6-Hydroxy-5,6-seco-stemocurtisine: a novel seco-stemocurtisine-type alkaloid

A novel seco-stemocurtisine-type alkaloid, 6-hydroxy-5,6-seco-stemocurtisine was isolated from the aerial parts of Stemona curtisii (Stemonaceae) collected from Trang Province in Thailand. The unprecedented 5,6-seco-pyrido[1,2-a] azepine structure was elucidated by 2D NMR analysis and a single crystal X-ray crystallographic analysis. (C) 2013 Phytochemical Society of Europe

PAW - the Protein Analysis Workshop for 2D nuclear magnetic resonance spectroscopy : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physics at Massey University, New Zealand

An X Window-based software package for SGI workstations has been developed to process and assign NMR spectra. Special consideration has been given to the assignment of two-dimensional 1H NMR spectra of proteins. The program combines features from the packages PROSPA [Eccles 1995], EASY [Eccles 1991] and FELIX [Biosym 1995] as well as having its own capabilities. It allows simultaneous display of multiple toolboxes and spectra, which can be flexibly manipulated by mouse operations, command entries, and user-editable macros. NMR spectra can be processed either interactively or with macros containing commands with parameters. A unique filter that combines the exponential and sine-bell functions has been frequently used. A water suppression technique based on fitting averaged time-domain data, as well as an efficient algorithm for calculating fast Fourier transform and Hilbert transform [Eccles 1995] are discussed and implemented. NMR spectral assignment is done interactively in three steps: peak picking, spin-system identification, and sequence-specific assignment. The process utilises three peak lists: a raw-peak list that contains records of all possible peaks in a NOESY spectrum, a diagonal peak list that contains records of peaks that define a curve about which the spectrum is symmetric, and a cross-peak list that contains records of peaks that are assigned. Details of the peak-picking methods are discussed. By reference to a list of diagonal peaks, a common calibration problem caused by Bloch-Siegert shifts [Bloch and Siegert 1940, Ernst 1987] has been minimised. Automatically produced NOE summaries allow a quick identification of peaks that are unassigned or incorrectly assigned. The peak position and integration parameters can be calculated through non-linear curve fitting with Gaussians. NMR data processing and spectral assignment using the package has been completed for Caerin 4.1, a 23-residue protein. Linear-prediction has been applied to increase the spectral resolution. Detailed results for this protein are presented. The NOE summary of the sequential assignments indicates a well-defined secondary structure that is different from Caerin 1.1 [Wong 1996, 1997]

Alkaloids from the roots and leaves of Stichoneuron halabalensis and their acetylcholinesterase inhibitory activities

A study of the hitherto unreported Stichoneuron halabalensis Inthachub led to the characterization of the known compounds (+)-α-tocopherol and (R)-(+)- goniothalamin; four known Stemona alkaloids, bisdehydoxystemoninine A (1), stemoninine (2), sessilistemonamine C (3) and sessilistemonamine A (4); and three new alkaloids, stichoneurine C (5), D (6) and E (7). The structures of these compounds were determined on the basis of their spectroscopic data. Alkaloid 7 showed significant inhibitory activity against electric eel acetylcholinesterase (AChE) (IC50 5.90+0.084 μM), while goniothalamin and compounds 1 and 2 showed significant inhibitory activities against human AChE (IC50 7.24+0.52, 5.52+0.13 and 3.74+0.09 μM, respectively)

Isolation of tuberospironine A, a novel croomine derivative from Stemona tuberosa Lour.

A novel croomine derivative, tuberospironine A (3-epi-tuberospironine) was isolated from the root extracts of Stemona tuberosa Lour. found growing on Seram Island, Moluccas Province, Indonesia. The structure of this novel alkaloid, with unprecedented configuration at C-3 for a croomine derivative, was determined from interpretation of its NMR spectroscopic data

Alkaloids from the roots of stichoneuron caudatum and their acetylcholinesterase inhibitory activities

Four new stichoneurine-type alkaloids, stichoneurines F and G (1-2) and sessilistemonamines E and F (3-4), have been isolated from the root extracts of Stichoneuron caudatum. The structures and relative configurations of these alkaloids have been determined by spectroscopic methods and molecular modeling experiments. Compounds 1-4 were tested for their acetylcholinesterase (AChE) inhibitory activities against human AChE. Compound 3 showed significant inhibitory activity with an IC50 value of 9.1 ± 0.15 μM

Semisynthesis and acetylcholinesterase inhibitory activity of stemofoline alkaloids and analogues

Semisynthesis of the known Stemona alkaloids oxystemofoline (7) and methoxystemofoline (8) has been achieved starting from (11Z)-1′,2′-didehydrostemofoline (6), which confirmed their structures and absolute configurations. The synthesis of (1′R)-hydroxystemofoline (9) helped establish this compound as a natural product from Stemona aphylla. (1′S)- Hydroxystemofoline (10) and a number of related analogues were also prepared. In a TLC bioautographic assay, 9 was found to be the most active acetylcholinesterase inhibitor, but it was not as active as galanthamine

Phytochemical Studies on Stemona aphylla: Isolation of a New Stemofoline Alkaloid and Six New Stemofurans

A new stemofoline alkaloid, (2′S)-hydroxy-(11S,12R)-dihydrostemofoline (3), new stemofurans M-R (8-13), and known compounds stemofoline (1), (2′S)-hydroxystemofoline (2), stemofuran E (4), stemofuran F (5), stemofuran J (6), and stilbostemin F (7) have been isolated from the root extracts of Stemona aphylla. The structures and relative configurations of these new compounds have been determined by spectroscopic data interpretation and from semisynthetic studies. These natural and semisynthetic alkaloids were tested for acetylcholinesterase inhibitory activities and were found to be 10-20 times less active than 1′,2′-didehydrostemofoline itself. Stemofurans 4, 6, 8, 11, and 13 were tested for their antibacterial and antifungal activities. Three of these showed antibacterial activities against MRSA with MIC values of 15.6 μg/mL

Fimbricalyx A, a novel phenanthrenone derivative having a rare 2H-benz[e]inden-2-one substructure

Fimbricalyx A (1), a novel phenanthrenone derivative having a rare 2H-benz[e]inden-2-one substructure, was isolated from the root extract of Strophioblachia fimbricalyx. The structure of 1 was elucidated on the basis of the NMR and MS data and confirmed by X-ray crystallography. This compound showed cytotoxicity against KB, MCF7 and NCI-H187 cancer cells with IC50 values of 38.4, 28.7 and 8.3 μg/mL, respectively. A possible biosynthesis of 1, via a ring-contracted p-quinone methide intermediate derived from a phenanthrenone precursor, is proposed

Bioactive compounds from the roots of Strophioblachia fimbricalyx

Eight new compounds, fimbricalyxs B-D (1-3), fimbricalyxanhydrides A and B (4, 5), and fimbricalyxlactones A-C (6-8), together with three known compounds, trigonostemone (9), 3,6,9-trimethoxyphenanthropolone (10), and fimbricalyx A (11), were isolated fr