Phytochemical Screening and Antibacterial Effect of Methanol Extracts of Suaeda aegyptiaca Leaves on Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa

1. Introduction

Medicinal plants are thought to be a rich source of medicinal compounds that have been shown to treat infectious diseases. Traditional remedies are well documented and widely used in developing nations, where medicinal plants have been used as a replacement for antibiotics which have side effects and develop resistance to numerous therapies ( 1 - 5 ). Since the majority of plants include various active chemicals, such as flavonoids, tannins, and alkaloids, they provide a plentiful supply of antimicrobial agents against infectious diseases caused by bacteria, fungi, viruses, insects due to their anti-inflammatory activity and immunomodulatory effect ( 6 - 12 ).

Suaeda aegyptiaca, a member of the Chenopodiaceae family, is found throughout Europe, the Canary Islands, and the Mediterranean region, Australia, Asia, as well as Argentina, and North America. It can be found throughout Arabia in saline settings, particularly along the beaches, and grows in a variety of plant groups and fields ( 13 ). Since this plant appears deeper or blackish when dried, Suaeda takes its name from the Arabic word suwaid ( 14 ). The herb S. aegyptiaca has been used in folk medicine to treat stomachache, wounds, and skin infections ( 15 ). Considering the significance of therapeutic herbs, the present study aimed to assess the antibacterial activity of a methanol extract of Suaeda aegyptiaca leaf in vitro by evaluating its effects on bacterial biological activity inhibition, as well as its screening phytochemical ingredients, in an attempt to find new compounds and alternative treatments for the diseases caused by harmful microorganisms.

2. Materials and Methods

Suaeda aegyptiaca leaves were collected in Thi-Qar from a variety of sources. The plants were powdered and stored in a sterile container until they were needed.

2.1. Preparation of Crude Extracts

A powdered sample of 20 g was extracted in a Soxhlet device with 200 mL of methanol at room temperature. Until the usage, the samples were maintained at 40°C. A 20 mg/mL stock solution was made. Stock solutions were prepared one day ahead of time. For initial testing and retests, several aliquots of each sample were stored ( 16 , 17 ). Stock solutions were sterilized after being filtered. On the day of the assay, an aliquot of frozen stock solution was thawed in the refrigerator. By serial dilution, a concentration of 100 g/ml of extract was obtained. The crude extracts were then diluted to reach concentrations of 2.5%, 5%, and 10%.

2.2. Screening of Phytochemical Constituents

Suaeda aegyptiaca phytochemical components were qualitatively evaluated utilizing various standardized test methodologies ( 18 , 19 ) as displayed in table 1.

2.3. Test Microorganisms and their Sources

S. aureus, S. epidermides, E. coli, and P. aeruginosa isolates were obtained from the Department of Biology at Thi-Qar University College of Science. The API Staph. and API Enterobacteracea ( 21 ) were used to confirm the bacterial species. The bacteria were obtained from clinical specimens. Nutrient agar slants were used to subculture the pure cultures. They were kept at 40°C until they were needed for the investigation.

2.4. Antibacterial Assay

The  Kirby-Bauer test, known as the disk-diffusion method ( 22 ), was used to screen methanolic extracts of Suaeda aegyptiaca leaves for antibacterial activity in vitro.  The sterile petri-plates were filled with sterilized nutritional agar medium (20 ml) and allowed to harden. The bacterial broth cultures were swabbed individually on an agar plates using a sterile bud. The wells (5 mm in diameter) were drilled into the agar with a sterile borer. Plant organic extracts were placed into each well aseptically and incubated at 37°C for 24 h. A measurement of the inhibitory zone was made. Antibacterial activity was measured using the diameter of the inhibition zone (DIZ) of the examined bacterium. The DIZ was measured in millimeters. All experiments were carried out in triplicate using the methods described in a previous study ( 23 ).

2.5. Statistical Analysis

Each experiment was carried out in triplicates, with the means from absolute data being reported. According to Box, Hunter ( 24 ). The data were analyzed in SPSS software using the ANOVA test.

3. Results and Discussion

The phytochemical screening of Suaeda aegyptiaca revealed the presence of alkaloids, tannins, sterols and/or terpenes, flavonoids, and saponins, but no anthraquinones or coumarins, as depicted in table 2.

