Antimicrobial activity of P. granatum methanolic extract
constituent of P. granatum
responsible for antimicrobial activity are phenolic compound including
pelargonidin-3-galactose, cyanidin-3-glucose, gallic acid, quercetin and
myricetin (15). It is also has been reported that antimicrobial activity is
related to flavonoids compound which is a class of phenolic compound (6).
Phenolic compound is a polar compound due to its abundance of polar hydroxyl
group. Since the solvent used for extraction of P. granatum peel is methanol ie polar solvent, phenolic compounds
contained in the peel are able to be dissolved in the methanol. Thus,
methanolic extract of P. granatum
containing phenolic compounds is thought to be responsible for antimicrobial
it is observed that the antibacterial activity exhibited by P. granatum is considerably lower than
the ones previously reported (2, 16, 19).The main reason for the low
antibacterial of P. granatum extract
in this study could be due to the fact that the pomegranate fruit used in the
previous study was locally-sourced in comparison to imported pomegranate fruit
which were used in this study. There is difference in total phenolic content
(TPC) of local and imported pomegranates. TPC of local and imported pomegranate
had been compared and found that, extract of local P. granatum (4.8 GAE mg/g plant extract) has a significantly higher
TPC than the extract of imported P.
granatum (3.8 GAE mg/g plant extract) (9).
study on the effect of different storage temperature (22°C, 10°C, °C and 5°C)
for 16 weeks on TPC of pomegranate fruit showed that the TPC was significantly
reduced with longer storage (7). After 16 weeks of storage, all fruits decayed
except for fruits stored at 7°C and 5°C. Although storage at low temperature
can prevent decay of fruit, storage at low temperature reduced the total
phenolic content in fruit especially when stored at 5°C. So, storage at low
temperature can also be the factor that cause TPC of imported pomegranate lower
than the local ones. Interestingly, the handpicked local pomegranates contained
higher TPC due to shorter storage period (9). These two factors could explain
the lower TPC of imported pomegranate.
study claimed that phenolic compound is the active constituent which
responsible for antibacterial activity of P.
granatum extract including pelargonidin-3-galactose, cyanidin-3-glucose,
gallic acid, quercetin and myricetin (15). Besides, antimicrobial activity is
also related to the presence of flavonoid which is a phenolic compound (6).
pomegranate used in the studies by Ahmet et
al (2009), Saad et al (2010) and Naziri et al
(2012) were claimed to be local fruits. So the TPC in the fruits used in the
previous study should be higher when compared to imported pomegranate fruit
used in the current study. Due to high TPC, antibacterial activity P. granatum extract in the previous
study is more superior compared to the antibacterial activity of P. granatum extract in the current
to Figure 1, P. granatum extract did
not show any activity against C. albicans.
This could be due to the fact that the grade of pomegranate cultivars used in
the study has no antifungal activity. A previous study conducted by Ahmet et al (2009) evaluated antimicrobial
activity of six different P. granatum
cultivars. The finding reveals that different pomegranate cultivars exhibited
different pattern of antimicrobial activity against S. aureus, P. aeruginosa
and C. albicans. Three of the
pomegranate cultivars exhibited no antifungal activity against C. albicans. Thus, it can be
hypothesized that the pomegranate cultivar used in the current study is
probably one of the cultivars which do not have antifungal activity.
Optimization of Punica granatum gel
gel has inferior activity in treating skin infection caused by S. aureus and P. aeruginosa. Besides, the gel has no antifungal activity against C. albicans. The gel formulation can be
optimized so that it will have significant antimicrobial activity in treating
skin infection. Optimization of the formulation can be done by varying the
carbopol concentration, type of pomegranate cultivar and by using local
way to optimize the gel is by choosing the right carbopol concentration of the
gel as carbopol concentration will affect the release of active constituent.
Previous studies have shown that increasing concentration of carbopol increases
the viscosity of gel (11,17). As the viscosity of gel increases the percentage
of cumulative drug release decrease. Therefore, based on the previous studies
it can be hypothesized that increasing concentration of carbopol reduce
cumulative release of drug. During preliminary study, carbopol concentration
was chosen based on the amount used in a few previous studies. The gel produced
was too viscous which means a lesser amount of carbopol can be used to induce
gelation. So using lesser amount of carbopol may increase the cumulative
release of active ingredient of P.
granatum from gel matrix. Thus, using less amount of carbopol may
potentially increase the antibacterial activity of PG100% gel against S. aureus and P. aeruginosa.
antimicrobial activity of P. granatum
gel may be enhanced by selecting the right cultivar. Different pomegranate
cultivars exhibit varying degree of antimicrobial activity (2). Some of the
cultivars have both antifungal and antibacterial activity and some have only
one function. The efficacy of antimicrobial activity also varies between
cultivars. Therefore, the choice of cultivars is critical. Further research is
required in order to determine the range of cultivars available in Malaysia
that possess superior antimicrobial activity against specific microorganisms.
It is best to choose cultivars with both antifungal and antibacterial activity
so that P. granatum gel can be
use of local fruits can influence the antimicrobial activity of P. granatum gel against skin infection.
As been described earlier, local pomegranate contain higher phenolic compound
that responsible for antimicrobial activity (9,15).
Effect of temperature on characteristic
and antibacterial activity of Punica
granatum gel after a month.
general, increasing the storage temperature causes a decrease in the
antibacterial activity of PG100% gel. A possible reason for the reduced of
antibacterial activity of gel is the
degradation of active constituent responsible for antibacterial activity.
Chemical constituent of P. granatum
responsible for antimicrobial activity is phenolic compound including
pelargonidin-3-galactose, cyanidin-3-glucose, gallic acid, quercetin and
myricetin (15). Pelargonidin-3-galactose and cyanidin-3-glucose are anthocyanin.
A number of studies reported that anthocyanin degrades at high temperature.
Previous study showed that degradation of red currant juice anthocyanin takes
place at temperature above 30°C (12). Similarly, another previous study
revealed that degradation of anthocyanin is 10.7 times faster at 37°C than the
extract and gel formulation of P. granatum peel have been shown to
possess good antibacterial activity against S.
aureus, S. epidermidis and P. aeruginosa. The extract, however, did
not exhibit any antifungal activity against C.
albicans. P. granatum showed promising activity against S. epidermidis followed by S. aureus and finally P. aeruginosa. PG100% gel was chosen as
the best formulation because after a month of storage at different temperature,
it was still homogenous, showed no phase separation, did not change its colour
and had good consistency. More importantly, PG100% gel exhibited the highest
antibacterial activity. Moving forward, P.
granatum has the potential to be formulated as gel to treat bacterial skin
infection caused by S. aureus, S. epidermidis, and P. aeruginosa. However, further studies are required in order to
optimize the antimicrobial activity of P.
deepest appreciation to Cyberjaya University College of Medical Sciences for
funding this research.
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