Antiprotozoal and cytotoxic naphthalene derivatives from Diospyros assimilis

A potential DES catalyst for the fast and green synthesis of benzochromenopyrimidines and pyranopyrimidines

A gentisic acid based-Deep Eutectic Solvent (MTPPBr/GA-DES) was synthesized by mixing one mole of methyl triphenylphosphonium bromide (MTPPBr) and one mole of gentisic acid (GA: 2,5-dihydroxy-benzoic acid) based on the eutectic point phase diagram. Then, it was characterized by FT-IR, NMR, densitometer, and TGA/DTA techniques and used as a potent and novel catalyst for the fast and green synthesis of: (i) Five new 2(a-e) and five known 2(f-j) benzo[6,7]chromeno[2,3-d]pyrimidines and (ii) One new (3a) and eleven known 3(b-l) pyrano[2,3-d]pyrimidines, in solvent-free conditions, short reaction times, and high yields. It is important to mention that for the synthesis of 2(a-j), there is only one reference which states that the reaction times are extremely long (720-2400 min), while these times are reduced to approximately 35-50 min in our proposed strategy, indicatinging that the rate of reactions will be 20-48 times faster, which is the clear and most obvious advantage of our approach.

A new DES-mediated synthesis of Henna-based benzopyranophenazines and benzoxanthenetriones

MTPPBr/THFTCA-DES was prepared as a new deep eutectic solvent (DES) from a mixture (molar ratio 7:3) of methyltriphenyl-phosphonium bromide (MTPPBr) and tetrahydrofuran-2,3,4,5-tetra-carboxylic acid (THFTCA), and characterized with various spectroscopic techniques, densitometer, and eutectic point. Then, it was used as a new and powerful catalyst for the synthesis of two sets of biologically important compounds, namely the Henna-based benzopyranophenazines and benzoxan-thenetriones. Solvent-free conditions, short reaction time, high efficiency, and easy recycling and separation of the DES catalyst are among the most important features of the presented method. Also, there is a nice consistency between the proposed structure of the DES compound, the integration values of the 1H NMR peaks, and the ratio of MTPPBr to THFTCA obtained from the eutectic point phase diagram. In addition, the reduction of peak splitting patterns in DES compared to the two primary materials can be good evidence of the formation of hydrogen bonds between the two components.

The malaria blood stage antigen PfCyRPA formulated with the TLR-4 agonist adjuvant GLA-SE elicits parasite growth inhibitory antibodies in experimental animals

BACKGROUND

Plasmodium falciparum cysteine-rich protective antigen (PfCyRPA) is an invasion complex protein essential for erythrocyte invasion. In contrast to several previously clinically tested merozoite vaccine candidate antigens, PfCyRPA is not polymorphic, making it a promising candidate antigen for blood stage vaccine development.

METHODS

Mice and rabbits were immunized with vaccine formulations of recombinantly expressed PfCyRPA adjuvanted either with the glucopyranosyl lipid A (GLA) containing adjuvants GLA-LSQ, GLA-SE, GLA-Alum or with Nanoalum. ELISA and indirect immunofluorescence assays (IFA) were used to analyse elicited IgG titers and the P. falciparum growth inhibitory activity was determined with a standardized in vitro [³H]-hypoxanthine incorporation assay.

RESULTS

In the mouse experiments, the GLA adjuvanted formulations were superior to the Nanoalum formulation with respect to antibody titer development, IFA sero-conversion rates and in vitro parasite growth-inhibitory activity. In rabbits, the highest titers of parasite growth inhibitory antibodies were obtained with the GLA-SE formulation. Comparable mean ELISA IgG endpoint titers were reached in rabbits after three immunizations with GLA-SE adjuvanted PfCyRPA doses of 5, 25 and 100 µg, but with 100 µg of antigen, only two immunizations were required to reach this titer.

CONCLUSION

PfCyRPA formulated with the human-compatible adjuvant GLA-SE represents an attractive vaccine candidate for early clinical testing in a controlled P. falciparum blood stage challenge trial.

Micromorphology and Histology of the Secretory Apparatus of Diospyros villosa (L.) de Winter Leaves and Stem Bark

Diospyros villosa is a perennial species prominently acknowledged for its local medicinal applications. The native utilisation of this species in traditional medicine may be ascribed to the presence of secretory structures and their exudate (comprised of phytochemicals). However, the morphological nature and optical features of the secretory structures in D. villosa remain largely unclear. This study was directed to ascertain the occurrence and adaptive features of structures found within the leaves and stem bark of D. villosa using light and electron microscopy techniques. The current study notes the existence of trichomes, and other secretory structures were noted. SEM indicated the presence of non-glandular hirsute trichomes with bulky stalk on both leaves and stem surfaces. Transverse stem sections revealed the existence of crystal idioblasts. Moreover, the presence of the main phytochemical groups and their localisation within the foliage and stem bark was elucidated through various histochemical tests. The trichomal length and density were also assessed in leaves at different stages of development. The results indicated that the trichomal density at different stages of development of the D. villosa leaves and stem bark was not significantly different from one another, F_(3,39) = 1.183, p = 0.3297. The average length of the non-glandular trichomes in the emergent, young and mature leaves, as well as in the stem, was recorded to be 230 ± 30.6 µm, 246 ± 40.32 μm, 193 ± 27.55 µm and 164 ± 18.62 µm, respectively. The perimeter and circumference of the observed trichomes in the developmental stages of D. villosa leaf and the stem bark were not statistically different, F_(3,39) = 1.092, p = 0.3615. The results of histochemical tests showed the existence of phenols alkaloids, which are medicinally important and beneficial for treatment of diseases. The findings of this study, being reported for the first time may be considered in establishing microscopic and pharmacognostic measure for future identification and verification of natural herbal plant. Trichomal micromorphology and histological evaluations could be utilised as a tool for appropriate description for the assessment of this species.

