Potential Antibacterial and Antioxidant Activiy of Methanolic
Extract of Vigna unguiculata (L.) Walp Leaves
Sovia Lenny*, Dinda Widya Rizky
Departemen of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Sumatera Utara
Keywords: Antibacterial, Antioxidant, Methanol extract, Vigna unguiculata (L.) Walp.
Abstract: This study was performed to determine the bioactivity of methanolic extract of Vigna unguiculata (L.) Walp
leaves as potential antibacterial and antioxidant. Based on the phytochemical screening, the methanolic
extract of methanolic extract of V. unguiculata (L.) Walp leaves showed the presence of phenolic, terpenoid
and saponin. The 15 wt.% of methanolic extract of V. unguiculata (L.) Walp leaves exhibited a moderate
antibacterial activity against Gram positive bacterium (S. aureus) with 15.5 cm of inhibition zone diameter.
But negative result was obtained against Gram negative (E. coli). The antioxidant activity of methanolic
extract of V. unguiculata (L.) Walp leaves against DPPH that determined as IC50 was 66.71 mg/L.
1 INTRODUCTION
Vigna unguiculata (L.) Walp is the original plant
from Africa to cure epilepsy, chest pain, and
constipation (Kritzinger, 2005). Vigna unguiculata
(L.) Walp also can be used as the source of protein
and other nutritions (Siddhuraju, 2007).
Insect pest is still an issue for the Vigna
unguiculata (L.) plantation in Africa. There is a
correlation between the concentration of flavonoid/
antochyanine that presence in V.unguiculata (L.) and
the ability to inhibit the attack of insect pest (Makoi,
2010).
The HPLC meaurement of V.unguiculata showed
the presence of three aglycon flavonoid, i.e.
quercetin, kaempferol, and isorhamnetin. Also, the
resistency correlation between insect pest and
flavonoid content. This result showed that the
presence of quercetin and isorhamnetin play a role in
the resistency mechanism (Latannzio, 2000).
Other than flavonoid compound, phenolic and
tannin can be found in the seed of V.unguiculata and
the processed V.unguiculata is claimed as the strong
antioxidant sources. This is as the impact of the
formation of complex between tannin and protein,
and the presence of phenolic compound in the
dietary based on V.unguiculata. The presence of the
potential antioxidant compound in the V.unguiculata
can protect the human body from oxidative process
(Siddhuraju, 2007).
The objective of the current research was to
determine the antibacterial and antioxidant activity
of V.unguiculata (L.) Walp leaves.
2 EXPERIMENTAL
2.1 Materials
Equipment : glassware, rotary evaporator, petri
dish, spectrophotometry UV-Vis.
Materials : leaves of V. unguiculata (L.) Walp., 5
wt.% of FeCl
3
, ethyl acetate,
Lieberman-Burchard’s reagent, NA
medium, MHA medium, DMSO,
distillate water, DPPH, methanol,
culture of S. aureus and E. coli.
2.2 Extraction of V. unguiculata (L.)
Walp Leaves
About 600 g of simplicia of V. unguiculata (L.)
Walp leaves was macerated in 4 L of methanol. The
filtrate was separated and concentrated using rotary
evaporator. The obtained extract was named as
concentrated methanolic extract.
Lenny, S. and Rizky, D.
Potential Antibacterial and Antioxidant Activiy of Methanolic Extract of Vigna unguiculata (L.) Walp Leaves.
DOI: 10.5220/0008878602150217
In Proceedings of the 1st International Conference on Chemical Science and Technology Innovation (ICOCSTI 2019), pages 215-217
ISBN: 978-989-758-415-2
Copyright
c
2020 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved
215
2.3 Antibacterial Activity of
V. unguiculata (L.) Walp Leaves
The concentration of methanolic extract of V.
unguiculata (L.) Walp leaves was varied to be 5, 15
and 25 wt.% in DMSO. Mueller Hinton Agar
(MHA) medium was poured into petri dish in the
temperature of 45-50
o
C and the bacterium
suspension was spread in the medium. The
antibacterial was determined using dish paper
method. The incubation of treated medium was kept
at 35
o
C for 18-24 h. S. aureus and E. coli were
chosen as tested bacterial.
