(3,3″)-Linked Biflavanones from Ouratea spectabilis and Their Effects on the Release of Proinflammatory Cytokines in THP-1 Cells.

Ouratea spectabilis is an arborous species traditionally used in Brazil as an anti-inflammatory agent. Four new (3,3″)-linked biflavanone O-methyl ethers, named ouratein A (1), B (2), C (3), and D (4), were isolated from the bark extract of the species. Ouratein A (1) is an enantiomer of neochamagesmine A, which has never been described before. The structures were elucidated by extensive spectroscopic data analyses, whereas their absolute configurations were defined by electronic circular dichroism data. Ouratein D (4) inhibited in vitro the release of the pro-inflammatory cytokine CCL2 by lipopolysaccharide-stimulated THP-1 cells (IC50 of 3.1 ± 1.1 µM), whereas TNF and IL-1ß release were not reduced by any of the biflavanones. These findings show ouratein D (4) as a selective CCL2 inhibitor, which may have potential for the development of new anti-inflammatory agents to prevent or treat cardiovascular diseases.

Bioactive Formylated Flavonoids from Eugenia rigida: Isolation, Synthesis, and X-ray Crystallography.

Two new flavonoids, rac-6-formyl-5,7-dihydroxyflavanone (1) and 2',6'-dihydroxy-4'-methoxy-3'-methylchalcone (2), together with five known derivatives, rac-8-formyl-5,7-dihydroxyflavanone (3), 4',6'-dihydroxy-2'-methoxy-3'-methyldihydrochalcone (4), rac-7-hydroxy-5-methoxy-6-methylflavanone (5), 3'-formyl-2',4',6'-trihydroxy-5'-methyldihydrochalcone (6), and 3'-formyl-2',4',6'-trihydroxydihydrochalcone (7), were isolated from the leaves of Eugenia rigida. The individual (S)- and (R)-enantiomers of 1 and 3, together with the corresponding formylated flavones 8 (6-formyl-5,7-dihydroxyflavone) and 9 (8-formyl-5,7-dihydroxyflavone), as well as 2',4',6'-trihydroxychalcone (10), 3'-formyl-2',4',6'-trihydroxychalcone (11), and the corresponding 3'-formyl-2',4',6'-trihydroxydihydrochalcone (7) and 2',4',6'-trihydroxydihydrochalcone (12), were synthesized. The structures of the isolated and synthetic compounds were established via NMR, HRESIMS, and electronic circular dichroism data. In addition, the structures of 3, 5, and 8 were confirmed by single-crystal X-ray diffraction crystallography. The isolated and synthetic flavonoids were evaluated for their antimicrobial and cytotoxic activities against a panel of microorganisms and solid tumor cell lines.

Mansoins C-F, Oligomeric Flavonoid Glucosides Isolated from Mansoa hirsuta Fruits with Potential Anti-inflammatory Activity.

Continued investigation of the polyphenolic pool of the fruits of Mansoa hirsuta afforded four additional members of the new class of glucosylated oligomeric flavonoids comprising a flavanone core linked to 1,3-diarylpropane C6-C3-C6 units. The structures and absolute configurations of mansoins C-F (3-6) were established by analysis of NMR and electronic circular dichroism data. Mansoin C (3) was identified as a diglucosylated heterodimer, whereas mansoins D (4), E (5), and F (6) were identified as triglucosylated heterotrimers, isomeric with mansoin A (1). Mansoin F (6) inhibited TNF-α release by lipopolysaccharide-stimulated THP-1 cells (IC50 of 19.3 ± 1.3 µM) and, as with mansoin A (1), reduced the phosphorylation levels of p-65-NF-κB, when assayed at 50 µM. These results indicate that the potential anti-inflammatory properties of mansoin F (6) are probably due to inhibition of the NF-κB pathway and inhibition of TNF-α release.

Anti-TNF-α Activity of Brazilian Medicinal Plants and Compounds from Ouratea semiserrata.