According to the results of an antimicrobial assay using the agar diffusion method (wells of medium agar are filled with sample extracts), methanol extracts of the S. aegyptiaca plant showed potent antibacterial inhibitory zones against E. coli, P. aeruginosa, S. aureus, and S. epidermidis. Crude methanolic extract of S. aegyptiaca has a significant inhibitory effect on S. epidermidis. Figure 1 illustrated that the inhibitory zones had diameters of 24.7%, 21%, and 12.7% mm at the concentrations of 10%, 5%, and 2.5 %, respectively. Based on figure 2, the sizes of the inhibition zones against S. aureus ranged from 20-13.3 mm at the concentrations of 10%, 5%, and 2.5 %, respectively. The inhibitory impact of the extract was stronger since the concentration of the extract was raised.

Figure 1. The effect of crude methanol extract of S. aegyptiaca against S.epidermidis

Figure 2. The effect of crude methanol extract of S. aegyptiaca against S. aureus

Figure 3 displays the effect of S. aegyptiaca extracts on Escherichia coli. The higher mean zone of inhibition was determined to be 18.7 mm at 10% con. At 5% and 2.5 %, the additional zones of inhibition are 16.7 and 11.3 mm, respectively. As illustrated in figure 4, the mean inhibition zone against P. aeruginosa was 16.3, 13.3, and 9.3 mm at 10%, 5%, and 2.5 % con, respectively.

Figure 3. The effect of crude methanol extract of S. aegyptiaca against E coli

Figure 4. The effect of crude methanol extract of S. aegyptiaca against P. aeruginosa

The extract under investigation was examined for inhibitory effect against tested microorganisms that cause human diseases since the efficiency of the extract varied depending on the type of bacteria. As demonstrated in figure 5, Staph. epidermids had the highest inhibition zone of 19.4 mm, when compared to other bacteria with inhibition areas of 17.1, 15.6, and 13, respectively, for Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa.

Figure 5. Effect of crude methanol extract of S. aegyptiaca against types of bacteria species

Figure 6 presents that ethanolic extracts of S. aegyptiaca have antibacterial efficacy against both Gram-positive and Gram-negative human pathogenic bacteria. The antibacterial efficiency of ethanolic extracts of Suaeda aegyptiaca against both Gram-positive and Gram-negative human pathogenic bacteria is displayed in figure 6 and 7. Positive bacteria were more effective, with a mean inhibition of 18.28 mm, as compared to negative bacteria which was inhibited by 14.28 mm.

Figure 6. Effect of crude methanol extract of S. aegyptiaca against types of Grams,stain bacteria

Figure 7. Inhibition zone created by S. aegyptiaca

The results of the present research revealed that the current extracts were more efficient against Gram positive bacteria. This finding is consistent with those obtained in earlier studies ( 25 - 27 ) which indicated that the presence of outer membrane lipopolysaccharides is responsible for higher resistance of Gram-negative bacteria to plant extracts. Many investigations have found that herbal antimicrobial compounds are unable to stop the growth of Gram-negative bacteria due to the presence of a sophisticated cell wall construction that prevents herbal extracts from penetrating bacterial cells. Nevertheless, in the current investigation, the extracts inhibited the growth of numerous bacteria, demonstrating their potential to penetrate bacterial cells ( 28 , 29 ).  Pseudomonas aeruginosa (P. aeruginosa) as a Gram-negative bacterium has a high level of natural resistance to nearly all known antimicrobials, antibiotics, and even manufactured medicines owing to its outer membrane barrier.

In the current results, nonetheless, the extracts prevented the growth of this bacterium, revealing its ability to permeate bacterial cells ( 30 ). Plant-derived flavonoids, terpenoids, and steroids have sparked a lot of attention in recent years due to their wide range of pharmacological effects, such as antibacterial, antioxidant, and anticancer activities. Consistent with previous studies, the effectiveness of this extract is due to its active chemical compounds, pointing to the presence of alkaloids, stimulants, coumarins, catechins, tannins, phenols, flavonoids, saponins, glycosides, and the bioactive xanthoprotein of the leaves of Suaeda monoica, which were used as a treatment for hepatitis and as an ointment for wounds and antiviral ( 31 , 32 ).

As evidenced by the results of the present study, this extract inhibited both Gram positive and negative bacteria, indicating that they have a broad spectrum inhibitory effect. Gram positive bacteria were more susceptible to the extracts than the Gram-negative bacteria, indicating that it could be utilized to treat infections caused by resistant germs.

Authors' Contribution

Study concept and design: S. R. N.

Acquisition of data: D. H. M.

Analysis and interpretation of data: Z. K. H.

Drafting of the manuscript: S. R. N.

Critical revision of the manuscript for important intellectual content: D. H. M.

Statistical analysis: Z. K. H.

Administrative, technical, and material support: S. R. N.

Conflict of Interest

The authors declare that they have no conflict of interest.

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