beta-Cryptoxanthin has been isolated from abalone, fish eggs, and many higher plants. beta-Cryptoxanthin is a major source of vitamin A, often second only to beta-carotene, and is present in fruits such as oranges, tangerines, and papayas (PMID: 8554331). Frequent intake of tropical fruits that are rich in beta-cryptoxanthin is associated with higher plasma beta-cryptoxanthin concentrations in Costa Rican adolescents. Papaya intake was the best food predictor of plasma beta-cryptoxanthin concentrations. Subjects that frequently consumed (i.e. greater or equal to 3 times/day) tropical fruits with at least 50 micro g/100 g beta-cryptoxanthin (e.g. papaya, tangerine, orange, watermelon) had twofold the plasma beta-cryptoxanthin concentrations of those with intakes of less than 4 times/week (PMID: 12368412). A modest increase in beta-cryptoxanthin intake, equivalent to one glass of freshly squeezed orange juice per day, is associated with a reduced risk of developing inflammatory disorders such as rheumatoid arthritis (PMID: 16087992). Higher prediagnostic serum levels of total carotenoids and beta-cryptoxanthin were associated with lower smoking-related lung cancer risk in middle-aged and older men in Shanghai, China (PMID: 11440962). Consistent with inhibition of the lung cancer cell growth, beta-cryptoxanthin induced the mRNA levels of retinoic acid receptor beta (RAR-beta) in BEAS-2B cells, although this effect was less pronounced in A549 cells. Furthermore, beta-cryptoxanthin transactivated the RAR-mediated transcription activity of the retinoic acid response element. These findings suggest a mechanism of anti-proliferative action of beta-cryptoxanthin and indicate that beta-cryptoxanthin may be a promising chemopreventive agent against lung cancer (PMID: 16841329). Cryptoxanthin is a natural carotenoid pigment. It has been isolated from a variety of sources including the petals and flowers of plants in the genus Physalis, orange rind, papaya, egg yolk, butter, apples, and bovine blood serum. In a pure form, cryptoxanthin is a red crystalline solid with a metallic lustre. It is freely soluble in chloroform, benzene, pyridine, and carbon disulfide. In the human body, cryptoxanthin is converted into vitamin A (retinol) and is therefore considered a provitamin A. As with other carotenoids, cryptoxanthin is an antioxidant and may help prevent free radical damage to cells and DNA, as well as stimulate the repair of oxidative damage to DNA. Structurally, cryptoxanthin is closely related to beta-carotene, with only the addition of a hydroxyl group. It is a member of the class of carotenoids known as xanthophylls.