Sedative-hypnotic effect and in silico study of dinaphthodiospyrols isolated from Diospyros lotus Linn

Traditionally, Diospyros lotus Linn is used for insomnia and other associated disorders. Insomnia is a worldwide disorder with different etiology which is treated with different synthetic medicine associated with addiction. Natural products are generally devoid of such addition with good efficacy. Current research was conducted to evaluate the sedative and hypnotic effects of dimeric naphthoquinones such as dinaphthodiospyrol A (1), dinaphthodiospyrol B (2), dinaphthodiospyrol C (3), dinaphthodiospyrol D (4), dinaphthodiospyrol E (5) and dinaphthodiospyrol F (6) isolated from the chloroform fractions of D. lotus. The sedative and hypnotic effects at the dose of 5 and 10 mg/kg (each compound) were assessed through open field and phenobarbital induced sleep test, respectively. In the case of open field test the administration of tested compounds significantly hindered the movement of animals, while in case of hypnotic effect the tested samples significantly improved the onset and duration of sleep as compared to control. The overall effects were in a dose dependent manner. The compounds were also assessed for acute toxicity, but no toxicity was observed. In this regard, our research triumphantly announced the strong chemical base for the folkloric values of the plant with their fringe benefits and implemented a platform for further aspects of mechanistic and clinical studies. A possible mechanism of in vivo inhibition was studied by using docking simulations on GABA receptors. Binding orientations and types of interactions revealed that a possible mechanism behind these pharmacological actions might be interaction with GABA receptors.

Antibacterial, Antifungal, Antioxidant, and Docking Studies of Potential Dinaphthodiospyrols from Diospyros lotus Linn Roots

The main aims of this investigation were the isolation of dimeric naphthoquinones, a new class of dinaphthodiospyrols (1-7), from chloroform fractions and screening them for antibacterial, antifungal, and antioxidant potential. The susceptibility of the isolated compounds, namely, dinaphthodiospyrol A (1), dinaphthodiospyrol B (2), dinaphthodiospyrol C (3), dinaphthodiospyrol D (4), dinaphthodiospyrol E (5), dinaphthodiospyrol F (6), and dinaphthodiospyrol G (7) was assessed for antibacterial potential using well diffusion methods. The isolated compounds showed excellent antibacterial activity against selected bacterial strains, including Gram-positive Bacillus subtilis, Streptococcus epidermis, and Bacillus subtilis, and Gram-negative bacteria Klebsiella pneumonia with the zones of inhibition 6 to 26 nm. The standard drug Imipenem showed a maximum inhibitory zone 30 to 35 nm. Similarly, the isolated compounds were screened for antifungal properties, which showed an excellent reduction in the growth of selected fungal strain including Candida albicans, Aspergillus flavus, Fusarium solani, Trichyton logifusus, Microsporum canis , and Candida glabrata. Among all the screened compounds, 7 exhibited good activity (30-49 mm), followed by compounds 5 and 6, (35-46 mm), while compounds 1-4 showed a moderate effect (8-28 mm) against the selected fungal strain against miconazole which showed potent effects (101-110.98 mm). The isolated compounds were also screened for 1, 1-diphenyl-2-picrylhydrazyl (DPPH) activity. In vitro-based free radical was employed using ascorbic acid as a standard antioxidant. The tested compounds (1-7) exhibited significant antioxidant activity in a concentration-dependent manner. The dinaphthodiospyrol 7 exhibited 97.32% scavenging activity, followed by dinaphthodiospyrol 6, 92.01%, and compounds 5 and 4 with 89.90 and 88.43% scavenging activity at 100 μg/mL, respectively; ascorbic acid showed 96.45% scavenging effect. Furthermore, docking analysis was performed to know the exact binding mode of the tetra-substituted derivatives of dinaphthodiospyrols to the selected target proteins. From the docking analysis, it was found that the docking results are well correlated with the experimental observations. In conclusion, the dinaphthodiospyrols exhibited excellent antibacterial, antifungal, and free radical scavenging potential.

Bioactive Compounds from Medicinal Plants in Myanmar

Myanmar is a country with rich natural resources and of these, medicinal plants play a vital role in the primary health care of its population. The people of Myanmar have used their own system of traditional medicine inclusive of the use of medicinal plants for 2000 years. However, systematic and scientific studies have only recently begun to be reported. Researchers from Japan, Germany, and Korea have collaborated with researchers in Myanmar on medicinal plants since 2000. During the past two decades, over 50 publications have been published in peer-reviewed journals. Altogether, 433 phytoconstituents, including 147 new and 286 known compounds from 26 plant species consisting of 29 samples native to Myanmar, have been collated. In this contribution, phytochemical and biological investigations of these plants, including information on traditional knowledge are compiled and discussed.

4-Benzyloxylonchocarpin and Muracatanes A-C from Ranunculus muricatus L. and Their Biological Effects

Ranunculus muricatus L. is a spiny fruit buttercup that is used in various traditional medicinal systems. In the current investigation of R. muricatus, the new chalcone 4-benzyloxylonchocarpin (1), the new anthraquinone muracatanes A (2), the new-to-nature anthraquinone muracatanes B (3), and the new naphthalene analog muracatanes C (4) were isolated, in addition to the three previously reported compounds, 4-methoxylonchocarpin (5), β-sitosterol (6), and β-sitosterol β-D-glucopyranoside (7). Their structures were elucidated using 1D (¹H and ¹³C) and 2D (COSY, HSQC, and HMBC) NMR spectroscopy and HR-ESI-MS. Chalcone 1 showed potent acetylcholinesterase inhibitory effects with K_i of 5.39 µM and K_i′ of 3.54 µM, but none of the isolated compounds showed inhibitory activity towards butyrylcholinesterase. Anthraquinone 3 illustrated α-glucosidase inhibitory effects with IC₅₀-values of 164.46 ± 83.04 µM. Compound 5 displayed moderate cytotoxic activity towards ovarian carcinoma (A2780, IC₅₀ = 25.4 µM), colorectal adenocarcinoma (HT29, IC₅₀ = 20.2 µM), breast cancer (MCF7, IC₅₀ = 23.7 µM), and thyroid carcinoma (SW1736, IC₅₀ = 26.2 µM) while it was inactive towards pharynx carcinoma (FaDu: IC₅₀ > 30 µM).

