Bioassay-Guided Isolation and Identification of Cytotoxic Compounds from Melaleuca quinquenervia Fruits

The fruit extract of Melaleuca quinquenervia yielded a total of 19 compounds, including two novel spiro-biflavonoid enantiomers (1a and 1b) and a chalcone derivative (3). Their structures were determined through spectroscopic analysis. The enantiomers of the racemic mixture of compound 1 were successfully resolved into (+)-1 and (-)-1 using chiral-phase HPLC. Single-crystal X-ray diffraction analysis was also used to confirm the structure of 1. The enantiomeric configurations of 1 and 2 were determined through a comparison of the calculated and experimental electronic circular dichroism spectra. Compounds 2 (melanervin), 14 (methyl betulinate), 15 (3-O-acetylbetulinic acid), and 16 (pyracrenic acid) were found to be highly cytotoxic, with compound 16 showing superior growth inhibition of nonsmall cell lung cancer cells (A549 cells) (IC50 2.8 ± 0.1 μM) compared to cisplatin (IC50 3.3 ± 0.0 μM), a positive control chemotherapeutic drug. Both compound 16 and cisplatin were significantly more cytotoxic toward A549 lung cancer cells compared to nontumorigenic Vero E6 cells.

Cassane diterpenoids with α-glucosidase inhibitory activity from the fruits of Pterolobium macropterum

Two new cassane diterpenoids, 14β-hydroxycassa-11(12),13(15)-dien-12,16-olide (1) and 6'-acetoxypterolobirin B (3), together with a known analogue, identified as 12α,14β-dihydroxycassa-13(15)-en-12,16-olide (2), were isolated from the fruits of Pterolobium macropterum. Compound 1 is a cassane diterpenoid with a Δ¹¹⁽¹²⁾ double bond conjugated with an α,β-butenolide-type, whereas compound 3 is a dimeric caged cassane diterpenoid with unique 6/6/6/6/6/5/6/6/6 nonacyclic ring system. The structures of 1 and 3 were characterized by extensive spectroscopic analysis combined with computational ECD analyses. The α-glucosidase inhibitory activity of isolated compounds was evaluated, and compounds 1 and 3 showed significant α-glucosidase inhibitory activity with IC₅₀ values of 66 and 44 μM.

Discovery of lead natural products for developing pan-SARS-CoV-2 therapeutics

The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains a global public health crisis. The reduced efficacy of therapeutic monoclonal antibodies against emerging SARS-CoV-2 variants of concern (VOCs), such as omicron BA.5 subvariants, has underlined the need to explore a novel spectrum of antivirals that are effective against existing and evolving SARS-CoV-2 VOCs. To address the need for novel therapeutic options, we applied cell-based high-content screening to a library of natural products (NPs) obtained from plants, fungi, bacteria, and marine sponges, which represent a considerable diversity of chemical scaffolds. The antiviral effect of 373 NPs was evaluated using the mNeonGreen (mNG) reporter SARS-CoV-2 virus in a lung epithelial cell line (Calu-3). The screening identified 26 NPs with half-maximal effective concentrations (EC50) below 50 μM against mNG-SARS-CoV-2; 16 of these had EC50 values below 10 μM and three NPs (holyrine A, alotaketal C, and bafilomycin D) had EC50 values in the nanomolar range. We demonstrated the pan-SARS-CoV-2 activity of these three lead antivirals against SARS-CoV-2 highly transmissible Omicron subvariants (BA.5, BA.2 and BA.1) and highly pathogenic Delta VOCs in human Calu-3 lung cells. Notably, holyrine A, alotaketal C, and bafilomycin D, are potent nanomolar inhibitors of SARS-CoV-2 Omicron subvariants BA.5 and BA.2. The pan-SARS-CoV-2 activity of alotaketal C [protein kinase C (PKC) activator] and bafilomycin D (V-ATPase inhibitor) suggest that these two NPs are acting as host-directed antivirals (HDAs). Future research should explore whether PKC regulation impacts human susceptibility to and the severity of SARS-CoV-2 infection, and it should confirm the important role of human V-ATPase in the VOC lifecycle. Interestingly, we observed a synergistic action of bafilomycin D and N-0385 (a highly potent inhibitor of human TMPRSS2 protease) against Omicron subvariant BA.2 in human Calu-3 lung cells, which suggests that these two highly potent HDAs are targeting two different mechanisms of SARS-CoV-2 entry. Overall, our study provides insight into the potential of NPs with highly diverse chemical structures as valuable inspirational starting points for developing pan-SARS-CoV-2 therapeutics and for unravelling potential host factors and pathways regulating SARS-CoV-2 VOC infection including emerging omicron BA.5 subvariants.

Rare prenylated isoflavonoids from the young twigs of Millettia extensa and their cytotoxic activities

Three new isoflavonoids, millexatins N-P (1-3), along with seven known compounds (6-10), were isolated from the acetone extract of the young twigs of Millettia extensa. The structures were characterized by NMR spectroscopic and mass spectrometric analyses. Millexatin N (1) is an unusual geminal diisoprenylated isoflavone with a modified ring A. Millexatin P (3) is an unusual isoflavone with a cyclohexyl substituent on ring B, which is extremely rare in nature. The isolated metabolites (1, 2, and 6-10) were evaluated for cytotoxicities against MDA-MB231, Huh-7, KKU-100 and normal human dermal fibroblast (NHDF) cell lines. Only compounds 1, 6 and 8 showed cytotoxicities against all cell lines with IC₅₀ values ranging from 13.9 to 30.9 μM.

