Comparative Study of Phenolic Profile, Antioxidant Capacity, and Color-composition Relation of Roselle Cultivars with Contrasting Pigmentation.

Roselle is a plant that accumulates anthocyanins significantly, hence its importance as food coloring and as a source of antioxidant compounds for human health. This study was aimed to determine phenolic composition and antioxidant capacity of methanolic extracts, and beverages obtained from native roselle cultivars in Mexico (Negra, Sudan, Rosa and Blanca) with different degrees of pigmentation, and to establish the color-composition relationship. Chromatographic methods were used to determine phenolic compounds: flavanols, flavonols, benzoic, hibiscus and phenolic acids as well as two main anthocyanins (cyanidin 3-sambubioside and delphinidin 3-sambubioside). The antioxidant capacity was evaluated by ABTS and FRAP assays. Tristimulus colorimetry showed to be a useful technique to determine the color-composition relationship, leading to equations that allowed to predict anthocyanin content of roselle (R > 0.84). Also, a stepwise linear discriminant analysis (SLDA) was developed in order to classify roselle cultivars. The obtained mathematical model could be an important tool to be used in colorimetric characterization of functional compounds used in food processing.

Assessment of the differences in the phenolic composition and color characteristics of new strawberry (Fragaria x ananassa Duch.) cultivars by HPLC-MS and Imaging Tristimulus Colorimetry.

The phenolic composition (by HPLC-DAD-MS) and color characteristics (by Imaging Tristimulus Colorimetry) of four strawberry cultivars that have shown good climate adaptation to subtropical area (Nikte, Zamorana, Jacona and Pakal) have been assessed. 24 monomeric phenolics were identified, including 15 anthocyanins, 5 phenolic acids, 1 flavanol and 4 flavonols. Nikte and Zamorana showed the highest phenolic potential mainly due to their higher content of anthocyanins, while Pakal was richer in phenolic acids. Regarding color, Nikte and Zamorana were the more similar cultivars having the lowest values of lightness and hue. On the contrary, the color of Pakal was quite different from all the rest, due to the specific distribution between pelargonidin and cyanidin. The inclusion of both phenolic and colorimetric information in the Linear Discriminant Analysis allowed reaching very good discriminations among cultivars.

Carotenogenic gene expression and ultrastructural changes during development in marigold.

Marigold (Tagetes erecta) flowers are a good source of carotenoids and can be used as a model studies on pigmentation during flower development. They show different levels of pigmentation caused by lutein. Here we describe the expression of several genes in the carotenoid biosynthetic pathway: phytoene synthase (Psy), phytoene desaturase (Pds), lycopene beta-cyclase (Lcy-b) and lycopene epsilon-cyclase (Lcy-e). cDNA inserts from isolated clones were 1376-1916bp long. The predicted amino acid sequences showed from 66 to 100% homology with other reported sequences (NCBI gene bank). Northern blot analyses of three varieties of marigold showed that most gene transcripts were expressed during flower development. The ultrastructural changes that occurred during plastid differentiation in flower morphogenesis were analyzed, and pigment accumulation among varieties was evaluated. The pigment deposition in specific structures (lipidic vesicles) during flower development was demonstrated.