In vitro and ex vivo antihydroxyl radical activity of green and roasted coffee

The specific antiradical activity against the hydroxyl radical of the water soluble components in green
and dark roasted Coffea arabica and Coffea robusta coffee samples, both in vitro by the chemical
deoxiribose assay and ex vivo in a biological cellular system (IMR32 cells), were determined. All the
tested coffee solutions showed remarkable antiradical activity. In the deoxiribose assay, all the tested
solutions showed similar inhibitory activity (IA%) against the sugar degradation (IA values ranged
from 45.2 to 46.9%). In the cell cultures, the survival increase (SI%) ranged from 197.0 to 394.0%
with C. robusta roasted coffee being significantly more active than the other samples. The coffee
solutions underwent dialysis (3500 Da cutoff membrane) to fraction their components. In both systems,
the dialysates (MW < 3500 Da) either from green or roasted coffee, showed antiradical activity, while
the only retentates (MW > 3500 Da) from the roasted coffee samples were active. The preparative
gel-filtration chromatography of roasted coffee C. robusta dialysate gave three fractions active in the
biological system, all containing chlorogenic acid derivatives. The most active fraction was found to
be that containing the 5-O-caffeoilquinic acid, which shows a linear relation dose-response ranging
from 0.02 to 0.10 mM. The results show that both green and roasted coffee possess antiradical
activity, that their more active component is 5-O-caffeoyl-quinic acid, and moreover that roasting
process induces high MW components (later Maillard reaction products, i.e., melanoidins), also
possessing antiradical activity in coffee. These results could explain the neuroprotective effects found
for coffee consumption in recent epidemiological studies.