Abstract:
Coconut cake (CC) is the by-product of coconut oil manufacturing process which is
rich in antioxidants. There is very little information on the antioxidant activity of CC
in biological systems. In this study, the correlation of antioxidant activity of CC with
biological and chemical systems was monitored. Ethanol: water 70: 30 (v/v) was used
to extract phenolic compounds and that extract is denoted as CCPE. The total phenolic
content was 1892±51 GAE mg/kg dry weight and o-diphenol content was 591±48
CAE/kg dry weight. The percentage of ferric reducing power and DPPH radical
scavenging activity of CCPE increased with increasing concentrations. Those
antioxidant activities are comparable to gallic acid (GA). HPLC system was used to
identify and quantify the total polyphenols present in CCPE. GA is the prominent
polyphenol compound while syringic acid is the least abundant. The effect of CCPE
on deoxyribose degradation and protein carbonylation showed comparable antioxidant
activity to GA. Further, CCPE has the ability to prevent DNA damage in -vitro. HEp-
2 human epithelial cells were used as the biological system to measure the antioxidant
activity of CCPE. CCPE significantly (P≤0.05) inhibited MDA formation, protein
carbonyl formation and mt-DNA damage in HEp-2 cells. The amount of oxidized
glutathione decreased resulting in a significantly (P≤0.05) increased GSH/GSSG ratio
upon treatment with CCPE. Further, CCPE resulted in no significant change in GPx
expression compared to the unstressed cells. Therefore, CCPE can inhibit oxidative
stress-induced macromolecular damage on carbohydrate, protein, lipid and DNA in
both chemical and biological systems and the protective effect does not appear to result
from a change in the level of expression in the oxidative stress response genes.
