Nattaya Ngamrojnavanich

Selective determination of homocysteine levels in human plasma using a silver nanoparticle-based colorimetric assay

The first use of silver nanoparticles (AgNPs) for the rapid, simple, and selective determination of homocysteine (Hcy) levels in human plasma was studied. Hcy and five other amino acids, including cysteine (Cys), could be distinguished by their different aggregation kinetics, which caused a change in the visible color and a shift in the UV-vis absorption spectra. The difference in the cross-linking (aggregation) rate between Hcy and Cys was used as the basis for developing a selective probe for Hcy and allowed the detection of Hcy in the linear range of 2-12 μM (R(2)=0.9936). The limits of detection and quantification were found to be 0.5 μM and 1.7 μM, respectively. To investigate its selectivity and potential applicability, this AgNP-based method was successfully applied for the determination of Hcy levels in actual biological (human plasma) samples, where the determined levels of Hcy were within the error range of the measured level using the traditional chemiluminescence microparticle immunoassay (CMIA). Thus, the use of AgNPs is a feasible and potentially reliable method for the determination of Hcy levels in biological samples.

Cytotoxic labdane diterpenoids from Croton oblongifolius

Three labdane diterpenoids, 2-acetoxy-3-hydroxy-labda-8(17),12(E)-14-triene, 3-acetoxy-2-hydroxy-labda-8(17),12(E)-14-triene, and 2,3-dihydroxy-labda-8(17),12(E),14-triene were isolated from stem bark of Croton oblongifolius. Their structures were established by spectroscopic data, and each was also tested for cytotoxicity against various human tumor cell lines. The latter compound showed non-specific, moderate, cytotoxicities against all the cell lines; whereas the first two compounds were less active.

Cassane diterpenoid from Caesalpinia major.

A new cassane diterpenoid, 14-deoxy-epsilon-caesalpin was isolated from the seed kernels of Caesalpinia major and its structure was determined by spectroscopic data.

Diterpenoids from the stem barks ofCroton robustus

Three compounds were isolated from the stem barks ofCroton robustus. Their structures were elucidated as trachyloban-19-oic acid, trachyloban-19-ol and poilaneic acid by spectroscopic analysis. Among them, trachyloban-19-ol and methyl trachyloban-19-oate exhibited weak cytotoxic activity against gastric carcinoma and colon carcinoma with ED50 of 9.2, 9.6 and 8.3, 9.1 μg/mL, respectively.

Oxidized heptenes from flowers of Melodorum fruticosum

Three oxidized heptenes, 7-benzoyloxy-6-oxo-2,4Z-heptadiene-1,4-olide, [7-benzoyloxy-4-hydroxy-1-methoxy-2E,4Z-heptadiene-1,6-dione] and 7-benzoyloxy-6-oxo-2,4E-heptadiene-1,4-olide, were isolated from flowers of Melodorum fruticosum. Their structures were determined by spectral data analysis. The first two compounds exhibited moderate cytotoxicity against a panel of human tumor cell lines, whereas the third was inactive.