Antioxidant activity, phenolics and UPLC–ESI(–)–MS of extracts from different tropical fruits parts and processed peels

• Fruit peels and seeds presented higher antioxidant capacity than their respective pulps.
• Fruit byproducts presented higher antioxidant compounds than their respective pulps.
• PCA showed that oven drying and freeze drying affected antioxidant capacity and organic acid composition of fruit peels.
• Catechin, epicatechin gallate, epicatechin, epigallocatechin, and epigallocatechin gallate were quantified on a few fruits.
• Avocado dried peel and passion fruit seed are good antioxidant natural source.

The antioxidant capacities of avocado, pineapple, banana, papaya, passion fruit, watermelon and melon's different parts (pulp, seed, raw peel and dried peels) were evaluated using DPPH and FRAP assays. Levels of total phenolic compounds and flavonoids were measured. Quantitation of organic acids (citric, malic and tartaric) and phenolic compounds was also performed by UPLC–ESI(−)–MS. Avocado dried peel presented the highest total phenolic compounds (1252.31 ± 165.62 mg GAE 100 g− 1 DW), the highest antioxidant capacities by the FRAP assay (441.83 ± 67.86 μmol FeSO4 g− 1 DW) and the lowest IC50 value (18.22 ± 1.45 μg·mL− 1), followed by passion fruit seed (49.71 ± 2.17 μg·mL− 1). Melon raw peel presented the highest total flavonoids (204.28 ± 21.05 mg EQ 100g− 1 DW). Citric, malic and tartaric acids as well as catechin hydrate, epicatechingallate, epicatechin, epigallocatechin, and epigallocatechin gallate were found in the methanol fruit extracts by UPLC–ESI–(−)–MS.