Kneglomeratanol, kneglomeratanones A and B, and related bioactive compounds from Knema glomerata

Two New Benzoquinone Derivatives from Vietnamese Knema globularia Stems

The chemical investigation of the stems of Knema globularia led to the isolation of two new benzoquinones derivatives, embenones A and B (1 and 2), along with three known compounds (3-5). The structures of the isolated compounds were determined using spectroscopic techniques, including HRESIMS, 1D and 2D NMR, in conjunction with comparison to existing literature data. Compounds 1 and 2 represent new carbon skeletons in nature. Furthermore, all isolated compounds were evaluated for their α-glucosidase inhibitory activity, with compounds 1-3 exhibiting superior potency relative to the positive control (acarbose, IC50 331 μM). Their IC50 values ranged from 1.40 to 96.1 μM.

α-Glucosidase Inhibitors from the Stems of Knema globularia

Six new compounds, globunones A-F (1-6), and two new flavonoids (7 and 8) together with nine known compounds (9-17) were isolated from the stems of Knema globularia. The chemical structures of 1-8 were elucidated by an analysis of their NMR and high-resolution electrospray ionization mass spectrometry data as well as by comparison with literature values. The absolute configurations were determined using time-dependent density functional theory electronic circular dichroism (TD-DFT-ECD). Globunones A-E (1-5) represent the initial combined structures of a flavan-3-ol core and a 1,4-benzoquinone core. Globunone F (6) is the first flavanone-type compound bearing a 2-(2,4-dihydroxyphenyl)-2-oxoethyl group found to date in Nature. Compounds 1-3 and 6-17 were tested for their yeast α-glucosidase inhibitory activity. All compounds tested (except for 13 and 14) showed potent inhibition toward α-glucosidase with IC₅₀ values in the range 0.4-26.6 μM. Calodenin A (15) was the most active compound with an IC₅₀ value of 0.4 μM (the positive control, acarbose, IC₅₀ 93.6 μM). A kinetic analysis of 15 revealed that it is a noncompetitive inhibitor with a K_i value of 3.4 μM.

A new diarylhexane and two new diarylpropanols from the roots of Knema globularia

A new diarylhexane, kneglobularone B (1) and two new diarylpropanols, kneglobularols A - B (2 - 3) along with seven known compounds (4 - 10) were isolated and characterized from the roots of Knema globularia. It is the first time to find arylpropyl quinone (4) and isoflavone (8) in Myristicaceae family. In addition, 5 was found for the first time in Knema genus. Their structures were elucidated by UV, IR, MS, 1 D and 2 D NMR techniques. Compound 4 exhibited strong cytotoxicity against the NCI - H187 and MCF - 7 cell lines with IC₅₀ values of 3.08 and 6.68 µg/mL, respectively.

An anti-inflammatory isoflavone from soybean inoculated with a marine fungus Aspergillus terreus C23-3

A new isoflavone derivative compound 1 (psoralenone) was isolated from soybean inoculated with a marine fungus Aspergillus terreus C23-3, together with seven known compounds including isoflavones 2-6, butyrolactone I (7) and blumenol A (8). Their structures were elucidated by MS, NMR, and ECD. Psoralenone displayed moderate in vitro anti-inflammatory activity in the LPS-induced RAW264.7 cell model. Compound 2 (genistein) showed moderate acetylcholinesterase (AChE) inhibitory activity whereas compounds 2, 5 (biochanin A), 6 (psoralenol), and 7 exhibited potent larvicidal activity against brine shrimp. Compounds 3 (daidzein), 4 (4'-hydroxy-6,7-dimethoxyisoflavone), and 5-7 showed broad-spectrum anti-microbial activity, and compound 7 also showed moderate 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity.

Chemical constituents from the Knema globularia fruits and their in vitro cytotoxicity

Two new compounds, designated as knecorticosanones A-B (1-2), along with three known compounds (3-5) were isolated from the fruits of Knema globularia. Their structures were elucidated by extensive spectroscopy analysis, including 1D- and 2D-NMR, UV, IR, and HRESIMS and by comparison with the reported data in the literature. Compounds 1-5 were evaluated for their cytotoxicity. Knecorticosanone B (2) and malabaricone D (5) exhibited moderate cytotoxic effect against Hep-G2, MCF-7 and SK-LU-1 cell lines with IC₅₀ values ranging from 8.76 ± 1.02 to 18.74 ± 1.75 μM while knecorticosanone A (1), virolane (3) and 7-hydroxy-3',4'-methylenedioxyflavan (4) exhibited weak inhibitory effect against these cell lines with IC₅₀ values ranging from 25.85 ± 2.75 to 66.75 ± 2.08 μM.

