Myristicyclins A and B: antimalarial procyanidins from Horsfieldia spicata from Papua New Guinea

Investigations of Antibacterial, Antioxidant, and Antidiabetic Potential of Extract and Its Active Fractions from the Leaves of Horsfieldia spicata (Roxb.) J. Sinclair

This study was undertaken to analyse the potential bioactivities including antibacterial, antioxidant and antidiabetic derived from the methanolic extract and the column chromatography ethyl acetate fraction (AcOEt Fr) of Horsfieldia spicata leaves. Methanolic extract and 4 other fractions was calculated for total phenol and flavonoid contents along with tested for antibacterial, antioxidant and antidiabetic properties. Interestingly, the AcOEt Fr had the highest value for total flavonoid content and the best antioxidant, and antidiabetic activities. Therefore, the AcOEt Fr was further separated using column chromatography technique for obtaining 9 selected fractions namely fraction 1 (F1) - fraction 9 (F9) which were further tested. The results showed that the AcOEt column chromatography fractions namely F2, F3, F4 and F6 had the best clear inhibition antibacterial value against all bacterial tested. In addition, these fractions also exhibited better Minimum Inhibitory Concentrations (MIC) and Minimum Bactericidal Concentrations (MBC) values than others. Antioxidant, 2,2-diphenylpicrylhydrazyl (DPPH) assayed indicated that AcOEt Fr had the strongest IC50 value of 47.30 μg/mL. Further, F4 column chromatography fraction showed the best inhibition against α-Glucosidase enzyme related to antidiabetic activity with an IC50 value of 6.11 μg/mL. Liquid chromatography tandem-mass spectrometry (LC/MS/MS) analysis identified that F4 derived from AcOEt fraction had several compounds belonging to the flavonoid and phenolics such as 3',5-dihydroxy-7,4'-dimethoxyflavone, 5,7-dihydroxy-3-(4'-hydroxybenzyl)chromone, and Kadsurenin I.

Recent advances in the synthesis of natural products containing the phloroglucinol motif

Covering: June 2009 to 2021Natural products containing a phloroglucinol motif include simple and oligomeric phloroglucinols, polycyclic polyprenylated acylphloroglucinols, phloroglucinol-terpenes, xanthones, flavonoids, and coumarins. These compounds represent a major class of secondary metabolites which exhibit a wide range of biological activities such as antimicrobial, anti-inflammatory, antioxidant and hypoglycaemic properties. A number of these compounds have been authorized for therapeutic use or are currently being studied in clinical trials. Their structural diversity and utility in both traditional and conventional medicine have made them popular synthetic targets over the years. In this review, we compile and summarise the recent synthetic approaches to the natural products bearing a phloroglucinol motif. Focus has been given on ingenious strategies to functionalize the phloroglucinol moiety at multiple positions. The isolation and bioactivities of the compounds are also provided.

Acid-catalysed iterative generation of o-quinone methides for the synthesis of dioxabicyclo[3.3.1]nonanes: total synthesis of myristicyclins A-B

We report a practical and efficient method for the synthesis of bioactive flavanoids relying on the strategic use of o-quinine methide (o-QM) intermediates. This involves Brønsted acid-catalysed iterative generation of o-QMs/[4+2] cycloaddition/intermolecular Michael addition/cyclative acetalization in a cascade sequence for the synthesis of dioxabicyclo[3.3.1]nonanes. The 'one-pot', controlled cascade sequence successfully provided the shortest route amenable for gram scale synthesis of natural products (±)-myristicyclins A-B.

Nutmegs and wild nutmegs: An update on ethnomedicines, phytochemicals, pharmacology, and toxicity of the Myristicaceae species

Prized medicinal spice true nutmeg is obtained from Myristica fragrans Houtt. Rest species of the family Myristicaceae are known as wild nutmegs. Nutmegs and wild nutmegs are a rich reservoir of bioactive molecules and used in traditional medicines of Europe, Asia, Africa, America against madness, convulsion, cancer, skin infection, malaria, diarrhea, rheumatism, asthma, cough, cold, as stimulant, tonics, and psychotomimetic agents. Nutmegs are cultivated around the tropics for high-value commercial spice, used in global cuisine. A thorough literature survey of peer-reviewed publications, scientific online databases, authentic webpages, and regulatory guidelines found major phytochemicals namely, terpenes, fatty acids, phenylpropanoids, alkanes, lignans, flavonoids, coumarins, and indole alkaloids. Scientific names, synonyms were verified with www.theplantlist.org. Pharmacological evaluation of extracts and isolated biomarkers showed cholinesterase inhibitory, anxiolytic, neuroprotective, anti-inflammatory, immunomodulatory, antinociceptive, anticancer, antimicrobial, antiprotozoal, antidiabetic, antidiarrhoeal activities, and toxicity through in-vitro, in-vivo studies. Human clinical trials were very few. Most of the pharmacological studies were not conducted as per current guidelines of natural products to ensure repeatability, safety, and translational use in human therapeutics. Rigorous pharmacological evaluation and randomized double-blind clinical trials are recommended to analyze the efficacy and therapeutic potential of nutmeg and wild nutmegs in anxiety, Alzheimer's disease, autism, schizophrenia, stroke, cancer, and others.

