Antioxidant compounds and activity in cucumber fruit in response to foliar and soil humic acid application

Abstract

Humic acid (HA), with its hormon-like activity influences yield and quality of fruits and vegetables. This study was performed to determine the influence of foliar and soil HA fertilization on antioxidant properties of cucumber fruit. Cucumber plants were treated with soil and foliar HA at various concentrations (0 mL L -1, 10 mL L -1, 20 mL L -1, 30 mL L -1 and 40 mL L -1) via spraying or drenching to the plant root area. Fruits were harvested at commercial maturity and their antioxidant activities in the hydrophilic (HAA) and lipophilic (LAA) fractions, lycopene, beta carotene, xanthophylls, total phenolics and chlorogenic acid contents were determined. The results demonstrated that HA application significantly improved both HAA and LAA activities in cucumber fruit. Moreover, HA also significantly enhanced total carotenes and xanthophylls, beta carotene, lycopene and chlorogenic acid contents. The data suggested that HA could be used to significantly improve cucumber fruit quality by enhancing its content of antioxidant compounds.