Mangosteen (Garcinia mangostana Linn.) belongs to the family Guttiferae. In the present study, crude methanolic mangosteen fruit rind extract was analyzed for its active constituents using thin layer Chromatography (TLC), Fourier transform infrared spectroscopy (FTIR) and Liquid chromatography–Mass spectrometry (LC–MS). Antioxidant potential of the extract was studied using: various biochemical assays, VERO & HELA cell lines, and animal models such as immuno-toxicity-induced albino mice, fishes. Larvicidal activity of the extract was also studied against the 3 and 4 instar larvae of the mosquito (Culex quinquefasciatus). TLC studies indicated the presence of 7 active fractions in the crude extract. FTIR analyses revealed the presence of aromatic Cdouble bond; length as m-dashC, C–O, –C–H (alkyl), and –OH as the main functional groups in all. LC–MS analysis revealed the presence of xanthones and other flavonoids. Total phenolic content was determined and found that the extract contained significantly large amount of phenolics: 5.95 ± 0.54 w/w of extract, which can be correlated to their antioxidant activities at three different concentrations such as, 30 mg (0.807 ± 1.05) 20 mg (0.612 ± 1.32) and 10 mg (0.425 ± 0.12) as the gallic acid equivalents. The extract showed a strong DPPH free radical-scavenging activity of 80.86 ± 1.79, nitric oxide (NO) scavenging of 37.47 ± 1.92, super oxide radical scavenging of 46.12 ± 1.66 and hydrogen peroxide scavenging at the mean value of 76.04%. The extract offered protection against adjuvant induced immunological injury by increasing the number of white blood cells, and by enhancing the antibody mediated protection by stimulating antibody production in albino rats. The extract has no significant effect on VERO cells whereas the HELA cells growth was affected at 15.0 μg/ml. The extract was significantly more effective for specific killing of cancer-type cell line (HeLa) compared to that of non-cancer-type cell line (Vero). The effects of dietary inclusion of various parts of mangosteen extracts on growth response and haematological parameters of African catfish (Clarias geriepinus) fingerlings showed that the extract has influenced the haematological parameters, but not the growth parameters. The extract was found effective against the 3 & 4th instar larvae of Culex quinquefasciatus. The structural deformation of siphon tube would probably led to their dysfunction, which may be intrinsically associated with the death of the larvae. Thus the popularly known queen of fruits is not only an edible entity but the waste part, i.e. the fleshy fruit rind can be a useful alternate for many bioprospects.