2.4 Antioxidant Activity of
V. unguiculata (L.) Walp Leaves
The antioxidant activity of methanolic extract of V.
unguiculata (L.) Walp leaves was determined using
spectrophotometer UV-Vis as an impact of colour
changed due to the reaction between of DPPH and
the extract. w milligram of DPPH was dissolved in
methanol until its volume 450 mL with the final
concentration of DPPH was 50 µM. The
concentration was varied to be 5, 10, 15 dan 20 ppm.
One millilitre of DPPH 50 µM was mixed with
2 mL of methanolic extract of methanolic extract of
V. unguiculata (L.) Walp leaves. The mixture was
homogenized, and it was left dark condition for 30
minutes. The absorbance of extract was measured at
516 nm. The inhibition percentage was determined
from the equation below:
%
100% (1)
3 RESULT AND DISCUSSION
3.1 Antibacterial Activity
The antibacterial properties of methanolic extract of
V. unguiculata (L.) Walp leaves was evaluated
against S. aureus and E. coli. The diameter of
inhibition zone was appeared as a clear zone around
the paper dish that used in antibacterial evaluation.
The inhibition zone result was showed in Table 1.
Table 1: The antibacterial activity of methanolic extract
of V. unguiculata (L.) Walp leaves
No Concentration (%)
Diameter of
inhibition zone (mm)
S. aureus E. coli
1 5 14 -
2 15 15,5 -
3 25 15 -
Based on that result, the methanolic extract of
methanolic extract of V. unguiculata (L.) Walp
leaves has a moderate potency to inhibit S. aureus
but diameter of inhibition was not found in E. coli.
The moderate potency of the extract had an
inhibition zone diameter was 15.5 mm.
The different result between the both bacterial
can be caused there was no active compound that
can be found presence of active compound that can
inhibit E. coli. Also, this assumption can be caused
by the different of cell walls structure in the Gram
and Positive negative. Bacterium Gram positive has
single laye with low lipid content (1-4%) and the
Gram negative bacterium has higher lipid content
(11-12%) and the outer membrane has three
component that constructed by liposaccharide,
lipoprotein, and phospholipid (Fardiaz, 1992).
3.2 Antioxidant Activity
The antioxidant activity determination of methanolic
extract of V. unguiculata (L.) Walp leaves was
carried out using DPPH method and the absorbance
was measured using spectrophotometer UV-VIS at
516 nm of wavelength. The following result in Table
2 was the absorbance of methanolic extract at
various concentration.
Table 2: Absorbance of methanolic extract of V.
unguiculata (L.) Walp leaves
No Concentration (ppm) Absorbance
1 Blank 0,963
2 5 0,864
3 10 0,843
4 15 0,832
5 20 0,810
The radical scavenging activity of this
methanolic extract were determined as %inhibition.
Minami et al (1998) The %inhibition of antioxidant
was categorized according to IC50 value. The
antioxidant molecules were categorized as very
strong antioxidant activity when the IC50 ≤ 10,
strong antioxidant activity when the IC50 between
10 and 100, and the poor antioxidant activity when
ICOCSTI 2019 - International Conference on Chemical Science and Technology Innovation
216
the IC50 > 100. The IC50 of methanolic extract of
V. unguiculata (L.) Walp leaves was obtained using
regression linear equation with value of 66.71 mg/L.
Based on the Minami classification, this methanolic
extract has strong antioxidant activity.
4 CONCLUSIONS
The evaluation of the 15 wt.% of methanolic extract
of V. unguiculata (L.) Walp leaves as potential
antibacterial showed a moderate diameter inhibition
zone against S. aureus with value 15.5 mm. The
antioxidant activity of the methanolic extract has
strong antioxidant activity with IC50 of 66.71 mg/L.
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Potential Antibacterial and Antioxidant Activiy of Methanolic Extract of Vigna unguiculata (L.) Walp Leaves
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