Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) has been recognised as an effective technique to analyse car paint. This study was conducted to assess the combination of Py-GC-MS and chemometric techniques to classify car paint primer, the inner layer of car paint system. Fifty car paint primer samples from various manufacturers were analysed using Py-GC-MS, and data set of identified pyrolysis products was subjected to principal component analysis (PCA) and discriminant analysis (DA). The PCA rendered 16 principal components with 86.33% of the total variance. The DA was useful to classify the car paint primer samples according to their types (1k and 2k primer) with 100% correct classification in the test set for all three modes (standard, stepwise forward and stepwise backward). Three compounds, indolizine, 1,3-benzenedicarbonitrile and p-terphenyl, were the most significant compounds in discriminating the car paint primer samples.
Eleven new indole alkaloids, in addition to the previously reported rhazinal (1), and 14 other known alkaloids, were obtained from the Malayan Kopsia singapurensis, viz., kopsiloscines A-F (2-7), 16-epikopsinine (8), kopsilongine- N-oxide (9), 16-epiakuammiline (10), aspidophylline A (11), and vincophylline (12). The structures of these alkaloids were determined using NMR and MS analyses. Rhazinal (1), rhazinilam (17), and rhazinicine (18) showed appreciable cytotoxicity toward drug-sensitive as well as vincristine-resistant KB cells, while kopsiloscines A (2), B (3), and D (5) and aspidophylline A (11) were found to reverse drug-resistance in drug-resistant KB cells.
Hispidacine, an 8,4'-oxyneolignan featuring incorporation of an unusual 2-hydroxyethylamine moiety at C-7, and hispiloscine, a phenanthroindolizidine alkaloid, were isolated from the stem-bark and leaves of the Malaysian Ficus hispida Linn. Their structures were established by spectroscopic analysis. Hispidacine induced a moderate vasorelaxant activity in rat isolated aorta, while hispiloscine showed appreciable antiproliferative activities against MDA-MB-231, MCF-7, A549, HCT-116 and MRC-5 cell lines.
Four alkaloids comprising two vallesamine, one strychnan, and one pyranopyridine alkaloid, in addition to 32 other known alkaloids were isolated from two Malayan Alstonia species, Alstonia pneumatophora and Alstonia rostrata. The structures of these alkaloids were determined using NMR and MS analyses, and in one instance, confirmed by X-ray diffraction analysis. The nor-6,7-secovallesamine alkaloid, pneumatophorine, is notable for an unusual incorporation of a 3-ethylpyridine moiety in a monoterpenoid indole. The rhazinilam-type alkaloids (rhazinicine, nor-rhazinicine, rhazinal, and rhazinilam) showed strong cytotoxicity toward human KB, HCT-116, MDA-MB-231, and MRC-5 cells, while pneumatophorine, the uleine alkaloid undulifoline, and the strychnan alkaloids, N4-demethylalstogustine and echitamidine, induced concentration dependent relaxation in phenylephrine-precontracted rat aortic rings.
Eight new indole alkaloids (1-8) belonging to the rhazinilam-leuconolam-leuconoxine group, in addition to 52 other alkaloids, were isolated from the stem-bark extract of Leuconotis griffithii, viz., nor-rhazinicine (1), 5,21-dihydrorhazinilam-N-oxide (2), 3,14-dehydroleuconolam (3), and leuconodines A-E (4-8). The structures of these alkaloids were determined using NMR and MS analyses and in some instances confirmed by X-ray diffraction analyses. Alkaloids 1, 5, and 7 showed only moderate to weak cytotoxicity toward KB cells (IC50 12-18 μg/mL), while 8 showed moderate activity in reversing MDR in vincristine-resistant KB cells.
Tengerensine (1), isolated as a racemate and constituted from a pair of bis-benzopyrroloisoquinoline enantiomers, and tengechlorenine (2), purified as a scalemic mixture and constituted from a pair of chlorinated phenanthroindolizidine enantiomers, were isolated from the leaves of Ficus fistulosa var. tengerensis, along with three other known alkaloids. The structures of 1 and 2 were determined by spectroscopic data interpretation and X-ray diffraction analysis. The enantiomers of 1 were separated by chiral-phase HPLC, and the absolute configurations of (+)-1 and (-)-1 were established via experimental and calculated ECD data. Compound 1 is notable in being a rare unsymmetrical cyclobutane adduct and is the first example of a dimeric benzopyrroloisoquinoline alkaloid, while compound 2 represents the first naturally occurring halogenated phenanthroindolizidine alkaloid. Compound (+)-1 displayed a selective in vitro cytotoxic effect against MDA-MB-468 cells (IC50 7.4 μM), while compound 2 showed pronounced in vitro cytotoxic activity against all three breast cancer cell lines tested (MDA-MB-468, MDA-MB-231, and MCF7; IC50 values of 0.038-0.91 μM).