β-carotene (beta-carotine) is a strongly colored red-orange pigment abundant in plants and fruits. It is an organic compound and chemically is classified as a hydrocarbon and specifically as a terpenoid (isoprenoid), reflecting its derivation from isoprene units. β-Carotene is biosynthesized from geranylgeranyl pyrophosphate. It is a member of the carotenes, which are tetraterpenes, synthesized biochemically from eight isoprene units and thus having 40 carbons. Among this general class of carotenes, β-carotene is distinguished by having beta-rings at both ends of the molecule. Absorption of β-carotene is enhanced if eaten with fats, as carotenes are fat soluble.

Carotene is the substance in carrots, pumpkins and sweet potatoes that colors them orange and is the most common form of carotene in plants. When used as a food coloring, it has the E number E160a.p119 The structure was deduced by Karrer et al. in 1930. In nature, β-carotene is a precursor (inactive form) to vitamin A via the action of beta-carotene 15,15'-monooxygenase. Isolation of β-carotene from fruits abundant in carotenoids is commonly done using column chromatography. The separation of β-carotene from the mixture of other carotenoids is based on the polarity of a compound. β-Carotene is a non-polar compound, so it is separated with a non-polar solvent such as hexane. Being highly conjugated, it is deeply colored, and as a hydrocarbon lacking functional groups, it is very lipophilic.

Medical uses
β-Carotene has been used to treat various disorders such as erythropoietic protoporphyria. It has also been used to reduce the risk of breast cancer in women before menopause, and the risk of age-related macular degeneration (AMD).

Cancer
Supplementation with β-carotene does not appear to decrease the risk cancer overall, nor specific cancers including: pancreatic, colorectal, prostate, breast, melanoma, or skin cancer generally. Evidence does not support a role for β-carotene in treating cancer.High levels of β-carotene may increase the risk of lung cancer in current and former smokers. Results are not clear for thyroid cancer.

Cataract
The effect of antioxidant vitamin supplementation on preventing and slowing the progression of age-related cataract has been studied. A Cochrane Review tested supplementation of β-carotene, Vitamin C, and Vitamin E, independently and combined on patients to examine differences in risk of cataract, cataract extraction, progression of cataract, and slowing the loss of visual acuity. However, these studies found no evidence of any protective effects afforded by β-carotene supplementation on preventing and slowing age-related cataract.