Valorization of seed and kernel marcs and evaluation of their antioxidant potential

The processing and consumption of mango (Mangifera indica) generate a sizeable amount of kernel waste with enormous and largely unexplored potential, while by-products from njangsa (Ricinodendron heudelotii) seed and bush mango (Irvingia gabonensis) kernel oil extraction are often discarded. This study aims to repurpose these kernels and seed wastes into added/high-value products and evaluate the ethanolic and methanolic extracts of their pressed marcs for polyphenolic content and potential antioxidant activity. The total phenolic content (TPC) and total flavonoid content (TFC) in the marc extracts ranged between 47.87 and 376.0 mg GAE/g and 4.85 and 13.70 mg Rutin/g, respectively. Both mango kernel marc extracts showed higher potent reducing power, ABTṠ⁺ radical and DPPḢ radical scavenging activities with half effective concentration (EC₅₀) values (0.20-0.22 mg/mL) comparable to the reference compound; ascorbic acid (0.20 mg/mL). The TPC and TFC of the marc extracts generally strongly correlated with antioxidant activity. Relatively higher contents of xanthophyll and β-carotene were detected in bush mango kernel methanolic extract than in the other extracts. Extraction solvent affected the composition and content of bioactives in pressed marcs of njangsa seed and mango kernel.