Carotenoid Levels, Total Phenolic Content and Antioxidant Activity Variations in Varieties of Citrullus lanatus under Storage at Room Temperature

Introduction: Non-communicable diseases (NCDs) are economically burdening and are globally projected to increase deaths upto 75% by 2030. With the cause partly attributed to unhealthy diets, the major contributing factor is production of reactive oxygen and nitrogen species in biochemical reactions in human cells. Through a dietary approach, this can be countered by carotenoid and phenolic antioxidants in Citrullus lanatus (watermelon). The challenge presented is on the effect of room temperature (RT) storage on the levels of β- carotene, lutein and lycopene carotenoids and phenolics in watermelon. Varieties, of watermelon grown in Mwea, Kenya are reported for their carotenoid levels; antioxidant activity (AA) and total phenolic content (TPC) within 14 days storage period at RT.

Methods: The methods employed were HPLC, FCR and DPPH assay.

Results: The ranges of carotenoid levels were; β-carotene; 0.13±0.03- 3.15±0.02 μg/100 g, lutein; 10357.58±62.98-30573.99±434.40 μg/100 g and lycopene 113.42±0.39-522.76±1.36 μg/100 g. The AA ranged between 3.10±0.04-41.35±0.29 and 59.12±0.15- 79.93±0.18% in fresh and dried watermelons, while the TPC ranged between 266.00±5.00-896.67±7.37 mg/100 g GAE. The effect of storage on the nutritional values was shown by a general decrease on levels of β-carotene, lycopene, AA and TPC while lutein levels increased. There were significant differences (p<0.05) in measurements of carotenoids, AA and TPC between all sample varieties.

Conclusion: Storing watermelons for upto 14 days has both negative and positive implications on the carotenoid and total phenolic levels but clearly reduces the antioxidant activity and hence the effectiveness on the fight against NCDs.