Utilization of a natural β-carotene stereoisomers mixture from the fungus Phycomyces blakesleeanus as a source of vitamin A and β-carotene in rats' diet

Abstract

Phycomyces blakesleeanus, a β-carotene—producing fungi, has been tested as a source of vitamin A and β-carotene in the rat diet. The β-carotene in the fungi is composed of 80–90% of the all- trans stereoisomer, and the rest is the 9- cis stereoisomer. Female weanling rats were fed a vitamin A-deficient diet for 60 days. Thereafter, the rats were divided into groups and fed the vitamin A-deficient diet supplemented with synthetic crystalline β-carotene powder or fungal powder to levels of 12,24, and 48 mg β-carotene/kg diet. A diet supplemented with the 9- cis-rich Dunaliella bardawil powder to a level of 24 mg β-carotene/kg was also employed. Following a 10-day feeding period, samples were taken for plasma and liver analyses of retinol, retinyl esters, and β-carotenes. Liver analyses revealed a higher conversion rate of β-carotene to vitamin A and a higher β-carotene accumulation in the rats fed the diets supplemented with fungal or algal powder, as compared to those supplemented with synthetic β-carotene. A significant correlation was found between the total β-carotene accumulated in the liver and the content of dietary 9- cis β-carotene. The conversion of β-carotene to retinol in the liver was found to be affected by the dietary concentration of the carotenoid. The lower the β-carotene concentration in the feed, the higher the conversion to retinol. This inverse relation was also observed for total β-carotene accumulation, its 9- cis:all- trans ratio and for retinol:retinyl palmitate ratio in the livers. These studies demonstrate the possibility of using dried P. blakesleeanus mycelium as a natural source of vitamin A and β-carotene in the rat diet. The 9- cis β-carotene was shown to be of lower vitamin A biopotency than the all- trans β-carotene. However, its contribution to enhanced accumulation of vitamin A and β-carotene in rats' livers seems to be of high importance.