Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: March 20, 1998
Publication Date: N/A
Interpretive Summary: Citrus is a crop that is not only economically important, but, due to its nutritional value, is an important component of the human diet. One of the reasons for its importance is the high levels of antioxidative compounds, including a set of compounds termed the flavonoids. Flavonoids are known to be some of the most potent dietary antioxidants, and thus are critical to maintaining good health. This book chapter summarizes the published reports of the occurrence of the flavonoids in different citrus varieties and in related plant species. The diversity of the structures of these compounds in citrus species is commented on. Results of recent studies of the biosynthesis of these important compounds are presented, and are shown to support certain pathways by which these compounds are made in the fruit tissue.
Technical Abstract: Flavonoids are a distinguishing feature in citrus, and in fact, citrus is the main dietary source of certain important classes of flavonoids. Due to the importance of these compounds to the quality of citrus products, a great deal of research has been done to characterize these compounds in citrus, including citrus relatives in the orange subfamily Aurantioideae. Citrus is particularly rich in flavanones as well as flavones. Most of these compounds occur either as C-glycosides, or as O-glycosides. In addition to these are flavonoids that are highly methoxylated and lack glycosidation. Many of these compounds exhibit important physiological properties in in vitro and in vivo animal studies. The distributions of the different classes of flavonoids among the 33 genera of the Aurantioideae are reviewed, and initial studies indicate that certain species of citrus contain compounds that have yet to be reported. The biosynthetic pathways of the main flavonoids are discussed, and results are presented that support sequential glycosidations of key flavanone intermediates.