Notulae Scientia Biologicae (Jun 2022)
Comparative studies of antioxidants and amino-acids concentrations in the fruits of two cultivars of watermelon (Citrullus lanatus L.)
Abstract
Importance of fruits and vegetables in diet and health cannot be overemphasized. Cultivation practices can however influence the nutritional compositions of fruits and vegetables. Hence, field and laboratory experiments were carried out to determine and compare the antioxidants and amino-acids concentrations of a hybrid and an indigenous cultivar of watermelon in Osun State University, Teaching and Research Farm, Nigeria. Influence of NPK 15:15:15 fertilizer at different rates (0, 100, 200 and 300 kg/ha) was evaluated on ‘Kaolack’ (hybrid) and ‘Rothmas’ (local) cultivars of watermelon. 200 kg/ha of the fertilizer was found to bring out the optimal yield of both cultivars. Hence, at 0 kg/ha and 200 kg/ha, mature fruits of the cultivars were analyzed for the antioxidants and amino-acids using standard analytical methods. Antioxidant properties of ‘Rothmas’ were found to be significantly (P≤0.05) higher than those of ‘Kaolack’ with the exception of the radical scavenging ability and lycopene content of ‘Kaolack’. Fruits that received no fertilizer across the cultivars exhibited more antioxidant potency compared to fruits under 200 kg. Results of amino acids concentration showed that, threonine, serine, glutamic-acid, alanine, valine, phenylalanine and arginine in ‘Rothmas’ were significantly higher compared to the contents in ‘Kaolack’. Except for tryptophan, alanine, lysine and phenylanine, fruits that received no fertilizer had higher contents of amino acids. Where fertilizer is needed to boost soil fertility, 100 kg/ha of NPK is recommended, this can be augmented with the organic nutrient or green manure if necessary, depending on the available nutrients in the soil before cultivation. This is very critical so as not to compromise the health-giving substances in the fruits. Local landraces of fruits and vegetables obviously have to be brought into limelight through research.
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