Cichorins D-F: Three New Compounds from Cichorium intybus and Their Biological Effects

Cichorium intybus L., (chicory) is employed in various traditional medicines to treat a wide range of diseases and disorders. In the current investigation, two new naphthalane derivatives viz., cichorins D (1) and E (2), along with one new anthraquinone cichorin F (3), were isolated from Cichorium intybus. In addition, three previously reported compounds viz., β-sitosterol (4), β-sitosterol β-glucopyranoside (5), and stigmasterol (6) were also isolated from Cichorium intybus. Their structures were established via extensive spectroscopic data, including 1D (1H and 13C) and 2D NMR (COSY, HSQC and HMBC), and ESIMS. Cichorin E (2) has a weak cytotoxic effect on breast cancer cells (MDA-MB-468: IC50: 85.9 µM) and Ewing's sarcoma cells (SK-N-MC: IC50: 71.1 µM); cichorin F (3) also illustrated weak cytotoxic effects on breast cancer cells (MDA-MB-468: IC50: 41.0 µM and MDA-MB-231: IC50: 45.6 µM), and SK-N-MC cells (IC50: 71.9 µM). Moreover compounds 1-3 did not show any promising anthelmintic effects.

In vivo analgesic, anti-inflammatory, and sedative activity and a molecular docking study of dinaphthodiospyrol G isolated from Diospyros lotus

BACKGROUND

Analgesic, anti-inflammatory, and sedative drugs are available with potential side effects such as peptic ulcer and addiction among other things. In this regard, research is underway to find safe, effective, and economical drugs free of these side effects. In this study, an isolated natural product from Diospyros lotus, was tested for the aforementioned bioactivities.

OBJECTIVES

To evaluate analgesic, anti-inflammatory, and sedative potential of D. lotus extracts in animal paradigms using BALB/c mice as experimental model.

METHODS

Analgesic, anti-inflammatory and sedative activities of dinaphthodiospyrol G (1) isolated from the chloroform fraction of D. lotus were evaluated using different experimental procedures. Anti-inflammatory effect was evaluated using the carrageenan and histamine-induced paw edema, whereas the antinociceptive effect was quantified by means of the hot plate analgesiometer. On the other hand, the sedative effect was determined using animal assay for screening the locomotors effects of compound 1. Compound 1 was also subjected to molecular modeling studies against cyclooxygenase enzymes.

RESULTS

Results from this investigation showed that the extract is devoid of anti-inflammatory and antinociceptive potentials but has a significant sedative effect, whereas the tested compound exhibited 55.23 and 78.34% attenuation in paw edema by carrageenan and histamine assays, respectively. A significant (p < 0.001) and dose-dependent antinociceptive and sedative effects were demonstrated by the isolated compound. Molecular docking and dynamics simulation studies of the isolated compound against cyclooxygenase enzyme indicated that compound 1 forms specific interactions with key residues in the active site of the target receptor, which validates the potential use of the isolated compound as cyclooxygenase inhibitor.

CONCLUSIONS

Compound 1 exhibited remarkable analgesic, anti-inflammatory, and sedative activities. These findings strongly justify the traditional use of D. lotus in the treatment of inflammation, pain, and insomnia.

Anti-inflammatory, Antibacterial, Toxicological Profile, and In Silico Studies of Dimeric Naphthoquinones from Diospyros lotus

Diospyros lotus, also known as date-plum, belongs to the Ebenaceae family and is mostly recognized as a rootstock for D. kaki. Similar classes of naphthoquinones in D. lotus are investigated against cancer and inflammation and have antimicrobial, sedative, and analgesic properties. Six chemical constituents (1-6) were isolated from Diospyros lotus and tested for anti-inflammatory effects at the dose of 2.5 and 5 mg/kg, i.p., using carrageenan (1%, 0.05 ml)-induced paw edema. The maximum protection against carrageenan-induced edema was observed for compounds 1 and 2. Both studied compounds demonstrated significant anti-inflammatory effect after the 3rd hour of posttreatment. The maximum anti-inflammatory effect of compound 1 was 85.96%, while that of compound 2 was 81.44%, followed by compounds 5 and 6, which exhibited 80.11% and 82.45% effect, respectively. Similarly, histamine-induced inflammation was significantly antagonized by 1, 2, 5, and 6 with 87.99%, 82.18±1.8, 80.40±1.59, and 77.44% effects, respectively, at 5 mg/kg after the 2nd hour of posttreatment. The rest of the tested compounds did not show any significant effect as compared to the negative control. Interestingly, no toxicity was observed at higher doses. Moreover, the extracted compounds showed remarkable antibacterial activity against the Gram-positive bacteria and no effect against the Gram-negative bacteria. Docking studies on target cyclooxygenases showed that all the compounds established interactions with the key amino acid residues present in the additional pocket of COX-2. Hence, these compounds may act as selective COX-2 inhibitors. In conclusion, the findings of the current study suggest that the roots of Diospyros lotus may contain some anti-inflammatory and antibacterial agents with minimal toxicological effects and accordingly this plant product is recommended for further investigations.

