Abstract
Antimicrobial resistance poses a global public health threat, compelling the search for alternative treatments, especially in resource-limited settings. The increasing ineffectiveness of traditional antibiotics has intensified the need to explore medicinal plants as viable therapeutic options. This study sought to compare the efficacy of certain medicinal plants used in Owerri, Nigeria, for treating pathogenic bacteria against traditional commercial antibiotics. We tested graded concentrations (25 mg/ml, 50 mg/ml, 75 mg/ml, and 100 mg/ml) of ethanolic extracts of Awolowo leaf (Chromolaena odorata), Bitter leaf (Vernonia amygdalina), and Lemon grass leaf (Cymbopogon citratus) against Salmonella spp, Klebsiella spp, Escherichia coli, and Staphylococcus aureus employing the agar well diffusion method to measure zones of inhibition. Commercial antibiotics studied included: Pefloxacin, Gentamycin, Ampiclox, Zinnacef, Amoxicillin, Rocephin, Ciprofloxacin, Streptomycin, Septrin and Erythromycin, Sparfloxacin Amoxicillin, Augmentin, and Tarivid. Each experiment was conducted in triplicate to ensure accuracy and reproducibility. Results were analyzed descriptively and presented as mean zones of inhibition and standard deviations. One to three plant species exhibited antibacterial activities (zones of inhibition) across 25–100 mg/ml concentrations. In contrast, some or all antibiotics only exhibited antibacterial activities at 100 mg/ml concentration (none at 25–75 mg/ml concentrations). Zones of inhibition (10.3–14.1 mm) of all three plant species against E.coli and Klebsiella at 100 mg/ml concentration were higher than those of 8–10 antibiotics. C. odorata had shown high zones of inhibition of 11.8 and 11.0 mm against Salmonella spp. and S. aureus at 100 mg/ml concentration, which were higher than those of eight antibiotics. The other two plant species (C. citratus and V. amygdalina) had exhibited low zones of inhibition against Salmonella spp. and S. aureus, which were higher than those of 3 or 4 antibiotics at 100 mg/ml concentration. In general, the antibacterial activities of the three plant species across 25–100 mg/ml concentrations were higher than those of many antibiotics. To a large extent, the efficacy of medicinal plant extracts across different concentrations against bacterial strains was higher than that of many antibiotics. Those plant species have therefore shown some potential to be used as alternative or complementary therapeutics to antibiotics in addressing antibiotic resistance. Since the promising findings were based on an in vitro study, we recommend clinical trials to establish safe and effective doses of those plant extracts in humans.
Keywords: Antibiotics, Crude extracts, Zones of inhibition, Pathogenic isolate
Subject terms: Drug discovery, Microbiology
Background
The widespread misuse and overuse of antibiotics have significantly accelerated bacterial resistance, diminishing the effectiveness of many routine treatments and posing a serious global health threat1,2. This rise in antimicrobial resistance (AMR) necessitates alternative approaches, including developing novel therapies and stewardship strategies to curb the spread of resistant pathogens3.
According to the World Health Organization (WHO), AMR occurs when microorganisms such as bacteria, viruses, fungi, and parasites mutate to withstand conventional treatments. This adaptation makes infections harder to treat and heightens the risk of disease spread, severe illness, and death4,5. AMR has, therefore, become a pressing issue in global health and development, necessitating urgent, multi-sectoral actions to meet Sustainable Development Goals (SDGs)4.
Natural products, particularly medicinal plants, have historically played a critical role in drug discovery and development6. Many plants produce bioactive compounds, such as secondary metabolites, to protect against microbial threats, including bacteria and fungi7. These plant-derived compounds present promising new avenues for treating infections, as they can possess unique antimicrobial mechanisms that may be effective against resistant strains8,9.
In the context of AMR, the medicinal plants Chromolaena odorata (Awolowo leaf), Vernonia amygdalina (Bitter leaf), and Cymbopogon citratus (Lemon grass) are frequently used by local populations in Owerri, Nigeria, to combat infections from pathogenic bacteria. Given their traditional use and the documented antimicrobial properties of these plants, this study aims to evaluate their therapeutic potential against selected bacterial pathogens, comparing the efficacy of their ethanolic extracts with standard clinical antibiotics. This research seeks to determine if these plants offer viable alternative or complementary treatments to conventional antibiotics, particularly in resource-limited settings where AMR poses a significant challenge.
