Comparative evaluation of organic and inorganic fertilizers on total phenolic, total flavonoid, antioxidant activity and cyanogenic glycosides in cassava (Manihot esculenta)

The study evaluated the effects of fertilizer sources and varieties on total phenolic, total flavonoid, antioxidant activities and cyanogenic glycosides of cassava leaves and tuber. The main factor was fertilizer sources (vermicompost, empty fruit bunch compost, NPK 15:15:15) and sub-factor was based on cassava varieties (Medan and Sri Pontian). Treatments were arranged in a split plot design with three replications. Phytochemical compounds and the antioxidant activities in young leaves and tuber were carried out after harvesting. Total phenolic and flavonoid compounds were determined by using Folin-Ciocalteu assay and aluminium chloride colorimetric method, respectively. The fertilizer sources and varieties were found to have significant effect on phytochemical compounds. Fertilizer and variety interaction was significant in total phenolics, total flavonoid, 1,1-diphenyl-2-picryl-hydrazyl (DDPH) scavenging assay and ferric reducing antioxidant capacity (FRAP) scavenging assay for tuber and leaves. The phenolic and flavonoid content was significantly higher (P<0.01) in the vermicompost treatments compared to mineral fertilizer and EFB compost. Medan had higher antioxidant activities as well as total content of phenolics and flavonoid in comparison with Sri Pontian. Organic fertilizer application resulted in significantly lower cyanide content compared to inorganic fertilizer. The results indicate that the fertilizer sources change phytochemical compounds of cassava tuber and leaves. Keywords : Manihot esculenta , cassava tuber, cassava leaves, fertilizer sources, phytochemical compounds, antioxidant activity African Journal of Biotechnology Vol. 12(18), pp. 2414-2421