Mangifera indica Linn popularly known as mango is used in folk medicine to treat gastrointestinal disorders. The aim of this study was to identify the metabolomic composition of lyophilized extract of mango leaf (MIE), to evaluate the antioxidant activity on several oxidative stress systems (DPPH, FRAP, TBARS, and ABTS), the spasmolytic and antispasmodic activity, and intestinal protective effect on oxidative stress induced by H2O2 in rat ileum. Twenty-nine metabolites were identified and characterized based on their ultra-high-performance liquid chromatography (UHPLC) high-resolution orbitrap mass spectrometry, these include: benzophenone derivatives, xanthones, phenolic acids, fatty acids, flavonoids and procyanidins. Extract demonstrated a high antioxidant activity in in-vitro assays. MIE relaxed (p < 0.001) intestinal segments of rat pre-contracted with acetylcholine (ACh) (10−5 M). Pre-incubation of intestinal segments with 100 µg/mL MIE significantly reduced (p < 0.001) the contraction to H2O2. Similar effects were observed with mangiferin and quercetin (10−5 M; p < 0.05) but not for gallic acid. Chronic treatment of rats with MIE (50 mg/kg) for 28 days significantly reduced (p < 0.001) the H2O2-induced contractions. MIE exhibited a strong antioxidant activity, spasmolytic and antispasmodic activity, which could contribute to its use as an alternative for the management of several intestinal diseases related to oxidative stress.