Chemical constituents of Isodon melissoides.
Four new diterpenoids, melissoidesin E (1), F (2), G (4) and H (5), together with one known diterpenoid and two lignan glycosides, were isolated from aerial parts of Isodon melissoides. Their structures were established by spectral analysis and comparison with related compounds. The lignan glycosides (compounds 7 and 8) were the first examples to be isolated from the genus Isodon plants.
Three new compounds from Isodon melissoides
Reinvestigation of the aerial parts of Isodon melissoides has afforded two new ent-diterpenoids, melissoidesins V (1) and W (2), together with five known ones, glabcensin W (3), melissoidesin C (4), melissoidesin A (5), melissoidesin B (6) and melissoidesin D (7), one new ionone derivative 3α,4α-isopropyliden-β-ionol (8), as well as three analogues, 3-hydroxy-4-oxo-β-ionol (9), megastigma-7-en-3,5,6,9-tetraol (10) and blumenol A (11), and three phenolic compounds salicylic acid (12), syringic acid (13) and cirsiliol (14). The new structures were elucidated on the basis of spectroscopic techniques, especially the 2D-NMR spectral analysis.
Electrochemical detection of copper(II) at a gold electrode modified with a self-assembled monolayer of penicillamine
A penicillamine (PCA) self-assembled monolayer (SAM) was prepared on a gold electrode. It has been found that the modified electrode exhibited a selective response to copper ions. As demonstrated by cyclic voltammetric experiments, the SAM-based electrode showed an attractive ability to preconcentrate efficiently traces of copper(II) from solutions. Under optimum conditions, the anodic peak current was proportional to the concentration of Cu(II) in the range from 8.0 × 10−7 to 1.0 × 10−4 M with a detection limit of 4.0 × 10−7 M. Moreover, this modified gold electrode is also characterized by excellent repeatability, showing a relative standard deviation of 3.2% for nine successive measurements of 1.0 × 10−5 M Cu(II). The PCA/Au SAM gold electrode was used for the determination of Cu(II) in a tap water sample and the results showed a good agreement with the data obtained by atomic emission spectrometry.