Antibacterial Properties of Cajanus cajan leaf plant against S.mutansElvin Morales¹, Nicole Colón¹, Carmary Soto¹

¹Universidad de Puerto Rico, Cayey

Abstract: Cajanus Cajan has proved to be an excellent source of anti-bacterial materials. Previous studies have shown that Cajanus Cajan leaf extract can serve as a potential anti-bacterial agent against gram-positive bacteria. This study aims prove if Cajanus cajan contain anti-bacterial properties against S.mutans. Nine Petri dishes, divided into three groups, were prepared during this experiment. S.mutans was added to the nine Petri dishes using bacterial lawn technique. A sterile filter paper disc was added to each of the petri dishes: three containing the filtered extract, three containing the unfiltered extract and the remaining three without extract.

Introduction: Cajanus Cajan, also called

Pigeon Pea plant, is a short-term perennial shrub that reaches 4-5 m in height and belongs to the Fabaceae family of the Dicot group. The pigeon pea plant is also rich in proteins, carbohydrates and minerals and it occurs mostly in South and Central America, the Caribbean, and Africa. Some of its medicinal applications include the treatment of anemia hepatitis, diabetes, urinary infections, and yellow fever, with the leaves used to treat coughs, fevers, ulcers, and skin irritations.

Streptococcus mutans is a non-motile bacterium that inhabits the human oral cavity. It produces plaque and acids that break down tooth enamel and cause dental cavities, a hole or holes in the outer two layers of a tooth, the enamel and the dentin, and “it makes up thirty to sixty percent of the total bacteria inhabiting the surfaces of human teeth, tongue, cheeks, and in saliva (John, Lewis 2002)”. This disease represents a major problem in the U.S. today, and over two billion dollars are spent each year for treatment. S. mutans is also a heterotrophic organism, which means that it cannot synthesize reduced

organic compounds from inorganic sources and that it must obtain them by eating other organisms. It utilizes sucrose to produce a sticky polysaccharide that permits them to cohere to one another forming plaque, and to produce lactic acid [1]. The combination of plaque and lactic acid leads to the breakdown of tooth enamel, which results in dental decay or cavities. It posses special channels in their cell walls and membranes which allows or aids molecules to cross, which is how they get their food. S.mutants reproduces asexually, primarily by binary fission, which is a type of cell division yielding two identical bacteria. Streptococcus mutans is a facultative anaerobe, and its ideal living conditions require a 70% CO2 atmospheric concentration.

Previous studies have indicated that the leaf is an excellent source of anti-bacterial materials but also that a component inside the Cajanus cajan leaf extract, called Cajanuslactone, is “a potential anti-bacterial agent against Gram-positive bacteria” (Kong et al. 2010). A similar experiment (Morales and Morales 2006) was done where a Cajanus cajan mouthwash was developed from the leaf extract and

was tested to see if it would inhibit the growth of Streptococcus mutans [4]. The mouthwash did indeed inhibit bacterial growth. This experiment will

test the anti-bacterial potential of the leaf extract against Streptococcus mutans.

Materials and Methods

During this experiment 3g of Cajanus Cajan were grinded using a mortar and a pestle. Silica Gel Desiccant was added during the grinding of the leaves to help the efficiency during the process. To finish grinding the leaves a blender was used adding to it 30 mL of water. The resulting extract was filtrated using a vacuum pump. After that, Streptococcus mutans was added to nine Petri dishes with nutrient agar by making a lawn using sterile swabs following the aseptic techniques. One sterile filter paper disc was added to each Petri dish: three with filtrate extract, three with unfiltered extract, and the other three remaining, without extract, being these ones the control for the experiment. The nine Petri dishes were incubated at 37C in a BBL GasPack, which create an anaerobic environment for 5 days.

Results:According to the observations

made after the period of bacterial incubation (5 days), only the filtered leaf extract showed signs of inhibiting bacterial growth of the Streptococcus mutans, as shown in image 2. However there was a slight discrepancy in the results (the 4.3mm inhibition zone in Trial 3 of the filtered leaf extract). The unfiltered leaf extract, shown in image 1, didn’t inhibit the growth of the bacteria at all. The control (Image 3) showed the expected result of unhampered bacterial growth, in Trial 2, however, there was a slight inhibition zone of 0.9mm. Figure one

showed all the inhibition zones measurement of the Petri dishes in millimeters.

Image 1:

Image 2: (Highlighted Inhibition Zones)

Image 3:

Table 1: Inhibition zone measurements

Measurements in mmTrial 1 Trial 2 Trial 3

Cajanus cajan leaf

extract (not

filtrated)

0.0 0.0 0.0

Cajanus cajan leaf

extract (filtrated)

1.3 1.8 4.3

Control 0.0 0.9 0.0

Figure 1: Inhibition zone measurements – showed the different inhibition zone of the three replicates in millimeters. Controls contain only bacteria without any kind of extract.

Discussion:In conclusion, this study proved

that Cajanus Cajan leaf extract does in fact contain anti-bacterial properties and it is able to inhibit the growth of S.mutans. As shown in the results, only the filtrated leaf extract inhibited the growth of S.mutans. The discrepancy that occurs in Trial 3 of the filtrated leaf extract was due to the fact that in the process of placing the filter paper it fell in a corner of the agar plate and was then moved to the center, thus amplifying the inhibition zone, as

show in figure 1. The unfiltered extract showed no inhibition of S.mutans this may be due to the presence of leaf particles that contained substances and other contaminations that decreased the antibacterial potential of the extract. Trail 2 of the Control showed a 0.9mm making this data suspicious, because the control samples didn’t contain any leaf extract or any anti-bacterial agent. It was inferred that this happened because an error occurred during the bacterial lawn technique of S.mutans, and a small area next to where the filter paper was placed contained no bacteria at all. Comparisons with the other experiments that were researched further prove the validity of the results that were obtained. Finally, these series of experiments may give rise to the possibility of applying this leaf extract into plaque and cavity treatments.

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