Marginaols G-M, anti-inflammatory isopimarane diterpenoids, from the rhizomes of Kaempferia marginata

Marginaols G-M, a series of undescribed isopimarane diterpenoids, together with four known analogs were isolated from the rhizomes of Kaempferia marginata. The structures of these isolated compounds were characterized using high-resolution mass spectrometry and extensive 1D- and 2D-nuclear magnetic resonance (NMR) analyses. In addition, the absolute configurations of marginaol G and H were determined by X-ray crystallographic analysis and comparison with the literature values. When compared to the standard drug dexamethasone (IC₅₀ 4.7 μM), marginaol G, H, and 6β-acetoxysandaracopimaradien-1α,9α-diol had an intriguing anti-inflammatory effect on NO inhibition in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages, with IC₅₀ values ranging from 4.5 to 7.3 μM and being less cytotoxic to the cells. The anti-inflammatory action of these isopimarane diterpenoids from K. marginata supports the use of Thai traditional medicine for inflammation treatment.

Macluracochinones A-E, antimicrobial flavonoids from Maclura cochinchinensis (Lour.) Corner

The phytochemical investigation of the fruit and leaf extracts of Maclura cochinchinensis (Lour.) Corner (Moraceae) resulted in the isolation and identification of four undescribed isoflavones (macluracochinones A-D) and one undescribed flavone (macluracochinone E), together with 24 known compounds. The structures of the undescribed compounds were elucidated using nuclear magnetic resonance (NMR) and high-resolution electrospray ionization time-of-flight mass spectrometry (HRESITOFMS) experiments. Gancaonin M, lupiwighteone, lupalbigenin, warangalone, auriculatin, and millexatin F displayed good antibacterial activities against Gram-positive bacteria with MIC values in the range of 1-8 μg/mL. Lupalbigenin showed strong activities against methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus with the same MIC value of 1 μg/mL.

Daldiniaeschsone A, a Rare Tricyclic Polyketide Having a Chromone Unit Fused to a δ-Lactone and Its Symmetrical Biphenyl Dimer, Daldiniaeschsone B, from an Endophytic Fungus Daldinia eschscholtzii SDBR-CMUNKC745

Daldiniaeschsone A (1), a rare tricyclic polyketide having a chromone unit fused to a δ-lactone and its symmetrical 6,6'-biphenyl dimer, daldiniaeschsone B (2), together with three known compounds (3-5), were isolated from a plant-derived endophytic fungus, Daldinia eschscholtzii SDBR-CMUNKC745. Their structures were elucidated by extensive 1D and 2D NMR spectroscopic data and HRESIMS. All compounds showed α-glucosidase inhibitory activity with IC50 values ranging from 0.16-0.85 mM and compound 1 was the best α-glucosidase inhibitory activity (IC50 = 0.16 mM).

Nitric oxide production inhibitory activity of clerodane diterpenes from Monoon membranifolium

A new clerodane diterpene, 2β-methoxyhardwickiic acid (1), and four known compounds (2-5) were isolated from the twigs of Monoon membranifolium. The structure of the new compound was determined by extensive spectroscopic methods and ESITOFMS data. The absolute configuration of 1 was established by a comparison of its ECD spectrum and specific rotation with those of related previously reported compounds. All compounds were evaluated for their nitric oxide (NO) production inhibitory activities in RAW264.7 macrophage cells. Compounds 3 and 5 inhibited NO production with IC₅₀ values of 16.1 and 28.9 μM, respectively, which were better than that of standard compound, indomethacin (IC₅₀ = 32.2 μM).

Antidiabetic and antimicrobial flavonoids from the twigs and roots of Erythrina subumbrans (Hassk.) Merr

The phytochemical investigation of the twig and root extracts of Erythrina subumbrans (Hassk.) Merr. (Fabaceae) resulted in the isolation and identification of a new pterocarpan, erythrinocarpan (1), along with 27 known compounds (2-28). All isolated compounds were evaluated for their antidiabetic, antimicrobial, and anti-inflammatory properties. Compounds 3, 8, 9, and 22 had α-glucosidase inhibitory activity with IC50 values of 13.4 ± 0.05, 24.5 ± 0.13, 29.0 ± 0.05, and 12.8 ± 0.14 μM, respectively, while compound 2 inhibited α-amylase activity with an IC50 value of 67.6 ± 1.12 μM. Compounds 22 and 24 inhibited glycation activity with the IC50 values of 36.9 ± 0.62 and 40.5 ± 0.37 μM, respectively. From cell-based assays, compound 27 showed the highest ability to induce glucose consumption (IC50 29.1 ± 0.86 μM) and glucose uptake (2.8-fold), and to inhibit nitric oxide (NO) production (IC50 52.5 ± 0.56 μM) without cell toxicity. Furthermore, compound 9 showed antimicrobial activities against Gram-positive bacteria and fungi with MIC values ranging from 2-4 μg/mL.