Materials and methods
Collection of plant materials
Chromolaena odorata, Vernonia amygdalina, and Cymbopogon citratus leaves were collected from Umuchima Owerri and FUTO markets situated at an altitude of 150 m. For identification, plant specimens were deposited at the Federal University of Technology Owerri Herbarium as FUTO H 0095, FUTO H 0096, and FUTO H 0097, respectively. Voucher specimens were C. odorata (FHI 105769), V. amygdalina (FHI113105), and C. citratus (FHI 01066410). Identities of those plants were also confirmed by a Botanist from the Department of Biological Science, Federal University of Technology Owerri, Nigeria.
Preparation of plant extraction
Plant leaves were ground with an electric grinder into powdered forms, and 50 g of each of these powdered leaves was suspended in 500 ml of ethanol and allowed to stand for three (3) days. They were filtered using Whatman No. 1 filter paper, and the residues were sundried. The residue and filtrates were kept separately in amber glass bottles to ensure stability and prevent contamination.
Microbial cultures (test organism)
Plant extracts were assayed for antimicrobial activity against four species of bacteria that were used as test microorganisms. The bacterial strains were Gram-positive (Staphylococcus aureus) and Gram-negative: E. coli, Klebsiella spp, and Salmonella spp). All microorganisms were clinical isolates obtained from the Microbiology Laboratory at Federal Medical Centre Owerri, Imo State, Nigeria, and very carefully identified using standard microbiological and biochemical methods (Table 2).
Table 2.
Biochemical tests for the identification of the isolated organisms.
| Biochemical test | E.coli | Klebsiella spp | S. aureus | Salmonella spp |
|---|---|---|---|---|
| Coagulase test | - | - | + | - |
| Catalase test | + | + | + | + |
| Citrate test | - | + | + | + |
| Indole test | + | - | - | - |
| Methyl Red test | + | - | + | + |
| Urease test | - | + | + | - |
| Oxidase test | - | - | - | - |
| Motility test | + | - | - | - |
Key: + = Positive: - = Negative.
Antibiotic susceptibility test
Kirby-Bauer diffusion susceptibility test was employed. Antimicrobial discs specific for either Gram-positive or Gram-negative bacteria were used. The isolates were inoculated onto nutrient media. After the inoculation, diffusion disks with graded concentrations of antibiotics were aseptically impregnated with sterile forceps. The Petri dishes were incubated for 24 h at 37oc in inverted form. This antimicrobial drug sensitivity test was performed according to the guidelines of the Clinical and Laboratory Standards Institute10. After the incubation, the diameters of zones of inhibitions were accurately measured using a transparent short ruler. The antibiotics impregnated on the diffusion disk for Gram-positive bacteria included: PEF-Pefloxacine (10 µg/disk), CN-Gentamycin (10 µg/disk), Ampiclox (30 µg/disk), Zinnacef (20 µg/disk), Amoxicillin(30 µg/disk), Rocephin (25 µg/disk), CPX-Ciprofloxacin (5 µg/disk), S-Streptomycin (30 µg/disk), SXT-Septrin (30 µg/disk) and Erythromycin (10 µg/disk) while the antibiotics impregnated on the disk used for Gram-negative bacteria included: SXT-Septrin (30 µg/disk), CN-Gentamycin (10 µg/disk), CPX-Ciprofloxacin (5 µg/disk), S-Streptomycin (30 µg/disk), CH-Chloramphenicol (30 µg/disk), SP-Sparfloxacin (10 µg/disk), AM- Amoxicillin (30 µg/disk), AU-Augmentin (10 µg/disk), PEF-Pefloxacin (30 µg/disk), Tarivid (10 µg/disk).
Antibiotic susceptibility test using Agar well diffusion method
Graded concentrations of the three plant extracts were prepared (25 mg/ml, 50 mg/ml, 75 mg/ml, and 100 mg/ml). With the aid of sterile glass rods, 5 holes were made on each plate of the test organisms, and with the aid of micropipettes, 1 ml of each concentrated extract was aseptically added to each hole and properly covered. The Petri dishes were properly covered and incubated for 24 h at 37oc. After the incubation, the diameters of zones of inhibitions (Table 3) were accurately measured using a transparent short ruler. This procedural test was performed according to the guidelines of11.
Table 3.
