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Daun Sayson

on 10 September 2014

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Submitted by:
Bayawa Holyfield M.
Sayson Daun Pocholo G.
Submitted to:
Sir. Daryl Magalgalit

To determine the antibacterial potential of guava (Psidium guajava) leaf extracts against Escherichia coli which is foodborne and spoilage bacteria. The guava leaves were extracted in one solvent (ethanol, and water). The efficacy of these extracts was tested against those bacteria through a well-diffusion method employing 50 μL leaf-extract solution per well. According to the findings of the antibacterial assay, the ethanol extracts of the guava leaves showed inhibitory activity against e. coli bacteria, whereas the e. coli bacteria were resistant to the solvent extract. On the basis of the present finding, guava leaf-extract might be a good candidate in the search for a natural antibacterial agent. This study provides scientific understanding to further determine the antibacterial values and investigate other pharmacological properties.
Recently there has been a lot of attention focused on producing medicines and products that are natural. Several fruits and fruit extracts, as well as arrowroot tea extract and caffeine, have been found to exhibit antibacterial activity against E. coli . This suggests that plants which manifest relatively high levels of antibacterial action may be sources of compounds that can be used to inhibit the growth of foodborne pathogens. Bacterial cells could be killed by the rupture of cell walls and membranes and by the irregular disruption of the intracellular matrix when treated with plant extracts.
The guava (Psidium guajava) is a phytotherapic plant used in folk medicine that is believed to have active components that help to treat and manage various diseases. The many parts of the plant have been used in traditional medicine to manage conditions like malaria, gastroenteritis, vomiting, diarrhea, dysentery, wounds, ulcers, toothache, coughs, sore throat, inflamed gums, and a number of other conditions. This plant has also been used for the controlling of life-changing conditions such as diabetes, hypertension, and obesity. In this study, we aim to evaluate the total extracts of P. guajava leaves, using various aqueous and organic solvents to establish if it is effective against killing or inhibiting the growth of foodborne bacterium Escherichia coli, which can cause foodborne illness and spoilage.
What is phytotherapic???
use of extracts of natural origin as medicines or health-promoting agents.
2.1. Preparation of Plant Extract
The leaf samples were collected from the guava trees growing at Guisad Valley, Baguio City. Random leaf samples were collected into plastic bags.
2.2. Extraction Methods Used on Guava
The leaf samples were washed in tap water, dried, and placed into a blender to be grounded into powder.
The mixtures were made in sterile 125 mL Erlenmeyer flask wrapped in aluminum foil to avoid evaporation and exposure to light for 3 days at room temperature. After 3 days of soaking in solvent, the mixtures were transferred to 50 mL tubes and centrifuged for 10. The supernatant was collected.
2.3. Phytochemical Analysis
Chemical tests for the screening and identification of bioactive chemical constituents in the guava were carried out with the extracts using the standard procedure as described. For each test, 1 mL of each solvent extract was used for analysis, in exception for the saponin test in which 3 mL solvent extract was used.
2.4. Test for Saponins
Extract was placed in a test tube and shaken vigorously. The formation of stable foam was taken as an indication for the presence of saponins.
2.5. Test for Phenols and Tannins
Extract was mixed with 2 mL of 2% solution of FeCl3. A blue-green or black coloration indicated the presence of phenols and tannins.
2.6. Test for Terpenoids (Salkowski’s Test)
Extract was mixed with 2 mL of chloroform. Then 2 mL of concentrated sulfuric acid was added carefully and shaken gently. A reddish brown coloration of the interphase was formed to show positive results for the presence of terpenoids (Figure 2(c)).
2.7. Test for Flavonoids (Shinoda Test)
Extract was mixed with magnesium ribbon fragments, and concentrated hydrochloric acid was added drop wise. Orange, red, pink, or purple coloration indicates the presence of flavonoids.
2.8. Test for Glycoside
Extract was mixed with 2 mL of glacial acetic acid containing 2 drops of 2% FeCl3 . The mixture was poured into another tube containing 2 mL of concentrated sulfuric acid. A brown ring at the interphase indicates the presence of glycosides

3. Results and Discussions

The analysis of the plant extracts revealed the presence of phytochemicals which are known to exhibit medical and physiological activities. For example, tannins are polyphenolic compounds that bind to proline rich protein that interferes with protein synthesis and has shown to have antibacterial activity.
Flavonoids are hydroxylated polyphenolic compounds known to be produced by plants in response to microbial infections to which this aspect has been extensively studied and found to have antimicrobial activity against an array of microorganisms in vitro.
Their ability has been attributed to their ability to form complexes with extracellular and soluble proteins and bacterial cell walls. Terpenoids although mainly used for their aromatic qualities have also been found to be potential agents against inhibiting bacteria. Saponins which are glycosides have been found to have inhibitory effects on gram-positive organism, S. aureus. Therefore, the phytochemical analysis revealed that the methanol, ethanol, and distilled water extract have chemical compounds that have been found to possess antibacterial activities, which could contribute to the results obtained from antibacterial analysis.

Antibacterial Activity
The results of the study indicated that only two of the crude solvent extracts prepared from the leaves ofPsidium guajava, methanol and ethanol, showed inhibitory activity against bacteria. Only Gram-positive bacteria, Bacillus cereus and Staphylococcus aureus, were susceptible to the two extracts, while neither of the Gram-negative bacterium showed any inhibition. At 10 mg/50 µL, the methanol extract had a slightly higher antibacterial activity with mean zones of inhibition 8.27 and 12.3 mm than ethanol extract with mean zone of inhibition 6.11 and 11.0 mm against B. cereus and S. aureus, respectively. The resistance of the Gram-negative bacteria could be attributed to its cell wall structure. Gram-negative bacteria have an effective permeability barrier, comprised of a thin lipopolysaccharide exterior membrane, which could restrict the penetration of the extruding the plant extract. It has been reported earlier that Gram-negative bacteria are usually more resistant to the plant-origin antimicrobials and even show no effect,

compared to Gram-positive bacteria. Gram positive bacteria have a mesh-like peptidoglycan layer which is more accessible to permeation by the extracts

Table 1 shows the summarized phytochemical screening of chemical constituents of guava extracts under study on qualitative basis. The results revealed the presence of active compounds in the four different extracts. As the table shows, the methanol and ethanol extracts indicate the presence of tannins, phenols, flavonoids, terpenoids, and glycosides, but absence of saponins. Distilled water is the only that showed the presence of all the phytochemicals, whereas solvent n-hexane failed to have any of the chemical compounds present.

+: presence of constituent (positive); −: absence of constituent (negative).
Table 1: Phytochemical constituents of Psidium guajava extracts.
4. CONclusions
The present work demonstrates the antibacterial potential of Psidium guajava leaves extract by using various solvents. The results indicate that ethanol is better than n-hexane and water for the extraction of the antibacterial properties of guava. The results also indicate that the plant extracts have no antibacterial effect on the Gram-negative bacteria, showing that they do not contain active ingredients against the organisms. Comparisons with related data from the literature indicate that according to the different methodologies of studies on antibacterial activity, the most diverse outcomes can be obtained. This study provides scientific insight to further determine the antimicrobial principles and investigate other pharmacological properties of guava.
The researchers would like to thank Almighty God and . And of course their Research II teacher Mr. Daryl Magalgalit, their parents and the others who supported the researchers and this study in any method wether moral/financial.
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