Isopimarane Diterpenoids from the Rhizomes of Kaempferia marginata and Their Potential Anti-inflammatory Activities

Six new isopimarane diterpenes, marginaols A-F (1-6), along with eight known compounds (7-14), were isolated from the rhizomes of Kaempferia marginata. The structures and absolute configurations of 1-6 were established on the basis of spectroscopic methods and the experimental and calculated ECD data as well as comparison with the literature values. Most of the isolated compounds were tested for their nitric oxide (NO) inhibitory effects in lipopolysaccharide-activated RAW264.7 cells. Among them, marginaol B (2) was found to reduce NO levels in murine macrophage cells with an IC₅₀ value of 28.1 ± 1.7 μM.

Desmoschinensisflavones A and B, two rare flavones having a hybrid benzyl benzoate ester-flavone structural framework from Desmos chinensis Lour

Two rare flavones having a hybrid benzyl benzoate ester-flavone structural framework, desmoschinensisflavones A and B (1 and 2), together with 12 known compounds (3–14) were isolated from the fruit, leaf, and twig extracts of Desmos chinensis (red flower). The new structures were characterized by UV, IR, NMR, and HRESITOFMS data. Desmoschinensisflavones A and B have a distinctive skeleton of benzoate ester-flavones with a C-4′′ and C-6 and C-8 connection via a methylene group, respectively. Plausible biosynthesis pathways to compounds 1 and 2 are proposed based on an intermolecular nucleophilic 1,4-addition to ortho-quinone intermediates. Compounds 6–8 and 12 showed weakly antioxidant inhibition with IC₅₀ values in the range of 65.4–74.6 μM.

Two rare flavones having a hybrid benzyl benzoate ester-flavone structural framework, desmoschinensisflavones A and B (1 and 2), together with 12 known compounds (3–14) were isolated from Desmos chinensis (red flower).

Mallopenins A-E, Antibacterial Phenolic Derivatives from the Fruits of Mallotus philippensis

The chromatographic separation of the components of the acetone extract of Mallotus philippensis fruits yielded five new phenolic compounds including two chalcones, 1 and 3, a functionalized phloroglucinol, 2, two flavanones, 4 and 5, and six known compounds. The structures of 1-5 were confirmed by NMR and mass analyses. Racemic compounds 1 and 2 were separated by chiral-phase HPLC, and the absolute configuration of (+)-1 was confirmed by X-ray diffraction studies and ECD spectroscopic data. The configurations of the enantiomers of 2 were defined by comparison of its ECD data with those of (+)-1. Compounds 6 and 7 exhibited significant antibacterial activities, with MIC values ranging from 3.8 to 15.5 μM.

Antimalarial and cytotoxic activities of pregnene-type steroidal alkaloids from Holarrhena pubescens roots

The phytochemical investigation of an alkaloidal extract of Holarrhena pubescens roots led to the isolation and identification of a new pregnene-type alkaloid, mokluangin D (1), together with nine known steroidal alkaloids (2-10). The structure of the new metabolite was determined on the basis of spectroscopic analyses including 1D- and 2D-NMR spectroscopy and mass spectrometry. Compounds 3 and 4 showed potent antimalarial activity against Plasmodium falciparum K1 stain with IC₅₀ values of 1.2 and 2.0 μM, respectively, and showed weak cytotoxic activity against the NCI-H187 cell line with IC₅₀ values of 27.7 and 30.6 μM, respectively. The substituent groups at C-3 and the carbonyl group at C-18 are important for the activity against the P. falciparum K1 stain.

Antioxidant, Cytotoxic and α-Glucosidase Inhibitory Activities of Compounds isolated from the Twig Extracts of Maclura fruticosa

The first phytochemical investigation of the twig extracts of Maclura fruticosa led to the isolation and identification of a new xanthone, maclurafruticosone (1), together with 14 known compounds (2–15). All compounds were elucidated using spectroscopic methods as well as through comparisons made with data reported in the literature. Some isolated compounds were evaluated for their antioxidant, α-glucosidase inhibitory and cytotoxic activities. Compound 4, 6 and 7 showed significant antioxidant activity against DPPH radicals with IC50 values ranging from 7.45–16.12 μM. Compound 4 also exhibited potent activity against ABTS•+ scavenging activity with an IC50 value of 0.55 ± 0.01 μM which was better than positive control (ascorbic acid, IC50 2.35 ± 0.17 μM). Compound 12 showed significant α-glucosidase inhibitory activity with an IC50 value of 0.02 ± 0.37 mM. Compounds 5, 6 and 12 showed weak cytotoxic activities against a colon cancer cell line with IC50 values ranging from 22.35–47.62 μM.

New Benzophenones and Xanthones from Cratoxylum sumatranum ssp. neriifolium and Their Antibacterial and Antioxidant Activities

Two new benzophenones (1 and 2) and four new xanthones (4-6 and 17) together with 24 known compounds (3, 7-16, and 18-30) were isolated from the roots and twigs of Cratoxylum sumatranum ssp. neriifolium. Their structures were elucidated by spectroscopic methods. Compounds 5 and 26 showed antibacterial activity against Micrococcus luteus, Bacillus cereus, and Staphylococcus epidermis with minimum inhibitory concentrations ranging from 4 to 8 μg/mL, whereas compounds 7, 20, and 26 displayed selective antibacterial activities against Staphylococcus aureus (8 μg/mL), Salmonella typhimurium (4 μg/mL), and Pseudomonas aeruginosa (4 μg/mL), respectively. The radical scavenging effects of some isolated compounds were investigated. Compounds 11 and 21 exhibited potent activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) with IC₅₀ values of 7.0 ± 1.0 and 6.0 ± 0.2 μM, respectively.

