Identification of Enzymatic Cleavage Products of -Carotene-Rich Extracts of Kale and Biofortified Maize.

Provitamin A carotenoids in plant foods provide more than 80% of vitamin A intake for people in developing countries. Therefore, the conversion efficiency of -carotene to vitamin A is important, as it determines the effectiveness of plant foods as sources of vitamin A in humans. The objective of this study was to determine the effect of plant food antioxidants such as -tocopherol, -tocopherol, -tocotrienol, -tocotrienol and total -oryzanol on the cleavage of -carotene in vitro. Rat intestinal mucosa post mitochondrial fractions were incubated with -carotene-rich extracts of kale and biofortified maize for an hour at 37°C. Rat intestinal mucosa post mitochondrial fractions were also incubated with -carotene in the presence of either -tocopherol, -tocopherol, -tocotrienol, -tocotrienol or -oryzanol for 60 min at 37°C. The -carotene cleavage products were extracted and analyzed by an HPLC equipped with a C18 column at 340nm and 450nm. When -carotene alone was incubated without intestinal mucosa homogenate (control), no cleavage products were detected. When -carotene alone was incubated with intestinal mucosa homogenate, -apo-13-carotenone, -apo-14-carotenal, retinal, retinol and retinoic acid were formed. However, incubation of -carotene with either -tocopherol, -tocopherol or -tocotrienol resulted in a 10 fold inhibition of -apo-14-carotenal and -apo-13-carotenone formation. Antioxidant rich biofortified maize extract incubated with postmitochondrial fraction produced less -apo-13-carotenone compared to the kale extract. These results suggest that antioxidants inhibit the cleavage of -carotene and the formation of excentric cleavage products (-apo-13-carotenone, -apo-14-carotenal).