Vaccination with virosomally formulated recombinant CyRPA elicits protective antibodies against Plasmodium falciparum parasites in preclinical in vitro and in vivo models

The Plasmodium falciparum (Pf) cysteine-rich protective antigen (PfCyRPA) has emerged as a promising blood-stage candidate antigen for inclusion into a broadly cross-reactive malaria vaccine. This highly conserved protein among various geographical strains plays a key role in the red blood cell invasion process by P. falciparum merozoites, and antibodies against PfCyRPA can efficiently prevent the entry of the malaria parasites into red blood cells. The aim of the present study was to develop a human-compatible formulation of the PfCyRPA vaccine candidate and confirming its activity in preclinical studies. Recombinant PfCyRPA expressed in HEK 293 cells was chemically coupled to phosphoethanolamine and then incorporated into the membrane of unadjuvanted influenza virosomes approved as antigen delivery system for humans. Laboratory animals were immunised with the virosome-based PfCyRPA vaccine to determine its immunogenic properties and in particular, its capacity to elicit parasite binding and growth-inhibitory antibodies. The vaccine elicited in mice and rabbits high titers of PfCyRPA-specific antibodies that bound to the blood-stage parasites. At a concentration of 10 mg/mL, purified total serum IgG from immunised rabbits inhibited parasite growth in vitro by about 80%. Furthermore, in a P. falciparum infection mouse model, passive transfer of 10 mg of purified total IgG from PfCyRPA vaccinated rabbits reduced the in vivo parasite load by 77%. Influenza virosomes thus represent a suitable antigen delivery system for the induction of protective antibodies against the recombinant PfCyRPA, designating it as a highly suitable component for inclusion into a multivalent and multi-stage virosomal malaria vaccine.

Synthesis, Antimicrobial Properties, and Inhibition of Catalase Activity of 1,4-Naphtho- and Benzoquinone Derivatives Containing N-, S-, O-Substituted

A series of new 1,4-naphtho- and benzoquinone derivatives possessing N-, S-, O-substituted groups which has not been reported yet has been synthesized from 2,3-dichloro-1,4-naphthoquinone 1 and 2,3,5,6-tetrachlorocyclohexa-2,5-diene-1,4-dione 15 involving a Michael addition. In the synthesized compounds, antimicrobial activity at low concentrations against Escherichia coli B-906, Staphylococcus aureus 209-P, and Mycobacterium luteum B-917 bacteria and Candida tenuis VKM Y-70 and Aspergillus niger F-1119 fungi in comparison with controls was identified. 2-Chloro-3-((2-(piperidin-1-yl)ethyl)amino)naphthalene-1,4-dione 3g and 2,5-dichloro-3-ethoxy-6-((2,4,6-trifluorophenyl)amino)cyclohexa-2,5-diene-1,4-dione 17 were the most potent, with a minimum inhibitory concentration value of 15.6 μg/mL against test-culture M. luteum and S. aureus, respectively. Furthermore, in this work, a catalase activity of benzo- and naphthoquinone derivatives was examined for the first time. The catalase activity of benzo- and naphthoquinone derivatives was determined, showing that compound 3g had significant inhibition activity for catalase enzyme.

Bioassay-guided isolation of novel and selective urease inhibitors from Diospyros lotus

Two new dimeric naphthoquinones, 5',8'-dihydroxy-6,6'-dimethyl-7,3'-binaphthyl-1,4,1',4'-tetraone (1; Di-naphthodiospyrol D) and 5',8'-dihydroxy-5,8-dimethoxy-6,6'-dimethyl-7,3'-binaphthyl-1,4,1',4'-tetraone (2; Di-naphthodiospyrol E), along with known naphthoquinones diospyrin (3) and 8-hydroxy diospyrin (4) were isolated from the chloroform fraction of extract of Diospyros lotus roots. Their structures were elucidated by advanced spectroscopic analyses, including HSQC, HMBC, NOESY, and J-resolved NMR experiments. The fractions and compounds 1-4 were evaluated for urease activity and phosphodiesterase-I, carbonic anhydrase-II and α-chymotrypsin enzyme inhibitory activities. Compounds 1 and 2 and their corresponding fractions showed significant and selective inhibitory effects on urease activities. The IC₅₀ values of 1 and 2 were 260.4 ± 6.37 and 381.4 ± 4.80 µmol·L^-1, respectively, using thiourea (IC₅₀ = 21 ± 0.11 µmol·L^-1) as the standard inhibitor. This was the first report demonstrating that the naphthoquinones class showed urease inhibition.

Diospyros assimilis root extract assisted biosynthesised silver nanoparticles and their evaluation of antimicrobial activity

The current research study focuses on biosynthesis of silver nanoparticles (Ag NPs) for the first time from silver acetate employing methanolic root extract of Diospyros assimilis . The UV–Vis absorption spectrum of biologically synthesised nanoparticles displayed a surface plasmon peak at 428 nm indicating the formation of Ag NPs. The influence of metal ion concentration, reaction time and amount of root extract in forming Ag NPs by microscopic and spectral analysis was thoroughly investigated. Structural analysis from transmission electron microscopy confirmed the nature of metallic silver as face‐centered cubic (FCC) crystalline with an average diameter of 17 nm, which correlates with an average crystallite size (19 nm) calculated from X‐ray diffraction analysis. Further, the work was extended for the preliminary examination of antimicrobial activity of biologically synthesised Ag NPs that displayed promising activity against all the tested pathogenic strains.