Effect of various concentrations of crude plant extracts on test organisms.
| Zones of Inhibition by Concentration (mg/ml) | |||||
|---|---|---|---|---|---|
| Organism | Extract | 25 | 50 | 75 | 100 |
| E. coli | A | - | 4.24 ± 0.71 | 11.53 ± 0.45 | 12.35 ± 0.31 |
| B | - | - | 3.76 ± 0.26 | 14.10 ± 0.25 | |
| C | 3.56 ± 0.24 | 4.5 ± 0.56 | 2.14 ± 0.64 | 10.30 ± 0.62 | |
| Klebsiella spp | A | - | - | 3.25 ± 0.32 | 15.25 ± 0.25 |
| B | - | 4.65 ± 0.31 | 15.25 ± 0.34 | 16.4 ± 0.84 | |
| C | - | - | 2.67 ± 0.45 | 17.65 ± 0.84 | |
| S. aureus | A | - | - | 3.78 ± 0.9 | 4.23 ± 0.84 |
| B | - | - | - | 6.54 ± 0.52 | |
| C | - | 4.65 ± 0.35 | 3.00 ± 0.8 | 11.03 ± 0.86 | |
| Salmonella | A | - | - | - | 5.20 ± 0.84 |
| B | - | - | - | 5.4 ± 0.8 | |
| C | - | 4.21 ± 0.35 | 2.64 ± 0.3 | 11.82 ± 0.32 | |
Values are in mm and represent mean ± STD (n = 3) A = Cymbopogon citratus, B = Vernonia amygdalina, C = Chromolaena odorata.
Data analysis
Each experiment was conducted in triplicate to ensure accuracy and reproducibility, and the findings were presented descriptively.
Results
The microbial morphology used to accurately and consistently describe the isolated organisms included: size, shape, colour, texture, height, elevation, and odour. Table 1 details the morphological characteristics and Gram-staining results of the microbial isolates used in this study. Escherichia coli, Klebsiella spp., and Salmonella spp. all presented as Gram-negative, non-spore-forming rods with slight variations in colony appearance. E.coli and Salmonella spp. exhibited smooth, convex colonies, with E. coli colonies appearing pink and opaque, while Salmonella spp. showed a greyish-white, translucent morphology. Klebsiella spp. displayed a distinct mucoid texture, indicative of its capsulated form, with pink-red, opaque colonies. Staphylococcus aureus, the only Gram-positive organism among the isolates, was observed as round, smooth, and opaque colonies that were easily emulsified, consistent with typical cocci morphology.
Table 1.
Morphological characterization of Microbial isolates.
| Organism | Gram stain | Colony Morphology |
|---|---|---|
| Escherichia coli | G-ve | Rod, non-spore-forming, convex, smooth, |
| Pink and opaque | ||
| Klebsiella spp. | G-ve | Rod, non-spore-forming, convex, mucoid, |
| Pink-red and Opaque | ||
| S. aureus | G + ve | Round shape (cocci), non-spore-forming, |
| Smooth, pink, Opaque, and easily emulsified. | ||
| Salmonella spp. | G-ve | Rod, non-spore-forming, convex, smooth, greyish white, translucent |
Key: G+ve = Gram positive: G−ve = Gram negative.
Biochemical tests for the identification of test organisms
The biochemical tests (Table 2) provide a means of differentiating between various bacterial species. E. coli is coagulase-negative, catalase-positive, indole-positive, and motile, indicating it performs mixed-acid fermentation. It cannot utilize citrate or hydrolyze urea. Klebsiella spp. is coagulase-negative, catalase-positive, citrate-positive, urease-positive, and non-motile, distinguishing it from E. coli. It does not produce indole and fails the methyl red test. S. aureus is coagulase-positive, catalase-positive, citrate-positive, urease-positive, and non-motile, distinct from E. coli and Klebsiella. It undergoes mixed-acid fermentation and does not produce indole. Salmonella spp. is coagulase-negative, catalase-positive, citrate-positive, and motile, with a negative urease test. Like S. aureus, it undergoes mixed-acid fermentation but does not produce indole. Overall, the tests for citrate, coagulase, and motility, along with indole and urease results, help to differentiate between these organisms.
