Effect of different harvesting times on phytochemical constituents and antioxidant activity of Jatropha zeyheri leaves

Abstract

Tea harvesting time is one of the key factors which influence the physiological, physical and chemical qualities of tea. However, the influence of harvesting times on phytochemical constituents and antioxidant activity of Jatropha zeyheri indigenous tea has not been documented. Therefore, the objective of this study was to evaluate the effect of harvesting times on phytochemical constituents and antioxidant activity in J. zeyheri leaves. Jatropha zeyheri leaves were harvested at Khureng village, Lepelle-Nkumpi Municipality, in Limpopo Province South Africa. Five treatments constituting February, March, April, May and June were arranged in a randomised complete block design, with 10 replications. Leaves were harvested monthly and oven-dried for 24 hrs at a temperature of 60°C. The dried leaves were ground through 1 mm sieve using grinder prior analysis. After laboratory preparations, phytochemicals and antioxidant activity were analysed using the UV-visible spectrophotometer. Data were subjected to ANOVA using the Statistix 10.0 and mean separation achieved using LSD Test. Harvesting times had highly significant effects on the antioxidant activity, total phenol and flavonoid contents contributing 62, 88 and 60%, respectively, in total treatment variation, but was non-significant on tannins. Antioxidant activity, total phenol and total flavonoid contents over increasing harvesting times exhibited quadratic relations, which were explained by 50, 87 and 95%, respectively. Relative to harvesting in February, harvesting times decreased antioxidant activity and total phenol contents by 10-28 and 29-52%, respectively, whereas total flavonoid contents were increased by 2-137%. In conclusion, antioxidant activity, total phenol and flavonoid contents were affected by harvesting times.