The present work aims to study the phytochemical composition, the antioxidant capacity of the crude extracts, and the fraction of extract giving the best antioxidant activity of Avicennia marina. The leaves contain high TFC compared to other parts of the plant, whereas fruits have the highest amount of TPC. Fat-soluble pigments are strongly present in the leaves of Avicennia marina i.e. beta-carotene, lycopene, chlorophyll a, and chlorophyll b. The crude methanolic flower extracts showed strong DPPH and ABTS radical scavenging activity with IC50 values of 0.30 and 0.33 mg/mL respectively compared to the leaf and stem methanolic extracts for the DPPH and ABTS models with a value IC50 greater than 1 mg/mL. The crude fruit extract shows good activity with the ABTS model, unlike the DPPH model whose IC50 values are 0.95 and 0.38 mg/mL, respectively. Fractionation improved the antioxidant effect of crude flower extract. The ethyl acetate fraction exhibits the best antioxidant activity for both DPPH and ABTS methods with IC50 values of 0.125 and 0.16 mg/mL. The HR-LCMS/MS led to the identification of 13 compounds: 6 flavonoids and 7 iridoid glycoside compounds in the different parts of the plant. A bioinformatics study was performed to evaluate the antioxidant activity of the three major Iridoid glycosides towards the target protein Catalase compound II through free binding energy. Out of these three iridoid glycosides, compound C10 does not represent any toxicity, unlike C8 and C9 which showed an irritancy effect. Furthermore, molecular dynamics shows good stability of the C10-2CAG complex.Communicated by Ramaswamy H. Sarma