Chemical composition of three Malaysian Horsfieldia essential oils

This study aims to assess the chemical compositions of the essential oils from three Horsfieldia species namely H. fulva Warb., H. sucosa Warb. and H. superba Warb., which are found in Malaysia. The essential oils were derived from the samples through hydrodistillation which were then characterised by gas chromatography (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Based on the findings, the H. fulva, H. sucosa and H. superba essential oils represented 98.2%, 98.7% and 98.5% of the total oils, respectively. The major component of H. fulva oil was identified to be germacrene D (20.8%), H. sucosa oil mainly contained α-cadinol (17.5%), whereas H. superba oil was rich in δ-cadinene (18.2%). To the best of our knowledge, this is the first study of the composition of the essential oils from these selected Horsfieldia species.

Synthesis and antiproliferative activity of 6-naphthylpterocarpans

The Heck-oxyarylation of racemic 2-(1-naphthyl)- and 2-(2-naphthyl)-2H-chromene derivatives were carried out resulting diastereoselectively in (6S*,6aR*,11aR*)-6-(1-naphthyl)- and 6-(2-naphthyl)-pterocarpans as major products and bridged (6R*,12R*)-6,12-methanodibenzo[d,g][1,3]dioxocine derivatives as minor products. Antiproliferative activity of two 6-naphthylpterocarpans was identified by MTT assay against A2780 and WM35 human cancer cell lines with low micromolar IC50 values. The measured 0.80 and 3.51 μM IC50 values of the (6S*,6aR*,11aR*)-6-(1-naphthyl)pterocarpan derivative with 8,9-methylenedioxy substitution represent the best activities in the pterocarpan family. Enantiomers of the pterocarpan and dioxocine derivatives and their chiral 2-naphthylchroman-4-one and 2-naphthyl-2H-chromene precursors were separated by HPLC using chiral stationary phase. HPLC-ECD spectra were recorded and absolute configuration and low-energy solution conformations were determined by TDDFT-ECD calculations. Characteristic ECD transitions of the separated enantiomers were correlated with their absolute configuration.

Flavonoids as efficient scaffolds: Recent trends for malaria, leishmaniasis, Chagas disease, and dengue

Endemic in 149 tropical and subtropical countries, neglected tropical diseases (NTDs) affect more than 1 billion people annually with over 500,000 deaths. Among the NTDs, some of the most severe consist of leishmaniasis, Chagas disease, and dengue. The impact of the combined NTDs closely rivals that of malaria. According to the World Health Organization, 216 million cases of malaria were reported in 2016 with 445,000 deaths. Current treatment options are associated with various limitations including widespread drug resistance, severe adverse effects, lengthy treatment duration, unfavorable toxicity profiles, and complicated drug administration procedures. Flavonoids are a class of compounds that has been the subject of considerable scientific interest. New developments of flavonoids have made promising advances for the potential treatment of malaria, leishmaniasis, Chagas disease, and dengue, with less toxicity, high efficacy, and improved bioavailability. This review summarizes the current standings of the use of flavonoids to treat malaria and neglected diseases such as leishmaniasis, Chagas disease, and dengue. Natural and synthetic flavonoids are leading compounds that can be used for developing antiprotozoal and antiviral agents. However, detailed studies on toxicity, pharmacokinetics, and mechanisms of action of these compounds are required to confirm the in vitro pharmacological claims of flavonoids for pharmaceutical applications. HIGHLIGHTS: In the current review, we have tried to compile recent discoveries on natural and synthetic flavonoids as well as their implication in the treatment of malaria, leishmaniasis, Chagas disease, and dengue. A total of 373 (220 natural and 153 synthetic) flavonoids have been evaluated for antimalarial, antileishmanial, antichagasic, and antidengue activities. Most of these flavonoids showed promising results against the above diseases. Reports on molecular modeling of flavonoid compounds to the disease target indicated encouraging results. Flavonoids can be prospected as potential leads for drug development; however, more rigorously designed studies on toxicity and pharmacokinetics, as well as the quantitative structure-activity relationship studies of these compounds, need to be addressed.

Diarylpropanes from Horsfieldia kingii

Three new diarylpropanes (1-3), including two diarylpropane glycosides, and three known ones, were isolated from 70% aqueous acetone extract of the twigs and leaves of Horsfieldia kingii. Their structures were elucidated by spectroscopic analysis. Bioactive evaluation of inhibition on DDC enzyme assay showed that the new compounds were inactive.

First synthesis of (±)-myristicyclin A

The first synthesis of myristicyclin A, which was isolated from the Papua New Guinean plant Horsfieldia spicata, is described. The synthesis features acid-mediated hydroarylation reaction to form a dihydrocoumarin moiety, construction of the 2,8-dioxabicyclo[3.3.1]nonane skeleton under acidic conditions, and regioselective Friedel-Crafts acylation at a later stage.

Enantioselective Multicomponent Condensation Reactions of Phenols, Aldehydes, and Boronates Catalyzed by Chiral Biphenols

Chiral diols and biphenols catalyze the multicomponent condensation reaction of phenols, aldehydes, and alkenyl or aryl boronates. The condensation products are formed in good yields and enantioselectivities. The reaction proceeds via an initial Friedel-Crafts alkylation of the aldehyde and phenol to yield an ortho-quinone methide that undergoes an enantioselective boronate addition. A cyclization pathway was discovered while exploring the scope of the reaction that provides access to chiral 2,4-diaryl chroman products, the core of which is a structural motif found in natural products.