Antibacterial activity of various concentrations of crude plant extracts on test organisms
Table 3 presents the effects of different concentrations of three plant extracts on four bacterial species. At 25–100 mg/ml concentrations, extracts of the 3 plant species were active against the bacteria as shown by zones of inhibition ranging from 2.6 mm to 17.6 mm. For instance, at 25 mg/ml, only Chromolaena odorata extract was active against E. coli. However, when the concentration was doubled to 50 mg/ml concentration, the same C. odorata extract was active against E. coli, S. aureus, and Salmonella as in the case of Cymbopogon citratus (C. citratus) and Vernonia amygdalina (V. amygdalina) extracts against E. coli and Klebsiella spp. respectively. At 75 mg/ml concentration, all three plant species extracts were active against E. coli and Klebsiella spp. while only C. odorata extracts were active against S. aureus and Salmonella. Furthermore, all three plant species extracts were active against all four bacteria at 100 mg/ml concentration, with zones of inhibition ranging from 5.2 mm to 17.6 mm. Overall, there is a clear pattern in which increasing concentrations (25–100 mg/ml) of extracts has resulted in raised antibacterial activity and vice versa.
Comparative activities of medicinal plant extracts and commercial antibiotics on E. coli
Table 4 compares the antibacterial activity of three plant species extracts and those of 10 commercial antibiotics on E. coli. Across 25–100 mg/ml concentrations, extracts of the three (3) plant species were found to be active against E. coli as shown by zones of inhibition ranging from 2.1 mm to 14.1 mm. In contrast, none of the antibiotics was active against the bacterial strain at 25–75 mg/ml concentrations except at 100 mg/ml. Both plant extracts of all plant species and antibiotics were active against the bacterial strain at 100 mg/ml concentration although antibacterial activities of all plant species (10.3–14.1 mm) were higher than those of eight or nine antibiotics (4–15 mm).
Table 4.
Comparative activities of medicinal plant extracts and commercial antibiotics on E. Coli.
| Zones of Inhibition by Concentration (mg/ml) | ||||
|---|---|---|---|---|
| Extract | 25 | 50 | 75 | 100 |
| A | - | 4.24 ± 0.71 | 11.53 ± 0.45 | 12.35 ± 0.31 |
| B | - | - | 3.76 ± 0.26 | 14.10 ± 0.25 |
| C | 3.56 ± 0.24 | 4.5 ± 0.56 | 2.14 ± 0.64 | 10.30 ± 0.62 |
| Antibiotics | ||||
| PEF | - | - | - | 10 |
| CN | - | - | - | 12 |
| CH | - | - | - | 4 |
| SP | - | - | - | 7 |
| AMX | - | - | - | 6 |
| AU | - | - | - | 10 |
| CPX | - | - | - | 15 |
| S | - | - | - | 4 |
| SXT | - | - | - | 6 |
| T | - | - | - | 4 |
SXT = Septrin (30 µg); CN = Gentamycin (10 µg), CPX = Ciprofloxacin, S = Streptomycin (30 µg), CH = Chloramphenicol (30 µg), SP = Sparfloxacin (10 µg), AM = Amoxicillin (30 µg), AU = Augmentin (10 µg), PEF = Pefloxacin (30 µg), T = Tarivid (10 µg). A = Lemon grass leaf extract B = Bitter leaf extract C = Awolowo leaf extract.
Comparative activities of medicinal plant extracts and commercial antibiotics onKlebsiella spp
Table 5 compares the antimicrobial effects of three plant extracts and commercial antibiotics on Klebsiella spp. At 25–100 mg/ml concentrations, extracts of 1–3 plant species were active against the test bacterial strain (2.7–17.6 mm zones of inhibition) while all antibiotics were active (2–10 mm) only at 100 mg/ml concentration (not at 25–75 mg/ml). At 100 mg/ml concentration, extracts of all plant species yielded zones of inhibition (15.2–17.6 mm) or antibacterial activities that were by far higher than those of all antibiotics (2–10 mm).
Table 5.
Comparative activities of medicinal plant extracts and commercial antibiotics on Klebsiella spp.