Diospyros, an under-utilized, multi-purpose plant genus: A review

The genus Diospyros from family Ebenaceae has versatile uses including edible fruits, valuable timber, and ornamental uses. The plant parts of numerous species have been in use as remedies in various folk healing practices, which include therapy for hemorrhage, incontinence, insomnia, hiccough, diarrhea etc. Phytochemical constituents such as terpenoids, ursanes, lupanes, polyphenols, tannins, hydrocarbons, and lipids, benzopyrones, naphthoquinones, oleananes, and taraxeranes have been isolated from different species of this genus. The biological activities of these plants such as antioxidant, anti-inflammatory, analgesic, antipyretic, anti-diabetic, antibacterial, anthelmintic, antihypertensive, cosmeceutical, enzyme-inhibitory etc. have been validated by means of an in vitro, in vivo, and clinical tests. As a rich reserve of pharmacologically important components, this genus can accelerate the pace of drug discovery. Accordingly, the aim of the present review is to survey and summarize the recent literature pertaining to the medicinal and pharmacological uses of Diospyros, and to select experimental evidence on the pharmacological properties of this genus. In addition, the review also aims at identifying areas that need development to make use of this genus, especially its fruit and phytochemicals as means for economic development and for drug discovery.

Inhibitory effects of compounds from Phyllanthus amarus on nitric oxide production, lymphocyte proliferation, and cytokine release from phagocytes

Standardized extract of Phyllanthus amarus has previously been shown to have a strong inhibitory effect on phagocytic activity of human neutrophils. The current study was carried out to evaluate the effects of constituents of the extract of P. amarus on nitric oxide (NO) production as well as lymphocyte proliferation and cytokine release from phagocytes. Three compounds, ethyl 8-hydroxy-8-methyl-tridecanoate, 7β,19α dihydroxy-urs-12-ene, and 1,7,8-trihydroxy-2-naphtaldehyde, together with seven known compounds were isolated from the whole plant of P. amarus. The isolated compounds and reference standards, ie, gallic acid, ellagic acid, corilagin, and geraniin, which were quantitatively analyzed in the extracts, were evaluated for their effects on immune cells. Among the compounds tested, the lignans, especially phyltetralin and phyllanthin, showed strong inhibition on lymphocyte proliferation with half maximal inhibitory concentration (IC₅₀) values of 1.07 μM and 1.82 μM, respectively. Ethyl 8-hydroxy-8-methyl-tridecanoate and 1,7,8-trihydroxy-2-naphtaldehyde exhibited strong inhibition on nitric oxide production with IC₅₀ values of 0.91 μM and 1.07 μM, respectively. Of all the compounds, corilagin was the strongest inhibitor of tumor necrosis factor-α release with an IC₅₀ value of 7.39 μM, whereas geraniin depicted the strongest inhibitory activity on interleukin-1β release with an IC₅₀ value of 16.41 μM. The compounds constituting the extract of P. amarus were able to inhibit the innate immune response of phagocytes at different steps.

A Rare Class of New Dimeric Naphthoquinones from Diospyros lotus have Multidrug Reversal and Antiproliferative Effects

Three new dimeric naphthoquinones, 5,4′-dihydroxy-1′-methoxy-6,6′-dimethyl-7,3′-binaphthyl-1,4,5′,8′-tetraone (1), 5′,8′-dihydroxy-5-methoxy-6,6′-dimethyl-7,3′-binaphthyl-1,4,1′,4′-tetraone (2) and 8,5′,8′-trihydroxy-6,6′-dimethyl-7,3′-binaphthyl-1,4,1′,4′-tetraone (3), were isolated from the roots of Diospyros lotus. Their structures were elucidated by spectroscopic techniques, including 1D and 2D NMR, such as HSQC, HMBS, NOESY, and J-resolved. Compounds 1–3 were evaluated for their effects on the reversion of multidrug resistance (MDR) mediated by P-glycoprotein through use of the rhodamine-123 exclusion screening test on human ABCB1 gene transfected L5178Y mouse T-cell lymphoma. Compounds 1–3 were also assessed for their antiproliferative and cytotoxic effects on L5178 and L5178Y mouse T-cell lymphoma lines. Both 1 and 2 exhibited promising antiproliferative and MDR-reversing effects in a dose-dependent manner. The effects of the tested compounds on the activity of doxorubicin were observed to vary from slight antagonism to antagonism.

Phytochemical, spectroscopic and density functional theory study of Diospyrin, and non-bonding interactions of Diospyrin with atmospheric gases

Density functional theory (DFT) and phytochemical study of a natural product, Diospyrin (DO) have been carried out. A suitable level of theory was developed, based on correlating the experimental and theoretical data. Hybrid DFT method at B3LYP/6-31G (d,p) level of theory is employed for obtaining the electronic, spectroscopic, inter-molecular interaction and thermodynamic properties of DO. The exact structure of DO is confirmed from the nice validation of the theory and experiment. Non-covalent interactions of DO with different atmospheric gases such as NH3, CO2, CO, and H2O were studied to find out its electroactive nature. The experimental and predicted geometrical parameters, IR and UV-vis spectra (B3LYP/6-31+G (d,p) level of theory) show excellent correlation. Inter-molecular non-bonding interaction of DO with atmospheric gases is investigated through geometrical parameters, electronic properties, charge analysis, and thermodynamic parameters. Electronic properties include, ionization potential (I.P.), electron affinities (E.A.), electrostatic potential (ESP), density of states (DOS), HOMO, LUMO, and band gap. All these characterizations have corroborated each other and confirmed the presence of non-covalent nature in DO with the mentioned gases.

