Correlation between total phenolic and mineral contents with antioxidant activity of eight Malaysian bananas (Musa sp.)

Correlations between total phenolic and mineral contents with antioxidant activities of pulps and peels from eight banana (Musa sp.) cultivars were studied. The total phenolic contents were determined using Folin-Ciocalteu colorimetric method, and antioxidant activities were measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and ferric reducing antioxidant potential (FRAP) assay. The highest total phenolic content (76.37 ± 1.79 mg GAE/g d.w.) was obtained from the freeze-dried extract of fresh pulps of Raja cultivar. The maximum activity of DPPH (19.39 ± 0.15 mg TE/g d.w.) was recorded for the chloroform extract of dried peels of Mas cultivar. Meanwhile, the highest activity of FRAP was shown by most of the chloroform extracts of dried pulps, dominated by Awak cultivar (22.57 ± 0.13 mg TE/g d.w.). With few exceptions, peel extracts exhibited higher total phenolic content and stronger antioxidant activities than that of the pulps. Very weak correlation between total phenolic content and FRAP activity was observed, yet it is higher (r² = 0.1614, p < 0.0001) than that of total phenolic content and DPPH activity (r² = 0.02339, p < 0.05). A moderate correlation between DPPH and FRAP activities was obtained (r² = 0.3533, p < 0.0001). For mineral analysis, potassium (K) is the major element found in both fresh pulps and peels followed by P, Mg and Na. Fresh peels of Raja consisted the highest amount of K (1387.5 mg/100 g f.w.). With exception of Mn, no correlation was found between mineral content and antioxidant activity. A moderate correlation between Mn content and DPPH activity was observed (r² = 0.2855, p < 0.0001).