Abstract
ABSTRACT
Antioxidants which reduce the risks of the incidence of neurogenerative diseases are contained in vegetables. The nutritional contents of vegetable as well as the concentrations of these antioxidants are affected by soil nutrient compositions. A pot experiment was carried out to evaluate the influence of Craseonycteris thonglongyai (hog-nosed bat) compost and a conventional synthetic fertilizer on the antioxidant constituents in the leaves of Hibiscus sabdariffa. The antioxidants assessed include lycopene, β-carotene, carotenoid, tocopherol, ascorbic acid and chlorophyll. The leaves of H. sabdariffa were harvested at vegetative phase and the concentrations of tocopherol, lycopene, chlorophyll, β-carotene and total carotenoid were determined by spectrophotometric method while ascorbic acid content was analysed by titrimetric method. Results showed that the concentrations of chlorophyll and β-carotene in H. sabdariffa increased significantly (p < 0.05) with applied C. thonglongyai compost whereas synthetic fertilizer had no significant effect on these parameters. Similarly, treatment with both synthetic fertilizer and C. thonglongyai compost significantly (p < 0.05) increased the carotenoid, tocopherol and lycopene contents H. sabdariffa, however, the lycopene content in the vegetable fertilized with the compost was significantly (p < 0.05) higher compared with those fertilized with synthetic fertilizer. While C. thonglongyai compost had no significant effect on the concentration of ascorbic acid in the H. sabdariffa its content decreased significantly (p < 0.05) with the application of synthetic fertilizer. The study concludes that both synthetic fertilizer and C. thonglongyai compost enhance the bioaccumulation of antioxidants in H. sabdariffa with C. thonglongyai compost been the preferred manure as it increases the concentrations of most of the antioxidants in the vegetable more than synthetic fertilizer.

Keywords: leafy vegetables, antioxidants, Hog-nosed bat compost, synthetic fertilizer, Hibiscus sabdariffa

Key words: Keywords: leafy vegetables, antioxidants, Hog-nosed bat compost, synthetic fertilizer, Hibiscus sabdariffa