21
The values with different letters a-v in each column show a significant differencep0.05 Figure 11 Caffeine content of coffee ground residue extracts
a
The amount of anthocyanin expressed as monomeric anthocyanin The values with different letters a-x in each column show a significant difference p0.05
Figure 12 Anthocyanin content of coffee ground residue extracts
D. Antioxidant Activity of Coffee Ground Residue CGR Extracts
Antioxidant is compounds which can delay, inhibit or prevent oxidation by scavenging free radicals and diminishing oxidative stress Dai et al., 2010. Phenolic compound has been
revealed to have antioxidant activity due to their hydroxyl and carboxyl group which able to bind metals Rice-Evans et al., 1997. Nowadays, numerous analytical methods developed to determine
in vitro antioxidant activity of plants, differ on how the compounds could have antioxidant activity against several reaction conditions.
u v
k n
fg c
fg ij
b s
t u
l m
hi ef
gh jk
c s
q p
d k
ef a
e fg
a r
q l
d hi
d a
e fg
a q
20 40
60 80
100 120
140 160
180 200
A B
C D
E F
G H
I j
Ca ff
ein e
m g
1 g
DB
Coffee Ground Residue Extract
3min 4min
5min Control
x w
r m
h j
f o
h v
v w
p n
k rp
de l
m s
t st
j ef
f op
f g
c i
q o
f j
d c
a h
b h
50 100
150 200
250 300
350
A B
C D
E F
G H
I J
An th
o cy
a n
in ยต
g 1
g DB
a
Coffee Ground Residue Extract
3 min 4 min
5 min Control
22
This work used two different analytical methods DPPH and FRAP to determine antioxidant activity in CGR extracts. DPPH assay could evaluate the ability of sample to scavenge
the DPPH free radical agent while the FRAP method could evaluate the reducing power of antioxidant agent by reduction of ferricyanide complex Fe
3+
to ferrous form Fe
2+
Pereira et al., 2007.
The antioxidant activity of the CGR extracts was shown in Figure 13. The CGR extracts had high antioxidant activity both as reducing agent and radical scavenging agent. Sample B 3
minutes had the highest antioxidant activity by 3.07 mmole TE100 g in DPPH assay and 5.31 mmole AAE100 g in FRAP assay, followed by B 4 minutes and A 4 minutes extracts,
respectively. The antioxidant activity of CGA extracts in this work were higher than those 2.04 mmol TE100 g ; isopropanol-water solvent by soxhlet extraction that reported by Murthy et al.,
2010.
The antioxidant activity determined by FRAP methods were higher than those in the DPPH methods. The results showed that the phenolic compounds in CGR extracts were mostly
acted as reducing iron. Iron is a primary cause of ROS reactive oxygen species generation in vivo because it plays such a role in contributing to oxidative stress, DNA damage, and cell death
Perron et al., 2009. The polyphenol ligands stabilize Fe
3+
unstabilized ions by converting into Fe
2+
ions and Fe
3+
- polyphenol complexes Chvatalova et al., 2008. The results also showed that the higher amount of bioactive compounds, the higher
antioxidant activity was obtained. The antioxidant activity of bioactive compounds contained in plants is related to their electron-donating activity, chelating metal activity and peroxidase activity
Michalak, 2005. Phenolic compounds such as chlorogenic acid and anthocyanin have some aromatic rings and OH-group in their structures. The free OH-group would bind the free radical
chain oxidation produced by lipid hydroperoxide LOOH then released stable radical ions Millic et al., 1998. Caffeine is an alkaloid group that also has aromatic rings and free OH-groups.
Caffeine extracted from coffee has shown a significant decrease of MDA levels in the rat livers Demirtas, 2011. The hydroxyl group in caffeine could suppress the superoxide and chelate the
metal ions Lee, 2011.
The high amount of bioactive compounds and antioxidant activity in the three CGR extracts would be strong evidences to apply the extracts as antimicrobial activity against several
pathogens in the next part of this work.
a
The antioxidant activity expressed as trolox equivalent for DPPH and ascorbic acid equivalent for FRAP
The values with different letters a-c in each column show a significant differencep0.05 Figure 13 Antioxidant activity of CGR extracts
a a
c c
b b
0.5 1
1.5 2
2.5 3
3.5 4
4.5 5
5.5
DPPH FRAP
Ant io
x ida
nt m
m o
le1 g
a
Antioxidant activity methods
A 4 min B 3 min
B 4 min
23
D. Antimicrobial Activity of Coffee Ground Residue Extract
