Total phenolics, ascorbic acid, and betalain contents of differently colored cactus pear clones (nine Opuntia ficus-indica [L.] Mill. clones and one O. robusta Wendl. clone) were investigated and related to their respective antioxidant potential assessed by Trolox-equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays. TEAC and ORAC values were very highly correlated with each other and also with values for total phenolics, betalain contents, and ascorbic acid concentrations. Total phenolics had the greatest contribution to ORAC and TEAC values. High-performance liquid chromatography (HPLC)-diode array detector (DAD)-tandem mass spectrometry (MS/MS) measurements of cactus pear juices permitted the differentiation of the clones based on variations in pigment patterns and betalain concentrations. The red and yellow betalains were absent in lime green colored cactus fruits. The ratio and concentration of these pigments were responsible for the yellow, orange, red, and purple colors in the other clones. Progeny of purple and lime green colored parents were characterized by 12% and 88% of plants bearing lime green and purple fruit, respectively. This implies that the genes for betalain production were lacking in the lime green fruits but could be provided by a parent with a complete set of genes, that is, purple fruits. Besides known pigments typical of Cactaceae, two unexpected betalains were identified. Whereas gomphrenin I was found for the first time in tissues of cactus plants, methionine-betaxanthin has never been described before as a genuine betalain. In addition to their alleged health-promoting properties, various combinations of yellow betaxanthins and red-purple betacyanins may allow the development of new food products without using artificial colorants.

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The results of Raman-vibronic double resonance experiments on benzene dimer are reported. The results were obtained by mass-selective, ionization-detected stimulated Raman spectroscopies. The data pertain to the Vii V2, and V6 fundamentals of n~merous dimer isotopomers. The results are discussed in terms of the geometry of the dlmer. They show that the species is characterized by two inequivalent benzene sites with one of the sites of low and the other of higher symmetry. These two sites give rise to different Raman resonance frequencies, different vibrational dynamics, and markedly different S I~SO vibronic spectra. It is argued that all of the experimental results are consistent ~ith a T-sha~ed equilibrium geometry in which the benzene moiety at the top of the T IS freely rotatmg about its C 6 axis.

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