Potent α-glucosidase inhibitory activity of compounds isolated from the leaf extracts of Uvaria hamiltonii

The phytochemical investigation of the leaf extracts of Uvaria hamiltonii (Annonaceae) led to the isolation and identification of ten compounds including a new seco-cyclohexene (1) together with nine known compounds (2-10). Their structures were elucidated by intensive analysis by spectroscopic methods and comparisons of their spectroscopic data with those of compounds reported in the literature. Compounds 2, 8, and 9 showed potent α-glucosidase inhibitory activity with the IC50 values ranging from 2.6-7.1 µM

Synthetic and spectroscopic studies on the structures of uniflorines A and B: structural revision to 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine alkaloids

The diastereoselective synthesis of the C-2 epimer and the C-1, C-2 di-epimers of the putative structure of the alkaloid uniflorine A has been achieved. The synthesis of the latter di-epimers employed a novel pyrrolo[1,2-c]oxazin-1-one precursor to allow for the reversal of π-facial diastereoselectivity in an osmium(VIII)-catalyzed syn-dihydroxylation (DH) reaction. The NMR spectral data of these epimeric compounds and that of related isomers did not match that of the natural product. From a comparison of the NMR data of uniflorines A and B with that of casuarine and the known synthetic 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine isomers we concluded unequivocally that uniflorine B is the known alkaloid casuarine. Although we cannot unequivocally prove the structure of uniflorine A, without access to the original material and data, the published data suggest that the natural product is also a 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine with the same relative C-7–C-7a–C-1–C-2–C-3 stereochemistry as casuarine. We thus suggest that uniflorine A is 6-epi-casuarine

Isolation of linobiflavonoid, a novel biflavonoid from Linostoma pauciflorum Griff

A novel biflavonoid, that we have named linobiflavonoid, and the known biscoumarin ether, daphnoretin, were isolated from the root extracts of Linostoma pauciflorum Griff. The structure of linobiflavonoid was determined from interpretation of its NMR spectroscopic data and from a comparison of this data with those of known biflavonoids and biflavones. The known flavones, 5,4\u27-dihydroxy- 7,3\u27,5\u27-trimethoxyflavone and 5,4\u27-dihydroxy-7-methoxyflavone along with stigmasterol were isolated from the vines of the same plant. 4\u27-Dihydroxy-7,3\u27-5\u27-trimethoxyflavone was active against Mycobacterium tuberculosis (MIC 3.13 mu M) and KB-oral cavity cancer (IC50 17.41 mu M). (C) 2011 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved

Gold- and Silver-Catalysed Cyclisation Reactions of β-Amino Allenes

Herein we report the formation of pyrrolines and tetrahydropyridines from the cyclisation reactions of β-amino allenes by both AuI and AgI catalysts in yields ranging from 5 to 70 %. AuI catalysts favour a 5-endo-dig cyclisation before rapid rearrangement to the 5-exo-dig product, while AgI favours a 6-endo-trig cyclisation. We also report the first known Ag2O catalysed cyclisation reaction of an allene which occurred in good yield (61 %)

Chemical constituents and antioxidant and biological activities of the essential oil from leaves of Solanum spirale

The essential oil of the leaves Solanium spirale Roxb. was isolated by hydrodistillation and analyzed for the first time using GC and GC-MS. Thirty-nine constituents were identified, constituting 73.36% of the total chromatographical oil components. (E)-Phytol (48.10%), n-hexadecanoic acid (7.34%), beta-selinene (3.67%), alpha-selinene (2.74%), octadecanoic acid (2.12%) and hexahydrofarnesyl acetone (2.00%) were the major components of this oil. The antioxidant activity of the essential oil was evaluated by using the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging assay. The oil exhibited week antioxidant activity with an IC50 of 41.89 mg/mL. The essential oil showed significant antibacterial activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus with MIC values of 43.0 microg/mL and 21.5 microg/mL, respectively. It also showed significant cytotoxicity against KB (oral cancer), MCF-7 (breast cancer) and NCI-H187 (small cell lung cancer) with the IC50 values of 26.42, 19.69, and 24.02 microg/mL, respectively

Free fatty acids from the crude hexane extract of the aerial parts of Heliotropium indicum Linn. Growing in Phitsanulok, Thailand

Sixteen free fatty acids from the crude hexane extract of the aerial parts of Heliotropium indicum Linn. growing in Phitsanulok, Thailand, have been identified after conversion to their methyl esters with boron trifluoride-methanol followed by quantification by GC-FID and identification by GC-MS analysis. They accounted for 95% of the chromatographable components, with 9,12-octadecadienoic acid, (39.7%), 9-octadecenoic acid (32.4%), hexadecanoic acid (14.2%) and octadecanoic acid (5.1%), as the major constituents. A small amount of 6,10,14-trimethyl-2-pentadecanone and 3,7,11,15-tetramethyl-2-hexadecen-1-ol as well as a homologous series of n-alkanes present at trace level and ranging from C25 to C31 was also found (see Table 1). The crude hexane extract has been shown to have modest antituberculosis activity (MIC of 100 mg/mL) against Mycobacterium tuberculosis H37Ra

Antimalarial, anticancer, antimicrobial activities and chemical constituents of essential oil from the aerial parts of Cyperus kyllingia Endl.

The chemical constituents of the essential oil from Cyperus kyllingia Endl. were analyzed by a GC, GC-MS. Twenty-three compounds were identified, accounting for 93.75% of the total oil that consisted mainly of oxygenated sesquiterpenes (53.52%), particularly sesquiterpene hydrocarbons (38.97%), and carboxylic acid (1.26%). The most representative compounds were α-cadinol (19.32%), caryophyllene oxide (12.17%), α-muurolol (11.58%), α-humulene (9.85%), and α-atlantone (6.07%). The oil showed significant activities against Plasmodium falcipalum (K1, multi drug resistant strain) and NCI-H187 (Small Cell Lung Cancer) with the IC50 values of 7.52 and 7.72 μg/mL, respectively. The oil exhibited highly active against Staphylococcus aureus ATCC25923 and moderately active against Escherichia coli ATCC25922, Pseudomonas aeruginosa ATCC27553, Aspergillus flavus and Candida albicans