Compositae): Kenyan traditional medicinal plant.

BACKGROUND: Premna resinosa (Hochst.) Schauer also called "mukarakara" in Mbeere community of Kenya is used in the management of respiratory illness. In this study we investigated antituberculous, antifungal, antibacterial activities including cytotoxicity and phytochemical constituents of this plant. METHODS: Antibacterial and antifungal activities were investigated by disc diffusion and micro dilution techniques. Antituberculous activity was investigated using BACTEC MGIT 960 system while cytotoxicity was analyzed by MTT assay on Vero cells (Methanolic crude extract) and HEp-2 cells (fractions). Finally, phytochemicals were profiled using standard procedures. RESULTS: P. resinosa had high antituberculous activity with a MIC of <6.25 µg/ml in ethyl acetate fraction. The antibacterial activity was high and broad spectrum, inhibiting both Gram positive and Gram negative bacteria. Dichloromethane fraction had the best antibacterial MIC of 31.25 µg/ml against Methicillin-resistant S. aureus while Ethyl acetate fraction had the highest zone of inhibition of 22.3±0.3 against S. aureus. Its effects on tested fungi were moderate with petro ether fraction giving an inhibition of 10.3±0.3 on C. albicans. The crude extract and two fractions (petro ether and methanol) were not within the acceptable toxicity limits, however dichloromethane and ethyl acetate fractions that exhibited higher activity were within the acceptable toxicity limit (CC50<90). The activity can to some extent be associated to alkaloids, flavonoids, terpenoids, anthraquinones and phenols detected in this plant extracts. CONCLUSION: Our findings demonstrate that P. resinosa has high selective potential as a source of novel lead for antituberculous, antibacterial and antifungal drugs. Of particular relevance is high activity against MRSA, S. aureus, C. albicans and MTB which are great public health challenge due to drug resistance development and as major sources of community and hospital based infections.