Antimalarial Oxoprotoberberine Alkaloids from the Leaves of Miliusa cuneata

Five new oxoprotoberberine alkaloids, miliusacunines A-E (1-5), along with nine known compounds, 6-14, were isolated from an acetone extract of the leaves and twigs of Miliusa cuneata. Their structures were elucidated by spectroscopic analysis. All isolated compounds were evaluated for their cytotoxicities against the KB and Vero cell lines and for antimalarial activities against the Plasmodium falciparum strains TM4 and K1 (a sensitive and a multi-drug-resistant strain, respectively). Compound 1 showed in vitro antimalarial activity against the TM4 strain, with an IC50 value of 19.3 ± 3.4 μM, and compound 2 demonstrated significant activity against the K1 strain, with an IC50 value of 10.8 ± 4.1 μM. Both compounds showed no discernible cytotoxicity to the Vero cell line at the concentration levels evaluated.

Acetylcholinesterase inhibitory activity and molecular docking study of steroidal alkaloids from Holarrhena pubescens barks

An alkaloidal extract of the bark of Holarrhena pubescens showed several inhibition zones of acetylcholinesterase (AChE) inhibitor, using a bioautographic assay. Activity-guided fractionation afforded three new steroidal alkaloids, mokluangins A-C (1-3), together with three known compounds, antidysentericine (4), holaphyllamine (5), methylholaphyllamine (6). All structures were elucidated by analysis of NMR and MS spectroscopic data. Compound 2 showed moderate antibacterial activity against Bacillus subtilis and Escherichia coli with the MIC value of 16 μg/mL, while compound 3 exhibited moderate selective activity against E. coli with the MIC value of 16 μg/mL. In addition, compounds 1-4 also showed strong AChE inhibiting activity with IC50 values ranging from 1.44 to 23.22 μM. Molecular docking calculations were also performed and the results demonstrated that all compounds can bind at the aromatic gorge of AChE with estimated binding free energies correlated well with the in vitro inhibitory profiles. Hydrophobic and hydrogen bonding interactions contribute mainly to the binding of the alkaloids where the substituents at C-3 serving as key functional groups for the AChE inhibition. Our results will allow the development of new AChE-inhibitors based on steroidal alkaloid skeleton bearing the cyclic amide moiety.

Xanthones from Garcinia Propinqua Roots

Phytochemical investigation of Garcinia propinqua roots led to the isolation and identification of a new xanthone, doitunggarcinone D (1), together with 15 known compounds (2–16). Their structures were elucidated by intensive analysis of spectroscopic data. Compounds 3, 6, 7, 14, 15 and 16 exhibited strong antibacterial activity against Bacillus subtilis TISTR 088 with MIC values in the range of 1–4 μg/mL. Compounds 3, 7, 10 and 14 also showed good antibacterial activity against B. cereus TISTR 688 with MIC values ranging from 4–8 μg/mL.

A New Cytotoxic Clerodane Diterpene from Casearia Graveolens Twigs

The first phytochemical investigation of Casearia graveolens twigs led to the isolation and identification of a new clerodane diterpene, caseariagraveolin (1), together with six known compounds (2–7). Their structures were elucidated by intensive analysis of their spectroscopic data. Compound 1 showed strong cytotoxicity against oral cavity and breast cancer cell lines with IC50 values of 2.48 and 6.63 μM, respectively.

A New Cytotoxic Clerodane Diterpene from Casearia graveolens Twigs

The first phytochemical investigation of Casearia graveolens twigs led to the isolation and identification of a new clerodane diterpene, caseariagraveolin (1), together with six known compounds (2-7). Their structures were elucidated by intensive analysis of their spectroscopic data. Compound 1 showed strong cytotoxicity against oral cavity and breast cancer cell lines with IC₅₀ values of 2.48 and 6.63 µM, respectively.

Xanthones from Garcinia propinqua Roots

Phytochemical investigation of Garcinia propinqua roots led to the isolation and identification of a new xanthone, doitunggarcinone D (1), together with 15 known compounds (2-16). Their structures were elucidated by intensive analysis of spectroscopic data. Compounds 3, 6, 7, 14, 15 and 16 exhibited strong antibacterial activity against Bacillus subtilis TISTR 088 with MIC values in the range of 1-4 µg/mL. Compounds 3, 7, 10 and 14 also showed good antibacterial activity against B. cereus TISTR 688 with MIC values ranging from 4-8 µg/mL.

Antibacterial compounds from the roots of Cratoxylumformosum spp. pruniflorum

Phytochemical investigation of the roots of Cratoxylum formosum spp. pruniflolnnm led to the isolation and identification of a new xanthone, namely cratopruniforone (1), together with 13 known compounds (2-14). Some of these more abundant compounds were evaluated for their antibacterial activities.