Several plant species are used in Brazil to treat inflammatory diseases and associated conditions. TNF-α plays a pivotal role on inflammation, and several plant extracts have been assayed against this target, both in vitro and in vivo. The effect of 11 Brazilian medicinal plants on TNF-α release by LPS-activated THP-1 cells was evaluated. The plant materials were percolated with different solvents to afford 15 crude extracts, whose effect on TNF-α release was determined by ELISA. Among the evaluated extracts, only Jacaranda caroba (Bignoniaceae) presented strong toxicity to THP-1 cells. Considering the 14 non-toxic extracts, TNF-α release was significantly reduced by seven of them (inhibition > 80%), originating from six plants, namely Cuphea carthagenensis (Lythraceae), Echinodorus grandiflorus (Alismataceae), Mansoa hirsuta (Bignoniaceae), Ouratea semiserrata (Ochnaceae), Ouratea spectabilis and Remijia ferruginea (Rubiaceae). The ethanol extract from O. semiserrata leaves was fractionated over Sephadex LH-20 and RP-HPLC to give three compounds previously reported for the species, along with agathisflavone and epicatechin, here described for the first time in the plant. Epicatechin and lanceoloside A elicited significant inhibition of TNF-α release, indicating that they may account for the effect produced by O. semiserrata crude extract.

TNF-α inhibition elicited by mansoins A and B, heterotrimeric flavonoids isolated from Mansoa hirsuta.

Mansoins A (1) and B (2) isolated from the fruits of Mansoa hirsuta represent new glucosylated heterotrimeric flavonoids with a flavanone core linked to two 1,3-diarylpropane C6-C3-C6 units. Their structures and absolute configurations were established by analysis of their NMR and electronic circular dichroism spectroscopic data. Compounds 1 and 2 inhibited TNF-α release by LPS-stimulated THP-1 cells with different potencies, with mansoin B (2) being active at lower concentrations than mansoin A (1) (IC50 values 20.0±1.4 and 48.1±1.8 µM, respectively). These results indicate potential anti-inflammatory properties for this structural type of oligoflavonoids, especially for mansoin B (2).

Bis-spirolabdane diterpenoids from Leonotis nepetaefolia.

Ten new bis-spirolabdane diterpenoids, leonepetaefolins A-E (1, 3, 5, 7, 9) and 15-epi-leonepetaefolins A-E (2, 4, 6, 8, 10), together with eight known labdane diterpenoids (11-18) as well as two known flavonoids, apigenin and cirsiliol, were isolated from the leaves of Leonotis nepetaefolia. The structures of the new compounds were determined on the basis of 1D- and 2D-NMR experiments including (1)H, (13)C, DEPT, (1)H-(1)H COSY, HSQC, HMBC, and NOESY. The absolute configuration of an epimeric mixture of 1 and 2 was determined by X-ray crystallographic analysis. The compounds isolated were evaluated for their binding propensity in several CNS G-protein-coupled receptor assays in vitro.

Sorocenols G and H, anti-MRSA oxygen heterocyclic Diels-Alder-type adducts from Sorocea muriculata roots.

Bioassay-guided fractionation of a root extract of Sorocea muriculata led to the isolation and identification of two new oxygen heterocyclic Diels-Alder-type adducts, sorocenols G (1) and H (2), along with lupeol-3-(3' R-hydroxytetradecanoate) and oxyresveratrol. The structures of 1 and 2 were elucidated using 1D and 2D NMR spectroscopic and HRMS data and by comparison with reported values. The absolute configurations of 1 and 2 were established by analysis of their experimental and theoretically calculated CD spectra. Compounds 1 and 2 showed significant and selective activity against methicillin-resistant Staphylococcus aureus with IC50 values of 1.5 and 0.5 microM, respectively. Compound 2 also displayed antifungal activity against Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus, with IC 50 values of 5.4, 5.4, and 10.0 microM, respectively.

Capisterones A and B, which enhance fluconazole activity in Saccharomyces cerevisiae, from the marine green alga Penicillus capitatus.