Calycosin and 8-O-methylretusin isolated from Maackia amurensis as potent and selective reversible inhibitors of human monoamine oxidase-B

Nineteen compounds were isolated from the stems of Maackia amurensis by activity-guided screening for new human monoamine oxidase-B (hMAO-B) inhibitors. Among the compounds isolated, flavonoids calycosin (5) and 8-O-methylretusin (6) were found to potently and selectively inhibit hMAO-B (IC₅₀ = 0.24 and 0.23 μM, respectively) but not hMAO-A with high selectivity index (SI) values (SI = 293.8 and 81.3, respectively). In addition, 5 and 6 reversibly and competitively inhibited hMAO-B with K_i values of 0.057 and 0.054 μM, respectively. A pterocarpan (-)-medicarpin (18) was also observed to strongly inhibit hMAO-B (IC₅₀ = 0.30 μM). Most of the compounds weakly inhibited AChE, except isolupalbigenin (13) (IC₅₀ = 20.6 μM), which suggested 13 be considered a potential dual function inhibitor of MAO-B and AChE. Molecular docking simulation revealed that the binding affinities of 5 and 6 for hMAO-B (both -9.3 kcal/mol) were higher than those for hMAO-A (-7.4 and -7.2 kcal/mol, respectively). Compound 5 was found to interact by hydrogen bonding with hMAO-B at Cys172 residue (distance: 3.250 Å); no hydrogen bonding was predicted between 5 and hMAO-A. These findings suggest that compounds 5 and 6 be considered novel potent, selective, and reversible hMAO-B inhibitors and candidates for the treatment of neurological disorders.

Chemical constituents and biological activities of the fruits of Knema pachycarpa de Wilde

The n-hexane extract of Knema pachycarpa fruits (Myristicaceae family), exhibiting strong anti-acetylcholinesterase activity, was investigated by gas chromatography/mass spectrometry and then purified by column chromatography. Guided by GC/MS profiling and bioassay, chromatographic separations led to the isolation of five new compounds: two anacardic acid derivatives 1-2, two cardanol derivatives 3-4 and a cardol derivative 5, along with mixtures of known phenolic lipids 6-9. The chemical structures were determined by various spectroscopic methods. New isolated compounds 1-5 were evaluated for their cytotoxicity and anti-acetylcholinesterase activity. Cardanol 3 and cardol 5 were the most active compounds in the acetylcholinesterase inhibitory assay with IC₅₀ values of 2.60 ± 0.24 µM and 2.46 ± 0.23 µM, respectively. Cardanol 4 and cardol 5 showed moderate cytotoxicity against Hela and MCF-7 cancer cell lines with IC₅₀ values ranging from 31.36 ± 0.41 µM to 41.30 ± 2.49 µM.

New Acetophenone and Cardanol Derivatives From Knema pachycarpa

Two new acetophenone derivatives named knepachycarpanone A (1) and knepachycarpanone B (2) together with a new cardanol derivative named knepachycarpanol C (3) were isolated from the EtOAc extract of Knema pachycarpa stems. Their chemical structures were established on the basis of spectral evidences. Compounds 1 and 2 exhibited moderate cytotoxicity against Hela cancer cell line with IC50 values of 26.92 ± 1.46 and 30.20 ± 1.97 μM, respectively.

Chemical Diversity and Biological Activity of African Propolis

Natural remedies have for centuries played a significant role in traditional medicine and continue to be a unique reservoir of new chemical entities in drug discovery and development research. Propolis is a natural substance, collected by bees mainly from plant resins, which has a long history of use as a folk remedy to treat a variety of ailments. The highly variable phytochemical composition of propolis is attributed to differences in plant diversity within the geographic regions from which it is collected. Despite the fact that the last five decades has seen significant advancements in the understanding of the chemistry and biological activity of propolis, a search of the literature has revealed that studies on African propolis to date are rather limited. The aim of this contribution is to report on the current body of knowledge of African propolis, with a particular emphasis on its chemistry and biological activity. As Africa is a continent with a rich flora and a vast diversity of ecosystems, there is a wide range of propolis phytochemicals that may be exploited in the development of new drug scaffolds.

Anacardic Acids from Knema hookeriana as Modulators of Bcl-xL/Bak and Mcl-1/Bid Interactions

Proteins of the Bcl-2 family are key targets in anticancer drug discovery. Disrupting the interaction between anti- and pro-apoptotic members of this protein family was the approach chosen in this study to restore apoptosis. Thus, a biological screening on the modulation of the Bcl-xL/Bak and Mcl-1/Bid interactions permitted the selection of Knema hookeriana for further phytochemical investigations. The ethyl acetate extract from the stem bark led to the isolation of six new compounds, three acetophenone derivatives (1-3) and three anacardic acid derivatives (4-6), along with four known anacardic acids (7-10) and two cardanols (11, 12). Their structures were elucidated by 1D and 2D NMR analysis in combination with HRMS experiments. The ability of these compounds to antagonize Bcl-xL/Bak and Mcl-1/Bid association was determined, using a protein-protein interaction assay, but only anacardic acid derivatives (4-10) exhibited significant binding properties, with Ki values ranging from 0.2 to 18 μM. Protein-ligand NMR experiments further revealed that anacardic acid 9, the most active compound, does not interact with the anti-apoptotic proteins Bcl-xL and Mcl-1 but instead interacts with pro-apoptotic protein Bid.

