Abstract:
Soursop fruit contains various bioactive compounds and has been used as valuable fruit in Sri
Lanka. Different maturity stages and extraction method used could affect antioxidant activity of
fruits. Therefore, present study investigated antioxidant activity of soursop at four different
maturity stages (unripe stage (UR), harvesting stage 1 (HS1), harvesting stage 2 (HS2), and well ripened stage (WR) extracted using two extraction methods. Sonication and stir plate were used
as extraction techniques while absolute ethanol and 70% (v/v) ethanol were used as extraction
solvents. The analyses of antioxidant activity conducted were Total Phenolic Content (TPC), Ferric
Reducing Antioxidant Power (FRAP), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) Radical
Scavenging Activity. From the analyses, the TPC, FRAP assay and DPPH activity was significantly
(p<0.05) changed with maturity stages. The highest TPC (165.67±2.86 mg GAE g-1) was identified
in 70% ethanol extract of WR stage with sonication extraction method. The highest (p<0.05) FRAP
(393.91±4.23 µmol Fe+2 L-1) value was identified in 70% ethanol extracts of HS2 with sonication
extraction. The highest DPPH activity (IC50-60.13±0.18 ppm) was identified in 70% ethanol
extract of WR stage with sonication extraction. The content of all the antioxidant compounds by
three different assays increased (p<0.05) as maturity progressed. Hence, it can be concluded that
soursop extracted using 70% ethanol extract of WR stage with sonication extraction method had
powerful phenolic content, 70% ethanol extracts of HS2 with sonication extraction had powerful
FRAP values and 70% ethanol extract of WR stage with sonication extraction had powerful IC50
values, suggesting their potential applications as health promoting functional ingredients.