No abstract

Improved analytical techniques for bitter limonoids in citrus and citrus juices can expedite the evaluation of freeze-induced citrus damage for citrus growers and juice quality for citrus juice producers. Microbore normal-phase and reverse-phase chromatography coupled to a mass spectrometer operating in a positive ion atmospheric pressure chemical ionization and electrospray ionization modes were found to be rapid, selective, and sensitive methods for the analysis of the bitter limonoids limonin and nomilin in citrus juices. Analysis was performed on a chloroform extract of citrus juice to which an internal standard was added. The methods are capable of detecting citrus limonoids in citrus juice in the 60-200 picogram range and quantifying citrus juice limonoids in concentrations as low as 120 picograms. An accurate "total limonoid bitterness" in citrus juice, as represented by the combined occurrence of limonin and nomilin, is easily determined by these methods.

Orange carrots are well known for their nutritional value as producers of ß-carotene, a vitamin A precursor. Lesser known, is their ability to accumulate antioxidants such as chlorogenic acid. Chlorogenic acid is produced through the same biosynthetic pathway that produces lignins, anthocyanins, flavonols and isoflavonoids, the phenylpropanoid pathway. This pathway can be induced by UV-B light and wounding to produce large amounts of chlorogenic acid. We identified a number of the carrot structural genes in this pathway and their proposed regulators in carrot root slices and analyzed their expression in response to UV-B light exposure using real-time PCR. Our results indicate that not only does the expression of the structural genes correlate with their proposed regulators, including DcHY5 and others, but also correlate with chlorogenic acid production. Our results indicate that the HY5-UVR8 signaling network may exist and function in carrot roots.