Acetate-Derived Metabolites from the Brown Alga Lobophora variegata

Seven new nonadecaketides (1-7), lobophorols A-C, lobophopyranones A and B, and lobophorones A and B, along with the first naturally occurring related metabolites (8-10), were isolated from specimens of Lobophora variegata collected from the Canary Islands. Their structures were determined by extensive spectroscopic methods. In addition, an insight into the biosynthesis of these compounds on the basis of the involvement of type III polyketide synthases is proposed. Lobophorol A (1) showed significant antibacterial activity against Staphylococcus aureus.

A new acyclic diterpene acid and bioactive compounds from Knema glauca

Investigation of the chemical constituents of the fruits of Knema glauca (Myristicaceae) yielded a new acyclic diterpene acid, named glaucaic acid 4, together with four acylphenols, including 1-(2,6-dihydroxyphenyl) tetradecan-1-one 1, malabaricone A 6, dodecanoylphloroglucinol 7 and 1-(2,4,6-trihydroxyphenyl)-9-phenylnonan-1-one 8, two lignans sesamin 2 and asarinin 3, and a flavan, myristinin D 5. In addition, myristinin A 9 and (+/-)-7,4'-dihydroxy-3'-methoxyflavan 10 were isolated from its leaves and stems, respectively. When tested against small-cell lung cancer (NCI-H187), epidermoid carcinoma (KB) and breast cancer (BC) cell lines, compounds 1, 6-8 and 10 displayed weak to moderate cytotoxicity. The acylphenols 6-8 displayed antituberculosis activity against the microbe Mycobacterium tuberculosis with MIC values of 25, 50 and 100 microg/mL, respectively, and antiviral activity against herpes simplex virus type 1, with 7 as the most active compound (IC(50) = 3.05 microg/mL). Malabaricone A 6 was also active against the malarial parasite Plasmodium falciparum with an IC(50) value of 2.78 microg/mL.

Four New Compounds from the Leaves ofAcer truncatum

Four new compounds, 3-(4-hydroxy-3,5-dimethoxyphenyl)propyl formate (1), 2,6-dimethoxy-4-[(1S)-3-methoxypropyl]phenol (2), (1R,2R)-4-[(3R)-3-hydroxybutyl]-3,3,5-trimethylcyclohex-4-ene-1,2-diol (3), and (1S,3R,3aR,6S,7S,9aR)-decahydro-1-(hydroxymethyl)-1,7-dimethyl-3a,7-methano-3aH-cyclopentacyclooctene (4) were isolated from the leaves of Acer truncatum, together with twelve known compounds. Their structures were elucidated on the basis of extensive spectroscopic techniques. The absolute configuration of compound 3 was established by the modified Mosher's method. All compounds were evaluated for antibacterial activities.

(+)-Myristinins A and D from Knema elegans, which inhibit DNA polymerase beta and cleave DNA

A survey of crude plant extracts for DNA polymerase beta inhibitors resulted in the identification of a methyl ethyl ketone extract prepared from Knema elegans that strongly inhibited the enzyme. Subsequent bioassay-guided fractionation of the extract, using an assay to monitor the activity of DNA polymerase beta, led to the isolation of two potent inhibitors, (+)-myristinins A (1) and D (2), which are known flavans having unusual structures. (+)-Myristinins A and D exhibited IC50 values of 12 and 4.3 microM, respectively, as inhibitors of DNA polymerase beta in the presence of bovine serum albumin (BSA), and 2.7 and 1.2 microM in the absence of BSA. As such, they are the most potent DNA polymerase beta inhibitors reported to date. Compounds 1 and 2 potentiated the cytotoxicity of bleomycin toward cultured P388D1 cells, reducing the number of viable cells by at least 30% when employed at 9 microM concentration for 6 h in the presence of an otherwise nontoxic concentration of bleomycin (75 nM). Principles 1 and 2 also induced strong Cu2+-dependent DNA strand scission in a DNA cleavage assay. Accordingly, 1 and 2 exhibit two activities, namely, DNA polymerase beta inhibition and DNA damage.

Distribution of flavonoids in the Myristicaceae

During the past two decades the study of the Myristicaceae species has increased, and many flavonoids of different types have been isolated. This review discusses the flavonoids presently known in the Myristicaceae.