Current advances of Carthamus tinctorius L.: a review of its application and molecular regulation of flavonoid biosynthesis

Safflower is a valuable medicinal plant due to its diverse flavonoids, known as safflower yellow (SY) and safflower red (SR) pigments, which are popular in the fields of medicine, food and natural dye. The main pharmacological ingredient in safflower is SY pigment, which is a kind of water-soluble flavonoids, such as hydroxysafflor yellow A (HSYA). In contrast, SR pigment mainly contains carthamin, which is sparingly soluble in water and has a historic reputation as a red colorant. These flavonoids from both SY and SR pigments belong to C-glucosylquinochalcones and their derivatives, which are only existed in safflower. Over the past few decades, genetics, molecular biology and multi-omics strategies have been used to study flavonoid biosynthesis in safflower. However, there has not been a comprehensive summary of the application and molecular progress of safflower flavonoid biosynthesis. In this review, we summarize the various applications of safflower in medicine, natural dye, and food, as well as the molecular regulation of flavonoid biosynthesis. We also propose future research directions on safflower flavonoids. This work aims to provide an objective national and international review of literature on the application and biosynthetic regulation of safflower flavonoids.