Carotenoids are natural pigments synthesized by plants and photosynthetic microorganisms, some of which, like β-carotene, are precursors of vitamin A, and others such as lutein and lycopene might function in the prevention of age-related macular degeneration and prostate cancer, respectively. Mass spectrometry provides high sensitivity and selectivity for the identification and quantitative analysis of carotenoids in biological samples, and previous studies have described how atmospheric pressure chemical ionization (APCI) offers distinct advantages over electrospray and fast atom bombardment for the analysis of specific carotenoids. Since APCI product ion tandem mass spectra have been reported for only a few carotenoids, a detailed investigation of twelve carotenes and xanthophylls was carried out using both positive ion and negative ion APCI tandem mass spectrometry with collision-induced dissociation. Using protonated molecules as precursor ions in positive ion mode and radical anions in negative ion mode, characteristic fragment ions were identified that may be used to distinguish between carotenoids.

An acyclic, non-provitamin A carotene, lycopene is responsible for the red pigmentation of ripe tomatoes and some other edible fruits such as watermelon and papaya. Lycopene is also a potent antioxidant and scavenger of free radicals. Multiple retrospective and prospective epidemiological studies have indicated that the consumption of tomato products containing lycopene is associated with a reduced risk of prostate cancer. These epidemiological studies are supported by numerous in vitro assays using cell cultures that show anti-cancer activities and cancer chemoprevention activities of lycopene in many cell lines including prostate cancer cells. These activities include inducing apoptosis, inhibiting metastasis, preventing oxidative stress, and up-regulating the antioxidant response element so that cells can produce cytoprotective enzymes against prooxidants and electrophiles. In vivo animal studies and Phase I and II clinical trials have shown that lycopene supplements are non-toxic and that lycopene is orally bioavailable. Furthermore, lycopene is concentrated in prostate tissue and localized to the nucleus. In addition, some oxygenated metabolites of lycopene have been identified, and might be active as chemoprevention agents. The next phase of research concerning lycopene as a chemoprevention agent will be Phase II clinical trials of efficacy that are placebo-controlled, randomized and double blind. These clinical trials are required to establish the efficacy of lycopene supplementation.

Consumption of tomato products is associated with a decreased risk of prostate cancer, and lycopene, the red carotenoid in the tomato, is a potent antioxidant that might contribute to this chemoprevention activity. A double-blind, randomized, placebo-controlled trial of 105 African American men veterans, recommended for prostate biopsy to detect cancer was carried out to investigate whether oral administration of lycopene increases lycopene levels in blood and prostate tissue and lowers markers of oxidative stress. Urology patients were randomly assigned to receive 30 mg/d of lycopene as a tomato oleoresin or placebo for 21-days prior to prostate biopsy for possible diagnosis of prostate cancer. A total of 47 men were diagnosed with prostate cancer and 58 were diagnosed with benign prostate hyperplasia. Diet, smoking, and drinking habits were assessed. For the men receiving lycopene, the mean lycopene concentration increased from 0.74 ± 0.39 to 1.43 ± 0.61 μmol/L in plasma (P <0.0001) and from 0.45 ± 0.53 to 0.59 ± 0.47 pmol/mg in prostate tissue (P = 0.005). No significant changes in the DNA oxidation product 8-oxo-deoxyguanosine or the lipid peroxidation product malondialdehyde were observed in prostate tissue or plasma, respectively, as a result of lycopene administration.