Correlation between total phenolics and mineral content with antioxidant activity and determination of bioactive compounds in various local bananas (musa sp.)
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Date
2008
Authors
Md Yusoff, Nor Adlin
Journal Title
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Abstract
This study was designated to evaluate the correlation between total phenolics and mineral
content with antioxidant activity in various extracts of pulps and peels of eight local banana
cultivars, Musa sp. In addition, identification and characterization of the bioactive compounds was
also carried out. Samples were extracted using three different extraction procedures. The total
phenolic contents were measured by Folin - Ciocalteu colorimetric method, whereas antioxidant
activity was estimated by using 2, 2- diphenyl- I - picrylhydrazyl (DPPH) free radical scavenging
assay. These extracts exhibited a wide range of total phenolic content and antioxidant activity
varying from I2.47 ± O.I2 to I75.47 ± 0.31 mgGAE/g dry extract and IO.I2 ± 0.64% to 80.04 ±
0.66%, respectively at 2000 Jlg/ml concentration. Generally, peel extracts exhibited higher total
phenolic content and stronger antioxidant activity than pulp extracts. Among all extracts, the dried
banana samples extracted with various solvent polarities using Soxhlet apparatus showed the
highest total phenolic content and the most potent antioxidant activity. Significant and positive
linear correlation were found between total phenolic content and antioxidant activity (r2
= 0.6073, p
< 0.000 I), indicating that phenolics were the major antioxidant constituents in the extracts.
Meanwhile, the Rr values and colour on thin layer chromatography plates developed by various
solvent systems, mass spectral and ultraviolet spectrum were used to identity and characterize the
bioactive compounds. A total two bioactive phenolic compounds were identified, which were 3, 5, 8
droxymyricetin and ferulic acid. Total phenolic content of both bioactivc
compounds were 395.07 ± 0.12 mg GAEl g dry extract and 175.87 ± 0.12 mg GAEl g dry extract,
respectively. Meanwhile, the percentage of antioxidant activity were 86.15 ± 0.05% (3, 5, 8 -
trimethyl 6, 8 dihydromyricetin) and 27.42 ± 1.16% (ferulic acid). The presence of these
compounds in the banana peels has never been reported. The content of macrominerals (Na, K, Ca
and Mg) and microminerals (Fe, Cu, Zn and Cu) in local bananas has been determined by atomic
absorption spectrometer (AAS) and atomic emission spectrometer (AES). Potassium was the most
significant mineral element presents in both banana pulps and peels with an estimated value of
295.68-463.57 mg/1 00 g fresh weight and I 071.20- 1361.56 mg/1 00 g fresh weight, respectively.
Based on the obtained results, bananas are shown to contribute to the recommended daily
requirements suggested by US - RDA for K, Mg, Fe and Zn. Overall, the relative order of
concentration of macrominerals both in pulps and peels was K > Mg > Na > Ca, while the decrease
order of microminerals concentration was Mn > Fe > Zn > Cu. In addition, mineral content was
found as not significantly correlate with their antioxidant activity with the exception of K and Mn
which form a moderate correlation with antioxidant activity of water extracts.
Description
Keywords
Total phenolics , Antioxidant activity , Various local bananas (musa sp.)