Total Phenolic Content, Antioxidant and Antibacterial Activities of Different Fractions of Sonneratia apetala (Buch.-Ham.) Fruit

Abstract

Plants are the most important source of bioactive compounds providing health benefits. The mangrove fruit Sonneratia apetala (Buch.-Ham.) is extensively consumed by the people of coastal Bangladesh especially adjacent to the Sundarbans’ forest. To seek out the potential source of bioactive compounds, free radical scavenging activity, antioxidant capacity and antibacterial activities, different fractions of S. apatala (Buch.-Ham.) fruit (seed and pericarp) were studied. The solvents used for the fractionation were n-hexane, di-ethylether, chloroform, ethylacetate and methanol. Among the fractions, methanol (MS) extract of seed had the highest polyphenols (221.95 mg GAE/g extract) content followed by di-ethylether (DS; 33.35 mg GAE/g) and ethylacetate (ES; 29.36 mg GAE/g) extracts of seed whether methanol (MP) extract of pericarp had the lowest polyphenols (10.31 mg GAE/g) content. From the experiment it was seen that MS showed the most potent DPPH radical scavenging activity with an IC₅₀ value 4.38 μg/mL followed by ES (30.37 μg/mL) and DS (38.23 μg/mL). MS showed 51.77 % NO radical scavenging activity at 800 μg/mL with an IC₅₀ value 415.20 μg/mL followed by DS and MP with IC₅₀ values of 1431 and 2030.46 μg/mL respectively. At 100 μg/mL, MS showed the highest absorbance (O.D. 1.672) followed by ES (O.D. 0.346) and DS (O.D. 0.321). At 200 μg/mL, chloroform (CS) extract of seed showed the highest metal (Fe²⁺) binding capacity (48.67 %) followed by MS (42.67 %) and hexane (HS; 40.13 %) extracts of seed. The IC₅₀ values for CS, MS and HS in chelating Fe²⁺ were 296.38, 498.01 and 396.83 μg/mL respectively. Moreover, MS showed the highest total antioxidant capacity (183.34 mg AAE/g; 121.42 mg GAE/g). This was followed by DS (177.11 mg AAE/g; 117.31 mg GAE/g) and CS (156.37 mg AAE/g; 103.56 mg GAE/g). Total antioxidant capacity was lowest in di-ethylether (DP) extract of pericarp (13.54 mg AAE/g; 8.96 mg GAE/g). In addition, MS inhibited the growth of Escherichia coli, Salmonella paratyphi A, Salmonella typhi, Shigella dysenteriae and CS inhibited the growth of Vibrio cholera, whereas both of them inhibited the growth of Staphylococcus aureus. The IC₅₀ values for MS against E. coli, S. paratyphi A, S. typhi, S. dysenteriae and S. aureus were 0.56 mg/mL, 0.2632 mg/mL, 1.8632 mg/mL, 0.847 mg/mL and 1.0186 mg/mL respectively whether that for CS against S. aureus and V. cholera were 1.33 mg/mL and 1.02 mg/mL respectively. MS completely inhibited the growth of E. coli, S. paratyphi A and S. dysenteriae at 2, 1 and 2 mg/mL respectively. In conclusion, the results showed that among the fractions MS, DS and CS are potential sources ofbioactive compounds such as polyphenols, antioxidants, whereas MS and CS have potential antibacterial activities. Therefore the fruits of S. apetala have activities beneficial to health.