Monoterpene Indole Alkaloids from the Twigs of Kopsia arborea

The phytochemistry of Kopsia arborea Blume has received considerable attention, which has resulted in the isolation of a number of new unusual indole alkaloids with intriguing structures. In this study, a new eburnane-type alkaloid, phutdonginin (1), together with eight known alkaloids: 19-OH-(-)-eburnamonine (2), melodinine E (3), kopsinine (4), kopsilongine (5), kopsamine (6), (-)-methylenedioxy-11,12-kopsinaline (7), decarbomethoxykopsiline (8), and vincadifformine (9), were isolated from the twigs of K. arborea. Their structures were characterized extensively by 1D and 2D NMR spectroscopy and HR-ESI-MS. All compounds were submitted to TLC screening for acetylcholinesterase inhibitory activities. Only kopsamine and decarbomethoxykopsiline showed AChE inhibition with MIR values of 12.5 and 6.25 μg, respectively, compared with galanthamine (positive control, 0.004 μg). In addition, compounds 1 and 2 inhibited moderate antibacterial activity against E. coli TISTR 780 with the MIC value of 32 μg/mL.

Monoterpene indole alkaloids from the twigs of Kopsia arborea

The phytochemistry of Kopsia arborea Blume has received considerable attention, which has resulted in the isolation of a number of new unusual indole alkaloids with intriguing structures. In this study, a new eburnane-type alkaloid, phutdonginin (1), together with eight known alkaloids: 19-OH-(-)- eburnamonine (2), melodinine E (3), kopsinine (4), kopsilongine (5), kopsamine (6), (-)-methylenedioxy-1 1,12-kopsinaline (7), decarbomethoxykopsiline (8), and vincadifformine (9), were isolated from the twigs of K. arborea. Their structures were characterized extensively by 1D and 2D NMR spectroscopy and HR-ESI-MS. All compounds were submitted to TLC screening for acetylcholinesterase inhibitory activities. Only kopsamine and decarbomethoxykopsiline showed AChE inhibition with MIR values of 12.5 and 6.25 μg, respectively, compared with galanthamine (positive control, 0.004 μg). In addition, compounds 1 and 2 inhibited moderate antibacterial activity against E. coli TISTR 780 with the MIC value of 32 .g/mL.

Antibacterial Compounds from the Roots of Cratoxylum formosum spp. pruniflorum

Phytochemical investigation of the roots of Cratoxylum formosum spp. pruniflorum led to the isolation and identification of a new xanthone, namely cratopruniforone (1), together with 13 known compounds (2–14). Some of these more abundant compounds were evaluated for their antibacterial activities.

Alstoniaphyllines A-C, unusual nitrogenous derivatives from the bark of Alstonia macrophylla

Chemical investigation of an alkaloidal extract of Alstonia macrophylla bark led to the isolation and identification of two new nitrogenous derivatives, alstoniaphyllines A (1) and B (2), a new indole alkaloid, alstoniaphylline C (4), and eight known alkaloids (3, 5-11). Alstonisine (9) exhibited antiplasmodial activity against Plasmodium falciparum, with an IC50 of 7.6 μM.

Clausenawallines G-K, carbazole alkaloids from Clausena wallichii twigs

Five carbazole alkaloids, clausenawallines G-K (1-5), along with 12 known alkaloids (6-17) were isolated from the twigs of Clausena wallichii. Their structures were established using spectroscopic methods and the antibacterial activity of compounds 1-5 was evaluated.

Rearranged benzophenones and prenylated xanthones from Garcinia propinqua twigs

The first phytochemical investigation of Garcinia propinqua has led to the isolation and identification of three new compounds, including two rearranged benzophenones, doitunggarcinones A (1) and B (2), and a xanthone, doitunggarcinone C (3), together with seven known compounds (4-10). The structures of 1-3 were elucidated on the basis of spectroscopic methods, including UV, IR, NMR, and MS. The antibacterial activity of the 10 isolates was evaluated against Escherichia coli TISTR 780, Salmonella typhimurium TISTR 292, Staphylococcus aureus TISTR 1466, and methicillin-resistant Staphylococcus aureus (MRSA) SK1.

Bioactive carbazole alkaloids from Clausena wallichii roots

Four new carbazole alkaloids, clausenawallines C-F (1-4), along with 18 known compounds (5-22) were isolated from the roots of Clausena wallichii. Compounds 3, 9, and 22 exhibited significant antibacterial activity against methicillin-resistant Staphylococcus aureus SK1 (MRSA SK1) and Staph. aureus TISTR 1466 with MIC values in the range 4-16 μg/mL, whereas compound 4 showed the highest cytotoxicity against oral cavity cancer (KB) and small-cell lung cancer (NCI-H187) with IC(50) values of 10.2 and 4.5 μM, respectively.

Suppression of cyclooxygenase-2 and inducible nitric oxide synthase expression by epimuqubilin A via IKK/IκB/NF-κB pathways in lipopolysaccharide-stimulated RAW 264.7 cells

Lipopolysaccharide (LPS)-stimulated RAW 264.7 cells are commonly used as a model for assessing the anti-inflammatory or chemopreventive potential of test compounds. Epimuqubilin A, a norsesterterpene peroxide isolated from marine sponge Latrunculia sp., inhibits nitric oxide production in LPS-stimulated RAW 264.7 cells (IC(50) = 7.6 µM). At both the mRNA and protein levels, cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) are suppressed in a dose-dependent manner. Mitogen-activated protein kinases (MAPKs), one major upstream signaling pathway involved in the transcription of both COX-2 and iNOS, were not affected by treatment of epimuqubilin A. However, the compound blocked the phosphorylation of inhibitor κB (IκB) kinase (IKKβ), resulting in the stabilization of IκBα, and inhibition of NF-κB p65 nuclear translocation and DNA binding. Levels of phosphorylated IKKα were not affected. This is an unique mechanistic relationship that suggests epimuqubilin A warrants further exploration as a potential therapeutic agent.

