Mass spectrometry of onium compounds—IX: On the evaporation of anilinium oxides. Ionization potential measurements

o-N,N,N-Trimethylanilinium oxide is evaporated structurally unchanged, admixed with the corresponding transalkylated ether. The ionization potential for the anilinium oxide was determined as 6·8 eV which was 0·8 eV lower than for the corresponding ether. An explanation for the unusually low IP value is advanced. In IP measurements in binary mixtures the semi-log plot method showed parallel curves for different compositions in the gas phase, but no linear relationship between the recorded IP and composition was found. Appearance potential measurements show that the energy of the zwitterion in the gas phase is at least 10 kcal/mol higher than in the corresponding ether.     

Isoshamixanthone: a new pyrano xanthone from endophytic Aspergillus sp. ASCLA and absolute configuration of epiisoshamixanthone

Abstract

Isoshamixanthone (1), a new stereoisomeric pyrano xanthone together with the previously known fungal metabolites, epiisoshamixanthone (2), sterigmatocystin (3), arugosin C (4), norlichexanthone (5), diorcinol (6), ergosterol and methyllinoleate, were obtained from the endophytic fungal strain Aspergillus sp. ASCLA isolated from leaf tissues of the medicinal plant Callistemon subulatus. The chemical structure of the new xanthone (1) was elucidated by extensive 1D, 2D NMR, and ESI HR mass measurements, and by comparison with literature data. The constitutions and absolute configurations of 1 and epiisoshamixanthone (2) were additionally confirmed by X-ray crystallography. Compounds 1,2 were evaluated for their potential anticancer activity using the human cervix carcinoma cell line (KB-3-1). The antimicrobial activities of the fungal extract and compounds 1,2 were studied using a panel of pathogenic microorganisms as well.