Isoprenoid precursor biosynthesis is the essential metabolic role of the apicoplast during gametocytogenesis in Plasmodium falciparum.

The malaria parasite harbors a relict plastid called the apicoplast and its discovery opened a new avenue for drug discovery and development due to its unusual, nonmammalian metabolism. The apicoplast is essential during the asexual intraerythrocytic and hepatic stages of the parasite, and there is strong evidence supporting its essential metabolic role during the mosquito stages of the parasite. Supply of the isoprenoid building blocks isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) is the essential metabolic function of the apicoplast during the asexual intraerythrocytic stages. However, the metabolic role of the apicoplast during gametocyte development, the malaria stages transmitted to the mosquito, remains unknown. In this study, we showed that production of IPP for isoprenoid biosynthesis is the essential metabolic function of the apicoplast during gametocytogenesis, by obtaining normal gametocytes lacking the apicoplast when supplemented with IPP. When IPP supplementation was removed early in gametocytogenesis, developmental defects were observed, supporting the essential role of isoprenoids for normal gametocytogenesis. Furthermore, mosquitoes infected with gametocytes lacking the apicoplast developed fewer and smaller oocysts that failed to produce sporozoites. This finding further supports the essential role of the apicoplast in establishing a successful infection in the mosquito vector. Our study supports isoprenoid biosynthesis as a valid drug target for development of malaria transmission-blocking inhibitors.

Antimalarial 5,6-Dihydro-α-pyrones from Cryptocarya rigidifolia: Related Bicyclic Tetrahydro-α-Pyrones Are Artifacts1.

Antimalarial bioassay-guided fractionation of an EtOH extract of the root wood of Cryptocarya rigidifolia (Lauraceae) led to the isolation of the five new 5,6-dihydro-α-pyrones cryptorigidifoliols A-E (1-5) and the six bicyclic tetrahydro-α-pyrone derivatives cryptorigidifoliols F-K (6-11). The structure elucidations of all compounds were made on the basis of the interpretation of spectroscopic data and chemical derivatization, and the relative and absolute configurations were determined by NOESY, electronic circular dichroism (ECD), and (1)H NMR analysis of α-methoxyphenylacetyl (MPA) derivatives. The bicyclic tetrahydro-α-pyrone derivatives were identified as products of acid-catalyzed intramolecular Michael addition of the 5,6-dihydro-α-pyrones in the presence of silica gel. A structure-activity relationship study suggested that the presence of an α,ß-unsaturated carbonyl moiety is not essential for potent antimalarial activity.

Neolignans and other metabolites from Ocotea cymosa from the Madagascar rain forest and their biological activities.

Ten new neolignans including the 6'-oxo-8.1'-lignans cymosalignans A (1a), B (2), and C (3), an 8.O.6'-neolignan (4a), ococymosin (5a), didymochlaenone C (6a), and the bicyclo[3.2.1]octanoids 7-10 were isolated along with the known compounds 3,4,5,3',5'-pentamethoxy-1'-allyl-8.O.4'-neolignan, 3,4,5,3'-tetramethoxy-1'-allyl-8.O.4'-neolignan, didymochlaenone B, virologin B, ocobullenone, and the unusual 2'-oxo-8.1'-lignan sibyllenone from the stems or bark of the Madagascan plant Ocotea cymosa. The new 8.O.6'-neolignan 4a, dihydrobenzofuranoid 5a, and the bicyclo[3.2.1]octanoid 7a had in vitro activity against Aedes aegypti, while the new compounds 5a, 7a, 8, and 10a and the known virolongin B (4b) and ocobullenone (10b) had antiplasmodial activity. We report herein the structure elucidation of the new compounds on the basis of spectroscopic evidence, including 1D and 2D NMR spectra, electronic circular dichroism, and mass spectrometry, and the biological activities of the new and known compounds.

Antiproliferative Compounds from Cleistanthus boivinianus from the Madagascar Dry Forest.

