Total synthesis of ochnaflavone

Abstract The first total syntheses of ochnaflavone, an asymmetric biflavone consisting of apigenin and luteolin moieties, and the permethyl ether of 2,3,2'',3''-tetrahydroochnaflavone have been achieved. The key steps in the synthesis of ochnaflavone were the formation of a diaryl ether and ring cyclization of an ether-linked dimeric chalcone to assemble the two flavone nuclei. Optimal experimental conditions for the oxidative cyclization to form ochnaflavone were established. 134

Alkaloidal variation in Cissampelos capensis (Menispermaceae)

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STRUCTURE-ACTIVITY-RELATIONSHIP OF THE POLYPHENOLS INHIBITION OF α-AMYLASE AND α-GLUCOSIDASE

Background: Diabetes mellitus (DM) is a serious public health challenge, projected by WHO to be one of the 7 leading cause of death by 2030. Medicinal plants have been demonstrated to be useful in DM local management because of polyphenols present in these plants. For an alternative treatment approach especially with polyphenols-rich herbs, knowledge of comparative efficacy of the polyphenols will lead to enhanced therapy especially in postprandial hyperglyceamic control. Materials and Methods:Vegetative parts of Anacardium occidentale, Abelmoschus ecsulentus and Ceiba pentandra, prominent in the local management of DM were identified, collected and subjected to alcoholic extraction. From the crude extracts were isolated agathisflavone, quercetin 3-O-glucoside, quercetin 3-O-diglycoside, mangiferin, isomangiferin and pentagalloyl glucose, belonging to flavonoid, xanthones and tannins structural classes. These polyphenols were evaluated for their potentials to inhibit both α-glucosidase and α-amylase. Physicochemical parameters of the polyphenols were evaluated and molecular docking experiments were carried out to gain insight into the observed inhibitory activity. Results: quercetin 3-O-glucosidewas the most potent of the polyphenols against the two enzymes. Increase in the number of phenolic hydroxyl group did not increase the inhibitory activity and neither computation of the binding energies with the enzymes nor physicochemical parameters of the polyphenols could explain the observed inhibitory activity against the enzymes, across the structural classes. Thus, only the bioassay against the enzymes α-glucosidase and α-amylase correlated well with the use of the plants in treating diabetic mellitus Conclusion: Medicinal plants rich in quercetin 3-O-glycoside may have better treatment outcomes in postprandial hyperglycaemia control

1-(5,7-Dihy­droxy-2,2-dimethylchroman-6-yl)ethanone

In the title mol­ecule, C13H16O4, the pyran ring is in a half-chair conformation. There is an intra­molecular hydrogen bond involving the ketone O atom and an H atom of a phenol group which forms an S(6) ring. The ketone O atom is also involved in an inter­molecular hydrogen bond with a different phenolic H atom of a symmetry-related mol­ecule, forming C(6) chains along the c-axis direction

In vitro anti-plasmodial activity of Dicoma anomala subsp. gerrardii (Asteraceae): identification of its main active constituent, structure-activity relationship studies and gene expression profiling

<p>Abstract</p> <p>Background</p> <p>Anti-malarial drug resistance threatens to undermine efforts to eliminate this deadly disease. The resulting omnipresent requirement for drugs with novel modes of action prompted a national consortium initiative to discover new anti-plasmodial agents from South African medicinal plants. One of the plants selected for investigation was <it>Dicoma anomala </it>subsp. <it>gerrardii</it>, based on its ethnomedicinal profile.</p> <p>Methods</p> <p>Standard phytochemical analysis techniques, including solvent-solvent extraction, thin-layer- and column chromatography, were used to isolate the main active constituent of <it>Dicoma anomala </it>subsp. <it>gerrardii</it>. The crystallized pure compound was identified using nuclear magnetic resonance spectroscopy, mass spectrometry and X-ray crystallography. The compound was tested <it>in vitro </it>on <it>Plasmodium falciparum </it>cultures using the parasite lactate dehydrogenase (pLDH) assay and was found to have anti-malarial activity. To determine the functional groups responsible for the activity, a small collection of synthetic analogues was generated - the aim being to vary features proposed as likely to be related to the anti-malarial activity and to quantify the effect of the modifications <it>in vitro </it>using the pLDH assay. The effects of the pure compound on the <it>P. falciparum </it>transcriptome were subsequently investigated by treating ring-stage parasites (alongside untreated controls), followed by oligonucleotide microarray- and data analysis.</p> <p>Results</p> <p>The main active constituent was identified as dehydrobrachylaenolide, a eudesmanolide-type sesquiterpene lactone. The compound demonstrated an <it>in vitro </it>IC₅₀of 1.865 μM against a chloroquine-sensitive strain (D10) of <it>P. falciparum</it>. Synthetic analogues of the compound confirmed an absolute requirement that the α-methylene lactone be present in the eudesmanolide before significant anti-malarial activity was observed. This feature is absent in the artemisinins and suggests a different mode of action. Microarray data analysis identified 572 unique genes that were differentially expressed as a result of the treatment and gene ontology analysis identified various biological processes and molecular functions that were significantly affected. Comparison of the dehydrobrachylaenolide treatment transcriptional dataset with a published artesunate (also a sesquiterpene lactone) dataset revealed little overlap. These results strengthen the notion that the isolated compound and the artemisinins have differentiated modes of action.</p> <p>Conclusions</p> <p>The novel mode of action of dehydrobrachylaenolide, detected during these studies, will play an ongoing role in advancing anti-plasmodial drug discovery efforts.</p

Total synthesis of ochnaflavone

The first total syntheses of ochnaflavone, an asymmetric biflavone consisting of apigenin and luteolin moieties, and the permethyl ether of 2,3,2'',3''-tetrahydroochnaflavone have been achieved. The key steps in the synthesis of ochnaflavone were the formation of a diaryl ether and ring cyclization of an ether-linked dimeric chalcone to assemble the two flavone nuclei. Optimal experimental conditions for the oxidative cyclization to form ochnaflavone were established