Paul Owusu Donkor

The determination of the chemical structure of an isolated vasodilatory molecule from Ludwigia octovalvis (Jacq.) P.H. Raven (Onagraceae) was undertaken. This molecule was isolated from n-butanolic extract using bioassay-guided isolation with preparative plate chromatographic techniques and its structure was determined using spectroscopy (UV, 1D- and 2D NMR, MS). The

Two pairs of phenylpropanoid enantiomers, (+)-(7S,8S)-alatusol D (1a), (−)-(7R,8R)-alatusol D (1b), (−)-(7S,8R)-alatusol D (2a) and (+)-(7R,8S)-alatusol D (2b) were isolated from the leaves of Eucommia ulmoides Oliver. Among them, 1a and 2b were firstly obtained by chiral enantiomeric resolution. Their structures were elucidated based on extensive spectroscopic analysis and the induced CD (ICD) spectrum caused by adding Mo₂(AcO)₄ in DMSO. All compounds were tested on Hep G2 tumor cell lines. However, none of the compounds showed potential cytotoxic activity against Hep G2 in vitro.

Two pairs of new phenolic enantiomers, (+)-eucophenolic A (1a), (-)-eucophenolic B (1b), (-)-eucophenolic C (2a), (+)-eucophenolic D (2b) were isolated from the leaves of Eucommia ulmodies Oliver by chiral enantiomeric resolution. Their structures were elucidated based on extensive spectroscopic analysis. The absolute configurations of 1a/1b and 2a/2b were determined by empirical method and the calculated ECD and OR. All compounds were tested for Hep G2 tumour cell lines. However, no compounds showed potential cytotoxic activities against Hep G2 in vitro.

1. Corydaline, an isoquinoline alkaloid obtained from the rhizomes of Corydalis yanhusuo, exhibits anti-acetylcholinesterase, anti-angiogenic, anti-allergic and gastric-emptying activities. In this study, a rapid and reliable ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF-MS) method was developed and employed for the comprehensive study of the metabolites of corydaline in rats. 2. Altogether, 43 metabolites were identified in the plasma (11), bile (9), urine (34) and feces (21) of rats after oral administration of corydaline at a dose of 4.5mg/kg. 3. It was demonstrated that demethylation, hydroxylation, sulfation and glucuronidation were the major metabolic transformation pathways. Among these, two metabolites were identified as tetrahydropalmatine and isocorybulbine, and 33 phase I and phase II products were inferred to be new metabolites arising from the in vivo metabolism of corydaline. 4. Importantly, this research provides scientific and reliable support for full understanding of the metabolic profiles of corydaline and the results could help to elucidate its safety and efficacy.

Nine pairs of megastigmane enantiomers (1a/1b–9a/9b), comprising two new compounds (6S,9R)-blumenol C (7b), (6S,9S)-blumenol C (8b), two pairs of enantiomers (+)-(6R)-eucomegastigmane A (1a), (−)-(6S)-eucomegastigmane A (1b), (+)-(3S,4S)-eucomegastigmane B (5a), (−)-(3R,4R)-eucomegastigmane B (5b) isolated by chiral resolution firstly, and twelve known compounds, were isolated from the leaves of Eucommia ulmoides Oliver. Their structures were elucidated based on extensive spectroscopic analysis. Absolute configurations of the megastigmane enantiomers were assigned by comparing experimental ECD and OR with calculated ECD and OR. Docking-based virtual screening of all compounds showed that megastigmane enantiomers have weak intermolecular interactions with the binding site residues of angiotensin-converting enzyme (ACE) and angiotensin II type 1 receptor (AT₁R).

Germacrane-type sesquiterpenes, with a flexible 10-membered ring unit as the structural and conformational features, play a central role in the biosynthesis and synthesis of other sesquiterpenes. In this report, two pairs of new sesquiterpene alkaloids, (+)/(−)-phaeocaulin A [(+)-1/(−)-1] and B [(+)-2/(−)-2], and two pairs of new sesquiterpenes, (+)/(−)-phaeocaulin C [(+)-3/(−)-3] and D [(+)-4/(−)-4], along with one related known analog (5), were isolated from the rhizomes of Curcuma phaeocaulis. The absolute configurations of (+)-1/(−)-1, (+)-2/(−)-2, (+)-3/(−)-3 and (+)-4/(−)-4 were unambiguously determined by analysis of single-crystal X-ray diffractions and quantum chemical electronic circular dichroism (ECD) method. It is noteworthy that (+)/(−)-phaeocaulin A [(+)-1/(−)-1] and B [(+)-2/(−)-2] are two pairs of rare N-containing germacrane-type sesquiterpenes. A possible biogenetic pathway for 1–5 was postulated. All of the isolated compounds were tested for their inhibitory activity against LPS-induced nitric oxide production in RAW 264.7 macrophages.

1. Physalin A is a bioactive withanolide isolated from the natural plant Physalis alkekengi var. franchetii (Solanaceae), a common traditional Chinese herbal medicine. This study aims to investigate the metabolites of physalin A in vivo. 2. Two metabolites (M1 and M2) were characterized as sulfonate metabolites in the feces obtained from rats treated with physalin A orally at a dose of 15 mg/kg/day for 3 days, by application of a UPLC-Q/TOF-MS method. Furthermore, formation of the two sulfonate metabolites was verified by chemical synthesis and NMR, including ¹H NMR, ¹³C NMR and two-dimensional NMR. The structures of M1 and M2 were identified to be 3α-sulfo-2,25β,27-trihydrophysalin A and 3α,27-disulfo-2,25α-dihydrophysalin A, respectively. 3. In summary, this study indicated that physalin A could be biotransformed to sulfonate metabolites with strong polarity, which contributed to the elimination of physalin A. A rare metabolic pathway has been revealed in this study.