Synthesis, molecular docking and biological evaluation of novel 6-(4-(4-aminophenylsulfonyl)phenylamino)-5H-benzo[a]phenothiazin-5-one derivatives

A novel series of 6-(4-(4-aminophenylsulfonyl)phenylamino)-5H-benzo[a]phenothiazin-5-one derivatives have been synthesized and examined for their in vitro antibacterial activity against a panel of Gram-positive and Gram-negative bacteria. Among these, N-(4-(4-(5-oxo-5H-benzo[a]phenothiazin-6-ylamino)phenylsulfonyl)phenyl)-3,5-bis(trifluoromethyl)benzamide (3n) (0.4 μg/mL) and 4-ethyl-N-(4-(4-(5-oxo-5H-benzo[a]phenothiazin-6-ylamino)phenylsulfonyl)phenyl)benzamide (3l) (0.6 μg/mL) systems exhibited a potent inhibitory activity against Gram-positive organism Bacillus subtilis, when compare to the other synthesized compounds. Sparfloxacin (9.76 μg/mL), Norfloxacin (no activity) were employed as the standard drugs. An evaluation of the cytotoxicity of the title compounds (1, 2, 3a-n) revealed that they displayed low toxicity (26-115 mg/L) against cervical cancer cell line (SiHa). The results of these studies suggest that, phenothiazin-5-one derivatives are interesting binding agents for the development of new Gram-positive and Gram-negative antibacterial agents. To understand the interactions with protein receptors, docking simulation was done with crystal structures of B.subtilis (YmaH) and histone deacetylase (HDAC8) to determine the probable binding conformation.

CuO/I2-mediated intramolecular annulation for the synthesis of 2-aroyl-3-hydroxy-4-iodonaphthalenes

A novel method for the direct synthesis of 2-aroyl-3-hydroxy-4-iodonaphthalenes has been developed via CuO/I₂-mediated domino reactions.

Identification of unusual C–Cl⋯π contacts in 2-(alkylamino)-3-chloro-1,4-naphthoquinones: effect of N-substituents on crystal packing, fluorescence, redox and anti-microbial properties

XRD study demonstrates the opening of unusual C–Cl⋯π synthon in 2-(alkylamino)-3-chloro-1,4-naphthoquinone. Notably, compound holding N-pyridylmethyl exhibits enhanced activity against S. aureus and proved to be more potent than ciprofloxacin.

Antileishmanial Potential of Tropical Rainforest Plant Extracts

A total of 115 different plant extracts from our collection, representing 96 plant species, have been evaluated for in vitro antileishmanial activity against L. amazonensis promastigotes. In addition, the extracts were screened for cytotoxic activity against BALB/c mouse macrophages in order to assess a selectivity index. Crude extracts that showed a selectivity index (CC50 for macrophage / IC50 for promastigotes) ³ 5 or with IC50 < 12.5 μg/mL against promastigotes, a total of 28 extracts, were further screened for anti-amastigote activity. A total of 25 extracts showed promising activity against L. amazonensis promastigotes with low cytotoxic activity. Ten of these extracts showed selectivity indices, (CC50 for macrophages / IC50 for amastigotes) greater than 10 and are considered "hits", worthy candidates for further phytochemical exploration: Conostegia xalapensis methanol bark extract, Endiandra palmerstonii bark extract, Eugenia monteverdensis acetone bark extract, Eugenia sp. "fine leaf" acetone bark extract, Exothea paniculata chloroform bark extract, Mallotus paniculatus ethanol bark extract, Matelea pseudobarbata ethanol extract, Quercus insignis ethanol bark extract, Sassafras albidum dichloromethane bark extract, and Stemmadenia donnell-smithii acetone bark extract.

Trypanosomatids topoisomerase re-visited. New structural findings and role in drug discovery

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There is an urgent need of new treatments against trypanosomatids-borne diseases.

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DNA topoisomerases are pointed as potential drug targets against unicellular parasites.

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Trypanosomatids have a full set of DNA topoisomerases in both nucleus and kinetoplast.

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TopII and TopIII are located in the kinetoplast and fully involved in kDNA replication.

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Tritryps TopIB differ in structure from mammalian’s pointing to an attractive target.

The Trypanosomatidae family, composed of unicellular parasites, causes severe vector-borne diseases that afflict human populations worldwide. Chagas disease, sleeping sickness, as well as different sorts of leishmaniases are amongst the most important infectious diseases produced by Trypanosoma cruzi, Trypanosoma brucei and Leishmania spp., respectively. All these infections are closely related to weak health care services in low-income populations of less developed and least economically developed countries. Search for new therapeutic targets in order to hit these pathogens is of paramount priority, as no effective vaccine is currently in use against any of these parasites. Furthermore, present-day chemotherapy comprises old-fashioned drugs full of important side effects. Besides, they are prone to produce tolerance and resistance as a consequence of their continuous use for decades. DNA topoisomerases (Top) are ubiquitous enzymes responsible for solving the torsional tensions caused during replication and transcription processes, as well as in maintaining genomic stability during DNA recombination. As the inhibition of these enzymes produces cell arrest and triggers cell death, Top inhibitors are among the most effective and most widely used drugs in both cancer and antibacterial therapies. Top relaxation and decatenation activities, which are based on a common nicking–closing cycle involving one or both DNA strands, have been pointed as a promising drug target. Specific inhibitors that bind to the interface of DNA-Top complexes can stabilize Top-mediated transient DNA breaks. In addition, important structural differences have been found between Tops from the Trypanosomatidae family members and Tops from the host. Such dissimilarities make these proteins very interesting for drug design and molecular intervention. The present review is a critical update of the last findings regarding trypanosomatid’s Tops, their new structural features, their involvement both in the physiology and virulence of these parasites, as well as their use as promising targets for drug discovery.

