Antioxidant and anti-inflammatory activities of durian (Durio zibethinus Murr.) pulp, seed and peel flour

The unripe pulp, inner peel and seed of durian were used in this study. These are generally not considered edible and must be disposed of as waste. However, they are good sources of bioactive compounds. Flour extracts from the unripe pulp, inner peel, and seed of two durian (Durio zibethinus Murr.) varieties, namely, Monthong and Chanee, were analyzed chemically to determine their total phenolic content (TPC), antioxidant, and anti-inflammatory capacities. Chanee pulp (CPu) contained a higher TPC (5285.37 ± 517.65 mg GAE/g) than Monthong pulp (MPu), Monthong peel (MP), Monthong seed (MS), Chanee peel (CP) and Chanee seed (CS) (p = 0.0027, 0.0042, 0.0229, 0.0069 and 0.36), respectively. The antioxidant activity of each durian extract was determined against ABTS, nitric oxide, superoxide, hydroxyl, and metal ions. The results indicated that the pulp, inner peel and seed of these durian varieties had antioxidant capacities. Murine Raw 264.7 macrophages were used to determine the cytotoxicity of the flour extracts. The extract of CS flour had the lowest cytotoxicity followed by MP, CPu, CP, MPu and MS (p = 0.5926, 0.44, 0.3191, 0.1471 and 0.0014), respectively. The anti-inflammatory activity was tested by anti-nitric oxide (NO) production in lipopolysaccharide (LPS) stimulated cells by co-treating the Raw 264.7 cells with each durian flour extract and LPS. The extract of MP flour had the lowest IC(50) against NO production, indicating the highest anti-NO production activity followed by CS, CPu, MPu, CP and MS (p = 0.7473, 0.0104, < 0.0001, 0.0002 and < 0.0001, respectively). The information obtained in this study is useful for researchers to explore more durian varieties in Southeast Asia to find bioactive compounds that might be novel nutraceuticals for antioxidant, anti-inflammation and therapeutic functional food.