The two new lignans 3α-O-(ß-D-glucopyranosyl)desoxypodophyllotoxin (1) and 4-O-(ß-D-glucopyranosyl)dehydropodophyllotoxin (2) were isolated from Cleistanthus boivinianus, together with the known lignans deoxypicropodophyllotoxin (3), (±)-ß-apopicropodophyllin (4), (-)-desoxypodophyllotoxin (5), (-)-yatein (6), and ß-peltatin-5-O-ß-D-glucopyranoside (7). The structures of all compounds were characterized by spectroscopic techniques. Compounds 1, 4, and 5 showed potent antiproliferative activities against the A2780 ovarian cancer cell line, with IC50 values of 33.0 ± 3.6, 63.1 ± 6.7, and 230 ± 1 nM, respectively. Compounds 2 and 7 showed only modest A2780 activities, with IC50 values of 2.1 ± 0.3 and 4.9 ± 0.1 µM, respectively, while compounds 3 and 6 had IC50 values of >10 µM. Compound 1 also had potent antiproliferative activity against the HCT-116 human colon carcinoma cell line, with an IC50 value of 20.5 nM, and compound 4 exhibited modest antiproliferative activity against the A2058 human caucasian metastatic melanoma and MES-SA human uterine sarcoma cell lines, with IC50 values of 4.6 and 4.0 µM, respectively.

Eubacterium callanderi bacteremia: A case report.

Eubacterium species are a group of obligated anaerobic gram-positive bacilli that are recognized as commensals of the gastrointestinal tract flora. Cases of bacteremia mediated by Eubacterium are rare. This report describes a case of bacteremia caused by Eubacterium callanderi in an 82-year-old female with a history of a cecal perforation secondary to an obstructing sigmoid stricture. The results showed the utility of using whole genome sequencing to identify the causative agent and underlined the significance to identify anaerobic organisms in diagnostic microbiology practice and to perform antimicrobial susceptibility testing to guide therapy and enhance patient outcomes.

A steroid receptor coactivator acts as the DNA-binding partner of the methoprene-tolerant protein in regulating juvenile hormone response genes.

Methoprene-tolerant (Met) protein is a juvenile hormone (JH) receptor in insects. JH-bound Met forms a complex with the ßFtz-F1-interacting steroid receptor coactivator (FISC) and together they regulate JH response genes in mosquitoes. Both proteins contain basic helix-loop-helix (bHLH) and PAS motifs. Here we demonstrated that FISC is the obligatory partner of Met for binding to JH-response elements (JHREs). Met or FISC alone could not bind a previously characterized JHRE, while formation of the Met-FISC complex was necessary and sufficient to bind to the JHRE. This binding required participation of the DNA-binding domains of both Met and FISC. The optimal DNA sequence recognized by Met and FISC contained a core consensus sequence GCACGTG. While formation of the Met-FISC complex in mosquito cells was induced by JH, heterodimerization and DNA binding of bacterially expressed Met and FISC were JH-independent, implying that additional mosquito proteins were required to modulate formation of the receptor complex.

Antiproliferative and antimalarial sesquiterpene lactones from Piptocoma antillana from Puerto Rico.

Bioassay-directed fractionation of an antiproliferative ethanol extract of the leaves and twigs of Piptocoma antillana (Asteraceae) afforded two new goyazensolide-type sesquiterpene lactones named 5-O-methyl-5-epiisogoyazensolide (1) and 15-O-methylgoyazensolide (2), together with the known compounds 1-oxo-3,10-epoxy-8-(2-methylacr1 0-epoxy-8-(2-methylacryloxy)-l 5-acetoxygermacra-2,4, 11(1 3)-trien-6(12)-olide (3) and 5-epiisogoyazensolide (4). The structure elucidation of all compounds was carried out based on NMR and mass spectroscopic data analyses. The relative and absolute configurations of all the isolated compounds were determined from their CD and NOESY NMR spectra. Compounds 1-4 showed moderately potent antiproliferative activities against A2780 ovarian cancer cells, with IC50 values of 1.5 +0.5, 0.6 ± 0.3, 1.62 ± 0.05, and 1.56 ± 0.04 µM, respectively. They also displayed antimalarial activity against Plasmodiumfalciparum, with IC50 values of 6.2 05 22 ± 0.5, 2.2± 0.5, 8.0 ± 0.4, and 9.0 ± 0.6 µM, respectively.