Synthesis, molecular docking and antibacterial evaluation of new 1,4-naphthoquinone derivatives contains carbazole-6,11-dione moiety

A new series of new 1,4-naphthoquinone derivatives containing carbazole-6,11-dione moiety, which has not been reported yet, has been synthesized from 1,4-naphthoquinone and 4-aminophenylsulfone involving a Michael addition, benzoylation, and Pd-catalyzed coupling. This set of compounds has been evaluated for in vitro antibacterial studies against different Gram-positive and Gram-negative bacteria, and most of the synthesized compounds exhibited good antibacterial activity and the minimum inhibitory concentrations (MICs) are compared with the standard drugs used. Compound 7 exhibited good antibacterial activity among all the molecules studied with the best MIC of 2.1 μg/mL against Bacillus subtilis. To understand the molecular interactions with targeted proteins, the molecular docking of all the synthesized compounds were carried out; between 14 molecules docked, compound 7 was the one with the best glide and E model score of -7.73 and -95.37, respectively. In all docked molecules, compound 5 exhibited least glide and E model score of -4.55 and -101.56, respectively. Figureᅟ

Modification of phospholipid bilayers induced by sulfurated naphthoquinones

New thionaphthoquinones and their hydroxyl derivatives, bearing alkyl side chains that match the phospholipids POPC and POPE, were synthesized in order to investigate their interactions with lipids. It was observed that, in general, these additives destabilize the lipid bilayer and induce less organized structures with higher curvature, in particular the induction of an hexagonal phase on aqueous POPC mixtures. Moreover, cubic phases, not normally observed in the pure lipids when fully hydrated, were detected. Coexistence of lamellar phases was interpreted as a consequence of microsegregation of the components in the mixtures. These results are in line with previous observations on the effect of structurally similar (hydro)quinones in phase behavior of these lipids.

Anti-protozoal activity of aporphine and protoberberine alkaloids from Annickia kummeriae (Engl. & Diels) Setten & Maas (Annonaceae)

BACKGROUND

Malaria, trypanosomiasis and leishmaniasis have an overwhelming impact in the poorest countries in the world due to their prevalence, virulence and drug resistance ability. Currently, there is inadequate armory of drugs for the treatment of malaria, trypanosomiasis and leishmaniasis. This underscores the continuing need for the discovery and development of new anti-protozoal drugs. Consequently, there is an urgent need for research aimed at the discovery and development of new effective and safe anti-plasmodial, anti-trypanosomal and anti-leishmanial drugs.

METHODS

Bioassay-guided chromatographic fractionation was employed for the isolation and purification of antiprotozoal alkaloids.

RESULTS

The methanol extract from the leaves of Annickia kummeriae from Tanzania exhibited a strong anti-plasmodial activity against the multi-drug resistant Plasmodium falciparum K1 strain (IC50 0.12 ± 0.01 μg/ml, selectivity index (SI) of 250, moderate activity against Trypanosoma brucei rhodesiense STIB 900 strain (IC50 2.50 ± 0.19 μg/ml, SI 12) and mild activity against Leishmania donovani axenic MHOM-ET-67/82 strain (IC50 9.25 ± 0.54 μg/ml, SI 3.2). Bioassay-guided chromatographic fractionation led to the isolation of four pure alkaloids, lysicamine (1), trivalvone (2), palmatine (3), jatrorrhizine (4) and two sets of mixtures of jatrorrhizine (4) with columbamine (5) and palmatine (3) with (-)-tetrahydropalmatine (6). The alkaloids showed low cytotoxicity activity (CC50 30 - >90 μg/ml), strong to moderate anti-plasmodial activity (IC50 0.08 ± 0.001 - 2.4 ± 0.642 μg/ml, SI 1.5-1,154), moderate to weak anti-trypanosomal (IC50 2.80 ± 0.001 - 14.3 ± 0.001 μg/ml, SI 2.3-28.1) and anti-leishmanial activity IC50 2.7 ± 0.001 - 20.4 ± 0.003 μg/ml, SI 1.7-15.6).

CONCLUSION

The strong anti-plasmodial activity makes these alkaloids good lead structures for drug development programs.

Leishmanicidal activities and cytotoxicities of bisnaphthoquinone analogues and naphthol derivatives from Burman Diospyros burmanica

A methanol extract of the wood of Diospyros burmanica, collected in Burma (Myanmar), was found to exhibit significant activity against Leishmania major. Subsequent chromatographically resolved fractionation led to the isolation of three novel bisnaphthoquinone analogues, burmanin A, B, and C (1-3), together with nine known compounds (4-12). The structure of 1 was confirmed by X-ray crystallography, and those of 2 and 3 by spectroscopic techniques, including 1D and 2D NMR. The inhibitory activities of the isolates were evaluated against the promastigote forms of Leishmania major and the murine macrophage-like cell line, RAW264.7.

Reviews on 1,4-naphthoquinones from Diospyros L

The genus Diospyros is one of the most important sources of bioactive compounds, exclusively 1,4-naphthoquinones. The following information is an attempt to cover the developments in the biology and phytochemistry of 1,4-naphthoquinones isolated from this genus, as well as the studies done and the suggested mechanisms regarding their activities. During the past 60 years, many of these agents have been isolated from Diospyros L. Twelve considerable bioactive structures are reported in this review. The basic 1,4-naphthoquinone skeletons, on which a large number of studies have been done, are plumbagin and diospyrin. Today, the potential for development of leads from 1,4-naphthoquinones obtained from Diospyros L. is growing dramatically, mainly in the area of anticancer and antibacterial investigations. The data prepared and described here are intended to be served as a reference tool to the natural products and chemistry specialists in order to expand the rational drug design.

