Quantification of lycopene and its analogues in different varieties of papaya grown in Tharaka Nithi County
Muthui, Gerald Gitonga
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Carotenoids are a group of naturally occurring phytochemicals, many of which are important in human nutrition and health. In particular, lycopene and its analogues may have potent antioxidant properties to protect cells and tissues from oxidative stress and free radicals, and thus contribute to enhancement of immune functions of the body. These antioxidants may also prevent damage to cells and DNA, as well as stimulate the repair of oxidative damage to DNA. Diets rich in these phytochemicals appear in some studies to lower risk of certain types of cancer, especially cancers of the prostate, lung and stomach, as well as cardiovascular diseases and age-related eye disorders. Previous studies have shown that papaya has moderate levels of lycopene and its analogues. Different varieties of papaya are commonly grown in Kenya but there exist no data on levels of the different carotenoids at different ripening stages of these varieties. Four varieties of papaya from Tharaka Nithi County referred to as export, mountain, SP and local were studied. Lycopene and two analogues, β-carotene and β-cryptoxanthin, were analysed using reverse phase isocratic HPLC system with UV detector. Two levels of ripening stages were studied: first ripening stage was seven days after papaya was harvested and kept at 25.3 ± 0.9ºC temperature and 70.5 ± 4.7% relative humidity; and second ripening stage was six days later. The results showed that there was significant difference between the levels of lycopene from the first ripening stage to the second one in export and SP variety, while there was no significance difference in local and mountain variety. There was significant difference in β- cryptoxanthin between the ripening stages for local, SP and mountain varieties while there was no significance in export variety. For β-carotene significant difference between the ripening stages was only seen in the local variety. The highest level in second ripening stage for lycopene was in export variety with 2.62±0.07 mg/100g and least in mountain variety with 0.84±0.07 mg/100g. β-Carotene level was highest in the local variety (1.293±0.21 mg/100g) and lowest in the SP (0.601±0.04 mg/100g) while β-cryptoxanthin was highest in SP variety (7.03±0.10 mg/100g) and least in the export variety (2.32±0.07 mg/100g). This study shows that there is significantly high levels of carotenoids in the four varieties of papaya. These high levels can be exploited through consumption of different varieties of papaya which can aid in lowering the risks of different types of cancers and cardiovascular diseases There is need to study other carotenoids especially xanthophylls (lutein and zeaxanthin) in different varieties of papaya and observe how agro-ecological zones affects the levels of these carotenoids. Quality controlled processing and storage of papaya pulp during peak seasons should be used to reduce losses during peak seasons.