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

Two new cassane diterpenoids, 14ß-hydroxycassa-11(12),13(15)-dien-12,16-olide (1) and 6'-acetoxypterolobirin B (3), together with a known analogue, identified as 12α,14ß-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,ß-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.

Synthesis of spirocyclic heterocycles from α,ß-unsaturated N-acyliminium ions.

The reactions of α,ß-unsaturated N-acyliminium ions, generated in situ from 4(S)-O-substitutedhydroxy-5-hydroxy-5-vinyl-N-alkylpyrrolidin-2-ones, with allylsilanes and indoles leading to the formation of spirocyclic heterocycles, are reported. Six single crystal X-ray structures and extensive 2D NMR experiments confirmed the structures and stereochemistries of these products. In addition, computational studies provided mechanistic insights and an understanding of the stereochemical outcomes of these reactions.

Polyoxygenated Cyclohexenes and Their Chlorinated Derivatives from the Leaves of Uvaria cherrevensis.

The chemical study of leaf extracts from Uvaria cherrevensis resulted in the identification of 11 new polyoxygenated cyclohexenes, cherrevenols A-K (1-11), and a new seco-cyclohexene derivative, cherrevenol L (12). Nine known compounds (13-21) were also isolated. Three of the isolated compounds are chlorinated polyoxygenated cyclohexenes. The structures of these compounds were determined using spectroscopic methods and, in some cases (compounds 2, 6, 8, and 10), single-crystal X-ray crystallographic structural analysis or chemical correlation (compounds 6 and 7). Compounds 6 and 7 were both isolated as scalemic mixtures (ee 23-24%).

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.

Synthesis of syn- and enantioenriched anti-ß-amino alcohols by highly diastereoselective borono-Mannich allylation reactions.

A highly diastereoselective method for the synthesis of syn-ß-amino alcohols and enantioenriched anti-ß-amino alcohols has been developed involving α-hydroxyl aldehydes and chiral α-phenylaminoxyaldehydes or α-benzoyloxyaldehydes, respectively in Petasis borono-Mannich allylation reactions. This study broadens the scope and utility of the Petasis reaction to include pinacol allylboronate and highlights its unique reactivity and stereochemical outcomes.

Nitric oxide production inhibitory activity of clerodane diterpenes from Monoon membranifolium.

A new clerodane diterpene, 2ß-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).

Unique polyacetylenic ester-neolignan derivatives from Mitrephora tomentosa and their antimalarial activities.

The phytochemical investigation of the methanol extracts of the leaves and twigs of Mitrephora tomentosa Hook. f. & Thomson resulted in the isolation and identification of undescribed polyacetylenic ester-neolignan derivatives, along with six known compounds. These six undescribed natural products were named as mitrephentosins A-F. The structures of these compounds were determined by spectroscopic techniques including UV, IR, NMR, and mass spectrometric analyses. The absolute configurations of mitrephentosins A-F were determined based on specific rotations values and ECD spectral data by comparisons made with the known parent neoligan compound mitredrusin. Mitrephentosins C, E, and F showed moderate antimalarial activities (IC50 values of 13.3-24.6 µM) against the Plasmodium falciparum strains TM4/8.2 and K1CB1 and were not toxic to Vero cells, while the other isolated compounds were not active against these P. falciparum strains.

A new xanthone and a biphenyl from the flower and twig extracts of Garcinia mckeaniana.

The phytochemical investigation of the flower and twig extracts of Garcinia mckeaniana yielded a new xanthone, mckeanianone F (1) and a new biphenyl, mckeaniabiphenyl (2) together with 15 known compounds. The isolated compounds were characterized using spectroscopic techniques and mass spectrometry. Some of the isolated compounds from the twigs exhibited antimalarial and cytotoxic activities.

(R)-3-(8'-Hydroxyfarnesyl)-indole and other chemical constituents from the flowers of Anomianthus dulcis and their antimalarial and cytotoxic activities.

A new farnesylindole, (R)-3-(8'-hydroxyfarnesyl)-indole (1), as a scalemic mixture (33% ee) along with nine known compounds (2-10), including one farnesylindole, three flavanones, three flavone derivatives and two chalcone derivatives were isolated from the methanolic crude extract of the flowers from Anomianthus dulcis. All compounds were purified by appropriate chromatographic techniques and their structures elucidated by spectroscopic methods. Compounds 1, 2 and 8 showed moderate antiplasmodial activities against TM4/8.Two and K1CB1 strains of which compound 2 displayed the best activity with IC50 values of 27.9 ± 2.57 and 21.4 ± 1.68 µM, respectively. In addition, compound 1 also presented modest cytotoxicity against a KB cell line with an IC50 value of 22.3 ± 0.39 µM. None of these compounds showed cytotoxicity against Vero cells.

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.

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.

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).

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.

Antibacterial and cytotoxic activities of phenolic constituents from the stem extracts of Spatholobus parviflorus.

A new 2-arylbenzofuran, spathobenzofuran (1), together with ten known compounds including a 2-arylbenzofuran, three pterocarpans and six isoflavones were isolated from the acetone crude extract of the stems of Spatholobus parviflorus. All compounds were characterised by spectroscopic methods. Compound 4 was active (MIC 8 µg/mL) against Gram-negative Pseudomonas aeruginosa TISTR 781 while compound 2 had modest activity against Gram-positive Staphylococcus aureus TISTR 1466 with a MIC value of 16 µg/mL. All isolated compounds showed no cytotoxicity against Vero and KB cells.

Four new C-benzyl flavonoids from the fruit of Uvaria cherrevensis.

The phytochemical investigation of the fruit extracts of Uvaria cherrevensis led to the isolation and characterization of four new C-benzyl flavonoids; cherrevenones A-D (1-4) together with 11 known compounds. The isolated compounds were characterized using spectroscopic techniques. Compounds 1, 3, 5 and 11 showed moderate inhibitory activities against the P. falciparum strains TM4/8.2 and K1CB1 with IC50 values ranging from 21.0 ±â€¯3.10 - 33.7 ±â€¯7.69 and 21.0 ±â€¯5.44 - 43.5 ±â€¯11.9 µM, respectively. Compounds 1, 2, 5, 10 and 11 exhibited strong cytotoxic activities against KB cells with IC50 values ranging from 0.60 ±â€¯0.17 - 4.91 ±â€¯2.69 µM which were similar to their cytotoxic activities found against Vero cells, except for compound 5, which was non-toxic to Vero cells.