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Richard D. Richins, Laura Hernandez, Barry Dungan, Shane Hambly, F. Omar Holguin and Mary A. O'Connell

Plant pigments represent a source of non-toxic compounds that are used as food or cosmetic coloring agents. Red-fruited varieties of Capsicum annuum can be extracted to isolate the red-colored xanthophylls, capsanthin, and capsorubin. Common commercial processes for this extraction use hexane as the extracting solvent and mild or no heat varieties of Capsicum. In this report, we describe a process for efficient extraction of these red pigments using green chemistry: CO2 supercritical fluid extraction and trapping the pigments in ethanol. Furthermore, we demonstrate that this method can be performed on hot or pungent Capsicum fruit and the resulting pigment sample has very low levels of capsaicinoids, 1 to 2 ppm. This process then can reduce the use of hazardous solvents and expand the type of fruit that can be used for the extraction of red pigments.

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Laura Rodriguez-Uribe, Luz Hernandez, James P. Kilcrease, Stephanie Walker and Mary A. O’Connell

Two key fruit qualities in Capsicum annuum are fruit pungency and color. We characterize 13 New Mexican landraces for fruit quality traits at both the chemical level measuring the capsaicinoids, dihydrocapsaicin, and capsaicin as well as five carotenoids, β-carotene, β-cryptoxanthin, zeaxanthin, violaxanthin, and capsanthin, and at the genetic level sequencing two genes in these landraces, Kas I, a capsaicinoid pathway gene, and Ccs, a carotenoid pathway gene. All of the landraces had unusually high levels of dihydrocapsaicin in comparison with capsaicin levels. The levels of the most abundant red pigment, capsanthin, ranged between 468 and 1007 μg·g−1 dry weight fruit in field-grown fruit, whereas levels of β-carotene were more similar in the landraces (13 to 22 μg·g−1 dry weight fruit). Twelve different Kas I alleles were found in the landraces, which predicted six novel KAS proteins in these landraces. Seven alleles of Ccs were found, which predicted three novel CCS proteins. These results demonstrate that the landraces under cultivation in small farms and pueblos in northern New Mexico are sources of important genetic diversity for Capsicum crops.

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Cristián Vela-Hinojosa, Héctor B. Escalona-Buendía, José A. Mendoza-Espinoza, Juan M. Villa-Hernández, Ricardo Lobato-Ortíz, Juan E. Rodríguez-Pérez and Laura J. Pérez-Flores

Antioxidants, antioxidant capacity, and the expression of isoprenoid metabolism–related genes and two pigmentation-related transcription factors were studied in four native and four hybrid tomato (Solanum lycopersicum) genotypes with different-colored fruit. Red fruit genotypes were associated with greater lycopene, β-carotene, lipophilic antioxidant capacity, and greater chromoplast-specific lycopene β-cyclase (CYC-B) transcript levels. Orange fruit genotypes had greater concentrations of tocopherols and greater transcript levels of homogentisate phytyl transferase (VTE-2), 1-deoxy-D-xylulose phosphate synthase (DXS), and 4-hydroxyphenylpyruvate dioxygenase (HPPD). The yellow fruit genotype was greater in total polyphenol and hydrophilic antioxidant capacity with greater expression of geranylgeranyl reductase (GGDR), phytol kinase (VTE-5), phytoene synthase (PSY) 2, lycopene β-cyclase (LCY-B), SlNAC1, and SINAC4. Greater levels of individual antioxidants were associated with specific coloration of tomato fruit. Moreover, the negative correlations between the expression of PSY1 and VTE-5, and between lycopene and chlorophyll, suggest a balance between carotenoids, tocopherols, and chlorophylls. The results of this study support either the direct commercialization of tomatoes with different color fruit or use of their genotypes in breeding programs to increase antioxidant levels among existing cultivars.