Effect of Spacing and Maturity on Phenolic Phytochemical Composition of Umuspo1 and Ex-Onyunga Varieties of Orange Fleshed Sweet Potato at 12 and 16 Weeks

Abstract

This study examined phenolic phytochemical composition of two (2) Orange Fleshed Sweet Potatoes (OFSP) (<i>Ipomoea batatas</i>) varieties. The OFSP (Ex-Onyunga and Umuspo1) varieties were planted at different spacing 20 cm, 30 cm and 40 cm, respectively and harvested at 12 and 16 weeks. Flavonoid, Total polyphenol, Beta-carotene peels and Beta-carotene flesh contents were evaluated for Phenolic Phytochemical contents. Data generated were subjected to analysis of variance (ANOVA) using SPSS version 17. The flavonoid content of the Ex-Onyunga OFSP varieties planted at 20 cm, 30 cm and 40 cm at 12 weeks recorded the concentrations of 283.54 μg/g, 288.33 μg/g and 291.88 μg/g, respectively, and the Umuspo1 OFSP varieties planted at 20 cm, 30 cm and 40 cm at 12 weeks also recorded the concentrations of 263.13 μg/g, 268.33 μg/g and 275.21 μg/g, respectively. The flavonoid content of Umuspo1 OFSP varieties with the distance spacing of 20 cm, 30 cm and 40 cm had concentrations 268.54 μg/g, 270.00 μg/g and 276.25 μg/g, respectively, while Ex-Onyunga of OFSP varieties with the distance spacing of 20 cm, 30 cm and 40 cm had the concentrations of 260.63 μg/g, 226.25 μg/g and 248.54 μg/g, respectively. The total polyphenol content of Umuspo1 OFSP variety with the distance spacing of 40 cm had the highest value [41.99 μg/g], and significantly <i>[P<0.05]</i> different from the total polyphenol content of all other samples. There were significant (<I>P<0.05</I>) differences in the Beta-Carotene contents of flesh and peels. The Beta- carotene of flesh sample recorded values ranged from 184.31 μg/g + 0.93 μg/g to 335.47 μg/g + 1.69 μg/g at 12 weeks, and also recorded another values ranged from 189.11 μg/g + 2.17 μg/g to 216.97 μg/g + 0.28 μg/g at 16 weeks, while the Beta-carotene peels sample recorded values ranged from 323.67 μg/g + 9.17 μg/g to 386.39 μg/g + 3.85 μg/g at 12 weeks, and also recorded another values ranged from 336.11 μg/g + 7.90 μg/g to 347.16 μg/g + 2.00 μg/g at 16 weeks, respectively. The calculated retinol equivalent of two OFSP varieties [Umuspo1 and Ex-Onyunga] at different spacing distances enhanced results as <i>trans-β</i>-carotene of Umuspo1 and Ex-Onyunga OFSP recorded values ranged from 11.79<i> μ</i>g/g to 146.20 <i>μ</i>g/g. Among the samples analyzed, the Umuspo1 (US<sub>2</sub>) variety of OFSP planted at 30 cm exhibited the lowest concentrations of both carotenoids. Specifically, its 13-cis carotene content was 0.72 µg/g, while the 9-cis carotene content was 0.34 µg/g, both values being lower than those recorded for all other varieties and planting distances.