Inhibition of lipopolysaccharide-induced cyclooxygenase-2 and inducible nitric oxide synthase expression by 4-[(2'-O-acetyl-α-L-rhamnosyloxy)benzyl]isothiocyanate from Moringa oleifera

Moringa oleifera Lamarck is commonly consumed for nutritional or medicinal properties. We recently reported the isolation and structure elucidation of novel bioactive phenolic glycosides, including 4-[(2'-O-acetyl-α-L-rhamnosyloxy)benzyl]isothiocyanate (RBITC), which was found to suppress inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production in lipopolysaccharide-stimulated RAW 264.7 mouse macrophage cells. Inhibitors of proteins such as cyclooxygenase-2 (COX-2) and iNOS are potential antiinflammatory and cancer chemopreventive agents. The inhibitory activity of RBITC on NO production (IC(50) = 0.96 ± 0.23 μM) was greater than that mediated by other well-known isothiocyanates such as sulforaphane (IC(50) = 2.86 ± 0.39 μM) and benzyl isothiocyanate (IC(50) = 2.08 ± 0.28 μM). RBITC inhibited expression of COX-2 and iNOS at both the protein and mRNA levels. Major upstream signaling pathways involved mitogen-activated protein kinases and nuclear factor-κB (NF-κB). RBITC inhibited phosphorylation of extracellular signal-regulated kinase and stress-activated protein kinase, as well as ubiquitin-dependent degradation of inhibitor κBα (IκBα). In accordance with IκBα degradation, nuclear accumulation of NF-κB and subsequent binding to NF-κB cis-acting element was attenuated by treatment with RBITC. These data suggest RBITC should be included in the dietary armamentarium of isothiocyanates potentially capable of mediating antiinflammatory or cancer chemopreventive activity.

Chemical constituents from the roots of Feroniella lucida

A new furanocoumarin named lucidafuranocoumarin A (7) together with 13 known coumarins (1-6, 8-14) and four known alkaloids (15-18) was isolated from the roots of Feroniella lucida. Their structures were elucidated on the basis of spectroscopic analysis. Some of the isolates were evaluated for their biological activities, and compound 18 showed strong cytotoxicity against KB (IC(50) = 0.637 μg/ml) and NCI-H187 (IC(50) = 0.094 μg/ml) human cancer cell lines, antimalarial activity against Plasmodium falciparum (IC(50) = 0.336 μg/ml), and antituberculosis activity against Mycobacterium tuberculosis (MIC = 6.25 μg/ml).

Anti-proliferative and anti-invasive properties of a purified fraction from Streptomyces sp. H7372

Secondary metabolites from actinomycetes especially the genus Streptomyces may be one of the most important sources for novel anticancer agents. A purified fraction from a novel actinomycete strain, Streptomyces sp. H7372, was elucidated in breast cancer cells. We have isolated three purified fractions from a novel strain, Streptomyces sp. H7372. One of the fractions, designated as 31-2, exhibited the strongest growth-inhibitory effect and thereby was selected for further studies. 31-2 exerted a growth-inhibitory effect on a panel of 15 human cancer and 2 non-malignant cell lines. In MCF-7 and MDA-MB-231 breast cancer cells, 31-2 induced a cytostatic (anti-proliferative) effect without causing cytotoxicity (cell death). Our data suggest that the cytostasis resulted from cell cycle arrest at the G1 phase in MCF-7 cells and at the S phase in MDA-MB-231 cells. Western blot analysis demonstrated a modulation of phosphorylation of the Rb and CDC2 proteins and of CDK4, cyclin D1 and cyclin D3 in the 31-2-treated breast cancer cell lines. The protein levels of CDK2, CDK6, and PCNA were not affected by 31-2 treatment. 31-2 also exhibited an anti-invasive effect in MDA-MB-231 cells. However, this effect is not attributed to the modulation of proteolytic activity in MDA-MB-231 cells as the enzymatic degradation of type IV collagen was not affected by 31-2. The 31-2 is a potent cytostatic and anti-invasive agent and modulates the cell cycle pathway. Together, these results will have important implications in searching for novel approaches to treat cancer.

Anti-inflammatory principles of Suregada multiflora against nitric oxide and prostaglandin E2 releases

AIM OF THE STUDY

The stem bark of Suregada multiflora and the isolated compounds were carried out to investigate for anti-inflammatory activity.

MATERIALS AND METHODS

The stem bark of Suregada multiflora and its isolated compounds were tested for their anti-inflammatory effects against lipopolysaccharide (LPS)-induced nitric oxide (NO) and prostraglandin E(2) (PGE(2)) releases in RAW264.7 cells as well as the anti-inflammatory mechanism on mRNA expression of the active compound (5, helioscopinolide A).

