Screening Carotenoid Content in Seeded and Seedless Watermelon Fruit

Abstract

Watermelons contain the carotenoids b-carotene, phytofluene, lycopene, and lutein. These carotenoids play an important role in plant oxidative protection and may serve to protect humans against oxidative assaults. Of the carotenoids, lycopene is the predominant pigment in red-fleshed melons (30-130 μg·g-1), b-carotene is present in small amounts (1-14 μg·g-1), and other carotenoids are present in minute amounts (1-3 μg·g-1). Seventy varieties were screened for lycopene content using scanning colorimetry, spectrophotometry, and HPLC techniques, and grouped as low, medium, high, or very high in lycopene. Pink-fleshed heirloom varieties such as Sweet Princess and Black Diamond contained low amounts of lycopene (<40 μg·g-1). A number of seeded and seedless varieties had medium amounts of lycopene (40-60 μg·g-1). Varieties in the high category (60-80 μg·g-1) were primarily seedless types, although `Dixie Lee', an open-pollinated, seeded variety had 69 μg·g-1, indicating that high lycopene content is not restricted to hybrid or seedless melon germplasm. Six selections were found to be very high in lycopene (>80 μg·g-1), including the minimelon Hazera 6008 (Extazy). Total carotenoids and carotenoid profiles were determined by HPLC for 23 varieties in 2003. Both seeded and seedless type melons had varieties high in bcarotene, lycopene, and total carotenoids. These results indicate that commercial watermelon varieties have a wide range in lycopene and b-carotene content, and that most commercially important varieties are high in lycopene and total carotenoids, providing important sources of phytonutrients to the human diet.