Encecalol angelate, an unstable chromene from Ageratum conyzoides L.: total synthesis and investigation of its antiprotozoal activity

ETHNOPHARMACOLOGICAL RELEVANCE

In agreement with ethnomedicinal reports, the dichloromethane extract of Ageratum conyzoides L. (Asteraceae) was recently shown to be of considerable activity against Trypanosoma brucei rhodesiense, the etiologic agent of East African Human Trypanosomiasis (East African Sleeping Sickness). Isolated compounds, namely, methoxylated flavonoids as well as the chromene derivative encecalol methyl ether, were less active than the crude extract. The activity of the extract was found to decrease considerably while stored in solution. An unstable compound was detected in the fresh extract by HPLC, which was converted rapidly into the encecalol methyl ether while stored in methanolic solution. This compound, deemed to represent a constituent with antitrypanosomal activity, could not be isolated from the extract in intact form.

AIM OF THE STUDY

To elucidate the structure of this unstable compound and to investigate its potential role in the antitrypanosomal activity of the total extract.

MATERIALS AND METHODS

UHPLC/ESI-qQTOF MSMS and NMR data of the degraded product indicated its chemical identity as encecalol angelate (1) which was therefore prepared by total synthesis via a linear six steps synthesis, starting from resorcinol and 2-methylbut-3-en-2-ol.

RESULTS

Total synthesis, in an overall yield of 15%, led to pure 1, which was chromatographically and spectroscopically identical with the natural product. The compound degraded in methanol with a half-life of approximately 6h to yield encecalol methyl ether (2). The antiprotozoal activity of synthetic encecalol angelate against T. brucei rhodesiense as well as T. cruzi, Leishmania donovani and Plasmodium falciparum was investigated and found to be quite low.

CONCLUSIONS

The synthetic approach applied here for the first time also provides access to the related bioactive chromenes encecalin (7) and encecalol (8) with improved yields compared with reported methods. Encecalol angelate, however, is most likely not responsible for the high antitrypanosomal activity of the freshly prepared dichloromethane extract of A. conyzoides.

Screening medicinal plants for the detection of novel antimalarial products applying the inhibition of β-hematin formation

The identification of novel scaffolds for the development of effective and safe treatments to fight malaria is urgently needed. One of the main opportunities is the discovery of new molecules from natural origin. A simple, robust and cost-effective colorimetric assay based on the inhibition of β-hematin has been adapted to routinely screen plant extracts with the ultimate goal to identify novel antimalarial ingredients. The development of this assay has included a careful optimization of all critical experimental parameters. The β-hematin assay can be completed in less than one working day, requiring a 96-well UV-vis plate reader and low-cost commercially available reagents using a standard operating protocol. It can be used on its own or in combination with the well-known Plasmodium growth inhibition assay and has the obvious merit to be informative at the early stage of drug discovery regarding the mechanism of action of the actives. A total of 40 diverse natural products and 219 plants extracts were tested. Good correlations in respect with specificity (pure compounds 85%, extracts 93%) and positive predictive value (pure compounds 72%, extracts 50%) were obtained in comparison with Plasmodium growth inhibition assay that was used as the reference assay.

Genetic reconstruction of protozoan rRNA decoding sites provides a rationale for paromomycin activity against Leishmania and Trypanosoma

Aminoglycoside antibiotics target the ribosomal decoding A-site and are active against a broad spectrum of bacteria. These compounds bind to a highly conserved stem-loop-stem structure in helix 44 of bacterial 16S rRNA. One particular aminoglycoside, paromomycin, also shows potent antiprotozoal activity and is used for the treatment of parasitic infections, e.g. by Leishmania spp. The precise drug target is, however, unclear; in particular whether aminoglycoside antibiotics target the cytosolic and/or the mitochondrial protozoan ribosome. To establish an experimental model for the study of protozoan decoding-site function, we constructed bacterial chimeric ribosomes where the central part of bacterial 16S rRNA helix 44 has been replaced by the corresponding Leishmania and Trypanosoma rRNA sequences. Relating the results from in-vitro ribosomal assays to that of in-vivo aminoglycoside activity against Trypanosoma brucei, as assessed in cell cultures and in a mouse model of infection, we conclude that aminoglycosides affect cytosolic translation while the mitochondrial ribosome of trypanosomes is not a target for aminoglycoside antibiotics.

Rational design of novel therapeutics relies on the knowledge and understanding of potential drug targets. Historically, the majority of therapeutics have not been rationally designed, but empirically discovered. Paromomycin, an aminoglycoside with antibacterial activity, has been found to show considerable activity against leishmaniasis, a disease caused by the protozoan parasite Leishmania. However, the mechanisms of aminoglycoside action against protozoan parasites have in part remained unclear. In this study we demonstrate that the cytosolic ribosome is the preferred drug target, and that the mitochondrial ribosome does not contribute to the antiprotozoal activity of aminoglycosides. As the cytosolic ribosome of Trypanosoma, the causative agent of sleeping sickness and Chagas disease, resembles that of Leishmania, we tested the efficacy of paromomycin against Trypanosoma. We found that paromomycin not only inhibits the growth of Trypanosoma in culture, but also suppresses trypanosomiasis in a mouse infection model. Our results point to the cytosolic ribosome as a promising drug target for antiprotozoal drug development.

Novel diamidines with activity against Babesia divergens in vitro and Babesia microti in vivo

Dicationic diamidines, such as diminazene and pentamidine, are well-studied chemotherapeutic agents with significant activity against parasitic diseases. The in vitro activities of novel diamidine compounds against the Babesia divergens strains 1903B and 4201 were investigated. The most potent compound, a diphenyl furan, had a 50% inhibitory concentration (IC(50)) of 1.5 ng/ml. In a murine model, several test compounds were effective enough to cure mice infected with Babesia microti at a dose of 12.5 and/or 25 mg/kg of body weight given by the subcutaneous route for 4 days. The best antibabesial properties were exhibited by terphenyls, benzimidazoles, diphenyl furans, pentamidine, and pentamidine analogues.