RESULTS

The extract of Suregada multiflora possessed potent NO inhibitory effect with an IC(50) value of 8.6 μg/ml. Among the isolated compounds, helioscopinolide A (5) exhibited the highest activity against NO release with an IC(50) value of 9.1 μM, followed by helioscopinolide C (6) and suremulol D (2) with IC(50) values of 24.5 and 29.3 μM, respectively. The IC(50) value of 5 against PGE(2) production was found to be 46.3 μM. The mechanism in transcriptional level of compound 5 was found to inhibit iNOS and COX-2 mRNA expressions in dose-dependent manners.

CONCLUSIONS

The present study may support the traditional use of Suregada multiflora stem bark for treatment of inflammatory-related diseases.

Coumabiocins A-F, aminocoumarins from an organic extract of Streptomyces sp. L-4-4

Bioassay-directed fractionation of the butanol extract of Streptomyces sp. L-4-4, using the hyphae formation inhibition assay of a prokaryotic whole cell, led to the isolation of six new aminocoumarins, coumabiocins A-F (1-6), along with two known compounds, novobiocin (7) and isonovobiocin (8). Coumabiocins A-E (1-5) contain three structural elements, a central 3-amino-7-hydroxycoumarin that is linked at the 3-amino group to a prenylated 4-hydroxybenzoic acid moiety and at the 7-position to an l-noviosyl sugar, while coumabiocin F (6) lacks the sugar moiety. Their structures were elucidated by spectroscopic methods including 1D- and 2D-NMR techniques and mass spectrometric analyses. Coumabiocins A-E (1-5) exhibited significant inhibitory activity against Streptomyces 85E and gave a 10-15 mm clear zone of inhibition at 20 microg/disk and a 10 mm bald and a 10 mm clear zone of inhibition at 5 and 10 microg/disk, respectively, whereas coumabiocin F (6) was inactive.

Potential anti-inflammatory phenolic glycosides from the medicinal plant Moringa oleifera fruits

Bioassay-guided isolation and purification of the ethyl acetate extract of Moringa oleifera fruits yielded three new phenolic glycosides; 4-[(2'-O-acetyl-alpha-l-rhamnosyloxy) benzyl]isothiocyanate (1), 4-[(3'-O-acetyl-alpha-l-rhamnosyloxy)benzyl]isothiocyanate (2), and S-methyl-N-{4-[(alpha-l-rhamnosyloxy)benzyl]}thiocarbamate (3), together with five known phenolic glycosides (4-8). The structures of the new metabolites were determined on the basis of spectroscopic analyses including 1D- and 2D-NMR and mass spectrometry. The anti-inflammatory activity of isolated compounds was investigated with the lipopolysaccharide (LPS)-induced murine macrophage RAW 264.7 cell line. It was found that 4-[(2'-O-acetyl-alpha-l-rhamnosyloxy)benzyl]isothiocyanate (1) possessed potent NO-inhibitory activity with an IC(50) value of 1.67 microM, followed by 2 (IC(50)=2.66 microM), 4 (IC(50)=2.71 microM), and 5 (IC(50)=14.4 microM), respectively. Western blots demonstrated these compounds reduced LPS-mediated iNOS expression. In the concentration range of the IC(50) values, no significant cytotoxicity was noted. Structure-activity relationships following NO-release indicated: (1) the isothiocyanate group was essential for activity, (2) acetylation of the isothiocyanate derivatives at C-2' or at C-3' of rhamnose led to higher activity, (3) un-acetylated isothiocyanate derivatives displayed eight times less activity than the acetylated derivatives, and (4) acetylation of the thiocarbamate derivatives enhanced activity. These data indicate compounds 1, 2, 4 and 5 are responsible for the reported NO-inhibitory effect of Moringa oleifera fruits, and further studies are warranted.

Inhibition of nitric oxide (NO) production in lipopolysaccharide (LPS)-activated murine macrophage RAW 264.7 cells by the norsesterterpene peroxide, epimuqubilin A

Seven norsesterterpene peroxides: epimuqubilin A (1), muqubilone B (2), unnamed cyclic peroxide ester (3), epimuqubilin B (4), sigmosceptrellin A methyl ester (5), sigmosceptrellin A (6), and sigmosceptrellin B methyl ester (7), isolated from the marine sponge Latrunculia sp., were examined with regard to their effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated murine macrophage RAW 264.7 cells. The results indicated epimuqubilin A (1) possessed potent NO inhibitory activity against lipopolysaccharide (LPS)-induced nitric oxide release with an IC(50) value of 7.4 microM, a level three times greater than the positive control, L-N(G)-monomethyl arginine citrate, followed by 6 (sigmosceptrellin A, IC(50) = 9.9 microM), whereas other compounds exhibited only modest activity (Table 1). These compounds did not show appreciable cytotoxicity at their IC(50) values for NO-inhibitory activity. The structure-activity upon NO inhibition could be summarized as follows: (1) a monocyclic carbon skeleton framework was essential for activity, (2) free acids gave higher activity, (3) the orientation of H3-22 with an equatorial position increased activity, and (4) a bicyclic structure reduced activity. This is the first report of a norsesterterpene peroxide with NO-inhibitory activity. In addition, compounds 1-7 were also evaluated for their inhibitory activities in the yeast glycogen synthase kinase-3beta assay. In summary, several norsesterterpene peroxides showed novel biological activities of inhibition in NO production, suggesting that these might provide leads for anti-inflammatory or cancer chemopreventive agents.

