Chun-Mao Yuan

Peganumine A, a β-Carboline Dimer with a New Octacyclic Scaffold from Peganum harmala

Peganumine A (1), a new dimeric β-carboline alkaloid characterized by a unique 3,9-diazatetracyclo[6.5.2.0(1,9).0(3,8)]pentadec-2-one scaffold, was isolated from the seeds of Peganum harmala. The structure including the absolute configuration was determined by spectroscopic data, X-ray crystallography, ECD calculation, and CD exciton chirality approaches. Compound 1 showed moderate cytotoxic activity against MCF-7, PC-3, and HepG2 cells and selective effects on HL-60 cells with an IC50 value of 5.8 μM.

Aphanamixoid A, a Potent Defensive Limonoid, with a New Carbon Skeleton from Aphanamixis polystachya

Aphanamixoid A (1), a limonoid with a new carbon skeleton, along with its biogenetically related limonoid aphanamixoid B (2), was isolated from the leaves and twigs of Aphanamixis polystachya . Their structures with the absolute stereochemistry were determined by spectroscopic analysis, X-ray crystallography and computational methods. The significant antifeedant activity of 1 against the generalist plant-feeding insect Helicoverpa armigera (EC50 = 0.015 μmol/cm(2)) suggested it may be a potent defensive component of A. polystachya.

Isolation and Asymmetric Total Synthesis of Perforanoid A

A novel limonoid, perforanoid A, was isolated, and an asymmetric total synthesis was achieved in 10 steps. The key steps are chiral tertiary aminonaphthol mediated enantioselective alkenylation of an aldehyde to an allylic alcohol, Pd-catalyzed coupling of the allylic alcohol with vinyl ether to form the γ-lactone ring, and cyclopentenone ring formation through a Rh-catalyzed Pauson-Khand reaction. Preliminary studies show that perforanoid A is cytotoxic towards HEL, K562, and CB3 tumor cell lines.

Two Unusual Polycyclic Polyprenylated Acylphloroglucinols, Including a Pair of Enantiomers from Garcinia multiflora.

Two polycyclic polyprenylated acylphloroglucinols, garcimulins A and B ((±)-1 and 2), including a pair of enantiomers with the unique caged tetracyclo[5.4.1.1(1,5).0(9,13)]tridecane skeleton were isolated from Garcinia multiflora. Their structures and absolute configurations were determined by extensive analysis of spectroscopic data and electronic circular dichroism (ECD) calculations. Compounds 1 and 2 exhibited cytotoxic activities against five human cancer cell lines in vitro (IC50 3.42-13.23 μM). The acidification of lysosomes in HeLa cell was obviously affected by compound 2.

Cytotoxic Limonoids from Melia azedarach

Five new compounds (1-5), including two limonoids, one triterpenoid, one steroid, and one sesquiterpenoid, along with nine known limonoids (6-14), were isolated from the bark of Melia azedarach. The structures of the new compounds were elucidated by 2D NMR spectroscopy and mass spectrometry. The isolated compounds as well as three acetylated derivatives of 9 were evaluated for their cytotoxicities against five human tumor cell lines (HL-60, SMMC-7721, A-549, MCF-7, and SW480) by an MTT assay. Seven limonoids (1, 6, 7, 8, 9, 9b, and 9c) showed significant inhibitory activities against tested cell lines with IC50 values ranging from 0.003 to 0.555 µM, and their preliminary structure-activity relationships are also discussed.

Pegaharmalines A and B, two novel β-carboline alkaloids with unprecedented carbon skeletons from Peganum harmala

Pegaharmalines A (1) and B (2), two novel β-carboline alkaloids with unprecedented carbon skeletons, were isolated from the seeds of Peganum harmala. Their structures were determined by spectroscopic methods and the absolute configuration of 1 was elucidated by CD analysis. 1 and 2 exhibited significant cytotoxicities on HL-60 cells with IC50 values of 9.4 and 13.6 μM, respectively.

Khayseneganins A-H, Limonoids from Khaya senegalensis

Eight new limonoids, khayseneganins A-H (1-8), and 31 known limonoids were isolated from the leaves and twigs of Khaya senegalensis. The structures of the new compounds were elucidated by 2D-NMR spectroscopy and mass spectrometry, and the absolute configuration of 1 was determined by the CD exciton chirality method. Compounds 9, 10, 12, and 15 showed antimicrobial activities against Pseudomonas aeruginosa, MRSA 92(#), and MRSA 98(#), all with a MIC value of 12.5 μg/mL.

Senegalensions A-C, three limonoids from Khaya senegalensis.

NSFC [30830114]; Ministry of Science and Technology [2009CB522300, 2009CB940900]; Young Academic and Technical Leader Raising Foundation of Yunnan Province [2010CI047]

Aphagrandinoids A-D, cycloartane triterpenoids with antibacterial activities from Aphanamixis grandifolia.

Three new cycloartane triterpenoids, aphagrandinoids A-C (1-3), and a new natural product, aphagrandinoid D (4), together with a known compound, were isolated from the leaves and twigs of Aphanamixis grandifolia. Their structures were elucidated by extensive NMR and MS techniques. Aphagrandinoid A (1), a 29-nor-cycloart triterpenoid, features with a sprio ring system at the side chain, while aphagrandinoid C (3) is a pentnortriterpenoid. Antibacterial activities of these five compounds were also evaluated. Compounds 1 and 5 showed weak antibacterial activities (MIC values: 1.57-3.13μg/mL) against Staphylococcus aureus, MRSA 92(#), and MRSA 98(#).

Trigohowilols A−G, Degraded Diterpenoids from the Stems of Trigonostemon howii

Two new degraded diterpenoids, trigohowilols A (1) and B (2), four new heterodimers, trigohowilols C-F (3-6), one new homodimer, trigohowilol G (7), and three known degraded diterpenoids (8-10) were isolated from the methanol extract of the stems of Trigonostemon howii. Compounds 1-7 were evaluated for their cytotoxic activity against five human tumor cell lines by an MTT assay, and trigohowilols E (5) and F (6) exhibited inhibitory activity with IC50 values ranging from 2.33 to 12.57 μM. Moreover, compounds 1-6 showed weak antimicrobial activities (MIC values: 6.25-25 μg/mL) against Staphylococcus aureus, Pseudomonas aeruginosa, MRSA 92(#), and MRSA 98(#) using a 2-fold dilution method.