5 DISCUSSION
Based on Tables 1 and 2, concentration of 20% is the
highest concentration with moderate inhibition for the
growth of S. aureus and E. coli; as a reference from
Table 3, the diameter of the inhibition zone 5-10 is in
the moderate category.
Avocado leaves are plants that are widely used for
treatment because they have an antibacterial effect.
Avocado leaf extract is able to inhibit the growth of
S. aureus and E. coli. The leaves consist of active
compounds resulting in antibacterial properties such
as flavonoids, saponins, alkaloids, tannins, and
polyphenols.
Flavonoids have antibacterial effects by inhibiting
bacterial DNA function. In this process, some errors
might be found in bacterial replication and
translation. Inhibition occurs when the bacterial
cytoplasmic membrane which consists of lipids and
amino acids removes the alcohol group in the
flavonoid compound. This process will damage the
cell walls, and thus the compound can enter the
nucleus of the bacterial cells (Pisoschi & Pop, 2015).
Saponin compounds in avocado seeds can also
have antibacterial properties which have the same
mechanism of action as flavonoid compounds.
Tannins are active compounds in avocado seeds. The
way tannin produces an antibacterial effect is by
precipitating bacteria and their proteins. The effect of
the antibacterial content in tannin will disrupt the
function of genetic materials and inactivate enzymes,
causing bacterial cells not to form (Dwi, Tanjung,
Chairani, Bikarindrasari, & Dewi, 2021).
The mechanism of alkaloids in inhibiting bacterial
growth works by damaging the constituent
components of peptidoglycan in bacterial cells; as a
result, the cell wall layer is not formed completely
and causes cell deaths. In addition, alkaloids have an
inhibitory mechanism by binding to DNA
presumably because the alkaloids have a base group
that contains nitrogen. This base group will react to
acidic compounds in bacteria such as DNA which is
the main constituent of the cell nucleus. With the
disruption of DNA, the synthesis of proteins and
nucleic acids in cells will be disrupted. As a result,
cell metabolism is distracted, and bacterial growth is
inhibited or stopped (Isnarianti, Wahyudi, & Puspita,
2013).
6 CONCLUSIONS
Avocado leaf extract is effective in inhibiting the
growth of S. aureus and E. coli with an average
diameter of the inhibition zone that varies depending
on the concentration of each extract. The content of
metabolite compounds found in avocado leaves has
the potential to inhibit the growth of these bacteria.
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