Candenatenins A-F, phenolic compounds from the heartwood of Dalbergia candenatensis

Chemical investigation of the CH2Cl2 extract of the heartwood of Dalbergia candenatensis affored six new phenolic compounds, designated candenatenins A-F (1-6), as well as four known compounds, (2R,3R)-3,5-dihydroxy-7-methoxyflavanone (7), 4-hydroxy-3-methoxy-8,9-methylenedioxypterocarpan (8), nutiducol (9), and sophoraflavanone A (10). The structures of the new compounds were determined by 1D- and 2D-NMR spectroscopic studies as well as by MS analysis. The cytotoxic activities of the isolated compounds are also reported.

Yeast glycogen synthase kinase-3beta pathway inhibitors from an organic extract of Streptomyces sp

Investigation of a microbial fermentation organic extract of Streptomyces sp. H7667 led to the isolation of three new imides, 3-[(5E)-5-methyl-4-oxo-2-hydroxy-5-octenyl]glutarimide (1), 2-amino-N-2'-(phenylacetyl)propanimide (5), and 2-amino-N-(2'-(cyclohex-2''-enyl)acetyl)acetimide (6), and one new isoflavonoid glycoside, 6-O-methyl-7-O-alpha-rhamnopyranosyldaidzein (7), along with four known compounds. Their structures were elucidated by HRESIMS, 1H and 13C NMR, COSY, HMQC, HMBC, and NOESY spectra. Compounds 1-8 were evaluated for their inhibitory activities in the yeast glycogen synthase kinase-3beta assay.

Anti-allergic activity of principles from the roots and heartwood of Caesalpinia sappan on antigen-induced beta-hexosaminidase release

The dichloromethane extract of the roots and heartwood of Caesalpinia sappan exhibited potent inhibitory activity against beta-hexosaminidase release as marker of degranulation in rat basophilic leukemic (RBL-2H3) cells, with inhibition of 98.7% and 87.5% at concentration of 100 microg/ml, respectively. These extracts were further separated by chromatographic techniques to give two chalcones and seven homoisoflavones. Among the compounds tested, sappanchalcone (2) possessed the most potent effect against allergic reaction in RBL-2H3 cells with an inhibitory concentration (IC50) value of 7.6 microM, followed by 3-deoxysappanchalcone (1, IC50 = 15.3 microM), whereas other compounds showed moderate and mild effects. The results suggested the following structural requirements of chalcones (1 and 2) and homoisoflavones (3-9) for anti-allergic activity: (i) chalcone exhibited higher activity than homoisoflavone (ii) vicinal hydroxylation at B-ring of chalcone conferred higher activity than one hydroxylation; and (iii) for homoisoflavone, the hydroxyl groups at C-3 and C-4 positions decreased the activity. This is the first report of C. sappan for anti-allergic activity.

Nitric oxide inhibitory principles from Derris trifoliata stems

Nine rotenoids were isolated from the hexane and dichloromethane extracts of Derris trifoliata stems and were tested for nitric oxide (NO) inhibitory activity using RAW264.7 cells. The result indicated that 12a-hydroxyrotenone (7) possessed very potent NO inhibitory activity with an IC(50) value of 0.002 microM, followed by 1 (deguelin, IC(50)=0.008 microM), 9 (12a-hydroxyelliptone, IC(50)=0.010 microM) and 2 (alpha-toxicarol, IC(50)=0.013 microM), respectively. In addition, the DPPH scavenging activity of rotenoids was also investigated. It was found that 6a,12a-dehydrodeguelin (5) possessed the highest activity against DPPH with an IC(50) value of 7.4 microM, followed by deguelin (1, IC(50)=27.4 microM). All compounds did not show any cytotoxicity at their IC(50) values for NO inhibitory activity. Structure-activity relationships (SARs) of these rotenoids against NO release are as follows: (1) hydroxylation at C12a dramatically increased activity, (2) prenylation at furan ring increased activity markedly and (3) hydrogenation of a double bond at C6a-C12a conferred higher activity. For the DPPH radical scavenging effect, it was found that (1) introduction of a double bond at C6a-C12a increased activity and (2) hydroxylation of C11 at the D-ring decreased activity. As regards active compounds of Derris trifoliata stems, the isolated compounds are responsible for the NO inhibitory effect, especially 7, 1, 9 and 2, whereas 5 and 1 are those for the DPPH scavenging activity.

Phanginin A-K, diterpenoids from the seeds of Caesalpinia sappan Linn

The first chemical study on the seeds of Caesalpinia sappan Linn. led to isolation of 11 cassane-type diterpenes, named phanginin A-K (1-11). The skeleton present in compounds 1-8 is rather unusual, consisting of a cassane-type diterpene with an ether bridge between C-19/C-20 in compounds 1-6 and C-11/C-20 in compounds 7 and 8. Their structures were elucidated on the basis of spectroscopic techniques. In addition, the X-ray structure of phanginin A (1) is reported. Only phanginin I (9) exhibited cytotoxic effect against KB cell line with IC50 value of 4.4 microg/ml.