A whole-cell-based assay using Saccharomyces cerevisiae strains that overexpress Candida albicans CDR1 and MDR1 efflux pumps has been employed to screen natural product extracts for reversal of fluconazole resistance. The tropical green alga Penicillus capitatus was selected for bioassay-guided isolation, leading to the identification of capisterones A and B (1 and 2), which were recently isolated from this alga and shown to possess antifungal activity against the marine pathogen Lindra thallasiae. Current work has assigned their absolute configurations using electronic circular dichroism and determined their preferred conformations in solution based on detailed NOE analysis. Compounds 1 and 2 significantly enhanced fluconazole activity in S. cerevisiae, but did not show inherent antifungal activity when tested against several opportunistic pathogens or cytotoxicity to several human cancer and noncancerous cell lines (up to 35 microM). These compounds may have a potential for combination therapy of fungal infections caused by clinically relevant azole-resistant strains.

Syncarpamide, a new antiplasmodial (+)-norepinephrine derivative from Zanthoxylum syncarpum.

A new (+)-norepinephrine derivative, syncarpamide (1), along with a known coumarin, (+)-S-marmesin (2), and one known alkaloid, decarine (3), have been isolated from the stem of Zanthoxylum syncarpum. The structure of compound 1 was elucidated on the basis of 1D and 2D NMR, MS, IR, optical rotation, and CD analyses. Its absolute stereochemistry was elucidated by synthesis of its enantiomer and subsequent comparison of CD data. Characterizations of compounds 2 and 3 were based on spectral analysis and comparison with reported data. Compounds 1 and 3 showed antiplasmodial activity, with IC(50) values of 2.04 and 1.44 microM against Plasmodium falciparum D(6) clone and 3.06 and 0.88 microM against P. falciparum W(2) clone, respectively. Compound 3 showed cytotoxicity at 56.42 microM, whereas compound 1 was not cytotoxic at 10.42 microM. Compound 1 was tested for hypotensive activity, but no activity was observed. Compound 2 showed no antiplasmodial or antimicrobial activities.

Antiparasitic alkaloids from Psychotria klugii.

Psychotria klugii yielded two new benzoquinolizidine alkaloids, klugine (1) and 7'-O-demethylisocephaeline (2), together with the previously known cephaeline (3), isocephaeline (4), and 7-O-methylipecoside (5). The structures and stereochemistry of 1 and 2 were determined by 1D and 2D NMR data and circular dichroism experiments. Cephaeline (3) demonstrated potent in vitro antileishmanial activity against Leishmania donavani (IC(50) 0.03 microg/mL) and was >20- and >5-fold more potent than pentamidine and amphotericin B, respectively, while klugine (1) (IC(50) 0.40 microg/mL) and isocephaeline (4) (IC(50) 0.45 microg/mL) were <13- and <15-fold less potent than 3. In addition, emetine (6) (IC(50) 0.03 microg/mL) was found to be as equally potent as 3, but was >12-fold more toxic than 3 against VERO cells (IC(50) 0.42 vs 5.3 microg/mL). Alkaloids 1 and 3 exhibited potent antimalarial activity against Plasmodium falciparum clones W2 and D6 (IC(50) 27.7-46.3 ng/mL). Compound 3 was cytotoxic to SK-MEL, KB, BT-549, and SK-OV-3 human cancer cells, while 1 was inactive.

Antimicrobial and antiparasitic (+)-trans-hexahydrodibenzopyrans and analogues from Machaerium multiflorum.

Machaerium multiflorum yielded two additional new (+)-trans-hexahydrodibenzopyrans (HHDBP's), machaeriol C (1) and machaeriol D (2), and three new 5,6-seco-HHDBP's, machaeridiol A (3), machaeridiol B (4), and machaeridiol C (5). Their structures and stereochemistries were determined by 1D and 2D NMR data, including HMBC, NOESY, and circular dichroism experiments. Machaeriol C (1) demonstrated in vitro antibacterial activity against Staphylococcus aureus (IC(50) 0.65 microg/mL) and methicillin-resistant S. aureus (MRSA) (IC(50) 0.70 microg/mL), while its corresponding 5,6-seco-analogues machaeridiol A (3) and machaeridiol B (4) showed antibacterial activity against S. aureus and MRSA (IC(50) 1.0-2.6 microg/mL) and antifungal activity against Candida albicans (IC(50), 2.0-3.5 microg/mL). In addition, machaeridiol B (4) demonstrated antiparasitic activities against Plasmodium falciparum D6 and W2 clones and Leishmania donavani with IC(50) values of 0.64, 0.22, and 0.9 microg/mL, respectively.