Isolation of Two Quinochalcones from Carthamus tinctorius

摘要

Red and yellow colorants from the safflower florets (Carthamus tinctorius L., Compositae) are applicable to processed foods and soft drinks as color additives, cosmetic rouge, dyes, and medicine [Meselhy et al, 1993]. Almost all of these red and yellow colorants in the petals of safflower are classified as members of the C-glucosylquinochalcone family of flavonoids that occurs only in C. tinctorius [Kazuma et al., 2000]. A red colorant of the safflower, carthamin, is composed of two C-glucosylquinochalcone moieties [Obara and Onodera, 1979]. Two major yellow C-glucosylquinochalcone colorants of safflower are hydroxysafflor yellow A and safflor yellow B [Takahashi et al., 1984; Meselhy et al., 1993]. Besides these two, several other minor quinochalcone colorants, including safflomin A [Onodera et al, 1981], safflor yellow A [Takahashi et al., 1982], safflomin C [Onodera et al., 1989], tinctormin [Meselhy et al., 1993], precarthamin [Kumazawa et al., 1994], anhydrosafflor yellow B [Kazuma et al, 2000], and cartormin [Yin and He, 2000] have been reported. As a part of our ongoing search for chemical constituents from C. tinctorius, we isolated five red and yellow quinochalcones (carthamin, hydroxysafflor yellow A, safflor yellow B, precarthamin, andcartormin) and examined their pH and thermal stability, and antioxidant activity [Kim and Paik, 1997; Yoon et al, 2003; Yoon et al, 2007]. Enzymatic conversion of the yellow colorant precarthamin into the red pigment carthamin was also performed [Cho etal, 2000]. Our continuing work led to the isolation of safflomin C and a related C-glucosylquinochalcone from the BuOH-soluble fraction of the safflower florets. This paper describes the procedures of isolation and the structural elucidation of these two quinochalcones 1 and 2 (safflomin C and isosafflomin C, Fig. 1).