In vitro antioxidant and membrane stabilization activities of the fruit extract and fractions of Tetrapleura tetraptera (Schumach & Thonn.) Taub.
Arthritis is an inflammation of one or more joints. There is considerable experimental evidence linking lysosomal enzymes with tissue damage in arthritis. This study investigated anti-arthritic properties of Tetrapleura tetraptera (TT) using membrane stabilization assay (MSA). Powdered TT fruit sample was extracted by maceration in distilled methanol. Phytochemical screening was performed on powdered sample. The crude, partitioned extracts (n-hexane, chloroform and ethyl acetate) and seven pooled column chromatographic fractions were used for MSA (in vitro), using indomethacin and hypotonic solution as positive and negative controls. The total phenolic content (TPC) and antioxidant activity were determined. Phytochemical screening of TT showed the presence of important secondary metabolites. The ethyl acetate fraction showed the best protection of 98.77± 0.02% on red blood cells at 2.0 mg/mL. Fraction M at 0.5 mg/mL from EtOAC extract demonstrated significant (p<0.005) membrane stabilization activity (29.06±0.02%) compared to other pooled fractions (A, L, M, N, O, P, Q). The positive control, indomethacin, at 0.5 mg/mL, exhibited 56.02±0.02% membrane stabilization activity. The TPC ranged from 35.0-128.3 and 85.5 - 172.2 mg GAE/g for TT methanolic extract and pooled fractions, respectively. The IC50 values of the pooled fractions ranged from 41.16 ±0.02 to 91.56±0.04. Five compounds with different Rf values (0.58, 0.50, 0.62, 0.60, and 0.64) were isolated from the EtOAc fraction. The membrane stabilization activities demonstrated by the crude and ethyl acetate extracts and sub-fractions of Tetrapleura tetraptera may be attributed to antioxidant activities on the free radicals generated due to inflammatory reactions observed in most arthritic conditions.
Keywords: Tetrapleura tetraptera; Arthritis; Membrane stabilization activity; Anti-oxidant; Lysosomes