A potent antibacterial indole alkaloid from Psychotria pilifera.

A new strychnine alkaloid, 16,17,19,20-tetrahydro-2,16-dehydro-18-deoxyisostrychnine (1), and fourteen known alkaloids were isolated from the leaves of Psychotria pilifera. Their structures were identified on the basis of extensive spectroscopic analysis, as well as by comparison with the reported spectroscopic data. The new alkaloid (1) exhibited potent antibacterial activity against Escherichia coli, equivalent to cefotaxime with MIC value of 0.781 µg/ml.

Non-alkaloid constituents of Vinca major.

The present study was designed to investigate the non-alkaloid compounds from the leaves and stems of Vinca major cultivated in Yunnan Province, China. The compounds were isolated using chromatographic techniques. The structures were elucidated by 1D- and 2D-NMR spectroscopic methods in combination with UV, IR, and MS analyses. The 1, 1-diphenyl-2-picrylhydrazyl (DPPH)-scavenging activity of Compounds 1-7 were evaluated. One new iridoid glycoside (compound 1), together with 11 known compounds, were isolated from Vinca major. Compounds 1, 5, and 6 showed moderate DPPH-scavenging activity, with IC50 values being 70.6, 32.8, and 62.2 µmol·L(-1), respectively. In conclusion, compound 1 is a newly identified iridoid glycoside with moderate antioxidant activity.

Monoterpenoid Indole Alkaloids from Inadequately Dried Leaves of Alstonia scholaris.

Six new indole alkaloids, named alstoniascholarines L-Q (1-6), together with nineteen known analogues were isolated from the inadequately dried leaves of Alstonia scholaris. Their structures were elucidated on the basis of extensive analysis of spectroscopic data and by comparison of their physical and spectroscopic data with the literature values. In addition, the new alkaloids were tested for their cytotoxic and neurite outgrowth-promoting activities.

Chemical Constituents from the Stems of Ecdysanthera rosea.

One new eudesmane sesquiterpenoid (1) named ecdysantherol A and two new benzene derivatives ecdysantherols B (2) and C (3), together with five known benzene derivatives (4-8) were isolated from the stems of Ecdysanthera rosea. The structures of the new compounds were elucidated by extensive spectroscopic methods and X-ray diffraction. The known compounds were identified by the comparison of their spectroscopic data with reported literature data. Compound 1 showed moderate antibacterial activity against the Providensia smartii with MIC value of 12.5 µg/mL.

New antimicrobial pregnane glycosides from the stem of Ecdysanthera rosea.

Phytochemical investigation on the stem of Ecdysanthera rosea led to the isolation of eight new C-21 pregnane glycoside ecdysosides A-H (1-8), together with one known pregnane glycoside ecdysantheroside A (9). Their structures were elucidated based on extensive spectroscopic data (MS, IR, 1D and 2D NMR) analysis, as well as comparison with the reported literature data. Antimicrobial activities of all the compounds were evaluated against bacteria and yeasts. Compounds 1, 9, 3 and 5 exhibited moderate antibacterial activities against respective Enterococcus faecalis and Providensia smartii, with MIC value of 12.5 µg/mL. Compound 8 showed significant anti-yeast activity against Cryptococcus neoformans with MIC value of 12.5 µg/mL.

Limonoid and Steroidal Saponin from Azadirachta indica.

A new limonoid, 17-(5-methoxy-2-oxofuran-3-yl)-28-deoxonimbolide (1), and a new C21 steroidal saponin, 2α,4α-dihydroxy-pregn-5-en-16-one-3α-O-D-glucopyranoside (2), together with 11 known compounds were isolated from the methanol extract of the leaves of Azadirachta indica. The structures were elucidated by means of spectroscopic analysis and putative biosynthetic origins. All the compounds were evaluated for their antibacterial activities against six bacterial strains.

Isolation and identification of compounds responsible for antioxidant capacity of Euryale ferox seeds.

Euryale ferox seed is consumed medicinally or for food in China. The present study revealed it to contain significant antioxidant activity, which may be associated with its medical applications as a proteinuria inhibitor of diabetic nephropathy. This study resulted in the identification of 3 new sesquineolignans, named euryalins A-C (1-3), and 16 known compounds, which were all first isolated from this plant apart from 5,7,4-trihydroxy-flavanone. The antioxidant potential of the partial isolates was evaluated using the DPPH radical scavenging assay and mesangial cellular assay. Compounds 2, rel-(2α,3ß)-7-O-methylcedrusin (4), syringylglycerol-8-O-4-(sinapyl alcohol) ether (5), and (+)-syringaresinol (7) were found to be most active on DPPH assay, whereas compounds 2, 4, 7, (1R,2R,5R,6S)-2-(3,4-dimethoxyphenyl)-6-(3,4-dihydroxyphenyl)-3,7-dioxabicyclo[3.3.0]octane, and buddlenol E could significantly inhibit high glucose-stimulated reactive oxygen species production in mesangial cells. The results suggested that E. ferox seed could be considered as an excellent source of natural antioxidants and is useful in the prevention of diabetic nephropathy.