| Zones of Inhibition by Concentration (mg/ml) | ||||
|---|---|---|---|---|
| Extract | 25 | 50 | 75 | 100 |
| A | - | 4.24 ± 0.71 | 11.53 ± 0.45 | 12.35 ± 0.31 |
| B | - | - | 3.76 ± 0.26 | 14.10 ± 0.25 |
| C | 3.56 ± 0.24 | 4.5 ± 0.56 | 2.14 ± 0.64 | 10.30 ± 0.62 |
| Antibiotics | ||||
| PEF | - | - | - | 7 |
| CN | - | - | - | 10 |
| CH | - | - | - | 8 |
| SP | - | - | - | - |
| AMX | - | - | - | - |
| AU | - | - | - | - |
| CPX | - | - | - | 9 |
| S | - | - | - | 4 |
| SXT | - | - | - | 2 |
| T | - | - | - | 4 |
SXT = Septrin (30 µg); CN = Gentamycin (10 µg), CPX = Ciprofloxacin; S = Streptomycin (30 µg), CH = Chloramphenicol (30 µg), SP = Sparfloxacin (10 µg), AM = Amoxicillin (30 µg), AU = Augmentin (10 µg), PEF = Pefloxacin (30 µg), T = Tarivid (10 µg). A = Lemon grass leaf extract: B = Bitter leaf extract: C = Awolowo leaf extract.
Comparative activities of medicinal plant extracts and commercial antibiotics on Salmonella spp
Table 6 compares the effects of three plant extracts (Lemongrass, Bitter leaf, and Awolowo leaf) and 10 commercial antibiotics on Salmonella spp. At 25 mg/ml concentrations, neither the extracts nor the antibiotics were active against Salmonella spp. However, at 50 and 75 mg/ml concentrations only C. odorata extracts exhibited activity against the strain while none of the antibiotics was active. Nonetheless, at 100 mg/ml concentration, both plant extracts of all three species and antibiotics were active against Salmonella spp. The zone of inhibition (11.8 mm) or antibacterial activity of C. odorata at 100 mg/ml concentration was higher than those of eight antibiotics. The respective zones of inhibition of C. citratus and V. amygdalina extract at 100 mg/ml concentration were slightly higher than those of four antibiotics.
Table 6.
Comparative activities of medicinal plant extracts and commercial antibiotics on Salmonella spp.
| Zones of Inhibition by Concentration | ||||
|---|---|---|---|---|
| Extract | 25 | 50 | 75 | 100 |
| A | - | - | 5.20 ± 0.84 | |
| B | - | - | 5.4 ± 0.8 | |
| C | - | 4.21 ± 0.35 | 5.64 ± 0.3 | 11.82 ± 0.32 |
| Antibiotics | ||||
| PEF | - | - | - | 12 |
| CN | - | - | - | 8 |
| A | - | - | - | 8 |
| Z | - | - | - | 4 |
| AMX | - | - | - | 10 |
| R | - | - | - | 8 |
| CPX | - | - | - | 14 |
| S | - | - | - | 4 |
| SXT | - | - | - | 2 |
| E | - | - | - | 5 |
PEF = Pefloxacin (10 µg); CN = Gentamycin (10 µg); A = Ampiclox (30 µg); Z = Zinnacef (20 µg), AMX = Amoxicillin (30 µg), R = Rocephin (25 µg), CPX = Ciprofloxacin, S = Streptomycin (30 µg), SXT = Septrin (30 µg) and E = Erythromycin (10 µg).
Comparative activities of medicinal plant extracts and commercial antibiotics on S. aureus
Table 7 compares the antimicrobial effects of Lemongrass, Bitter Leaf, Awolowo Leaf, and 10 commercial antibiotics against Staphylococcus aureus. At 50–100 mg/ml, extracts from 1 to 3 plants showed activity, while antibiotics were only effective at 100 mg/ml, with no activity observed at 25–75 mg/ml. At 100 mg/ml, all plant extracts and antibiotics exhibited activity against S. aureus. Notably, the C. odorata extract produced a larger inhibition zone (11 mm) than eight antibiotics, while the inhibition zones of C. citratus (4.2 mm) and V. amygdalina (6.5 mm) were greater than those of three to four antibiotics (2–6 mm).
Table 7.
Comparison of results obtained from medicinal plant extracts and commercial antibiotics on S. Aureus.
| Concentration | ||||
|---|---|---|---|---|
| Extract | 25 | 50 | 75 | 100 |
| A | - | - | 3.78 ± 0.9 | 4.23 ± 0.84 |
| B | - | - | 6.54 ± 0.52 | |
| C | - | 4.65 ± 0.35 | 5.00 ± 98 | 11.03 ± 0.86 |
| Antibiotics | ||||
| PEF | - | - | - | 10 |
| CN | - | - | - | 12 |
| A | - | - | - | 8 |
| Z | - | - | - | 6 |
| AMX | - | - | - | 10 |
| R | - | - | - | 8 |
| CPX | - | - | - | 14 |
| S | - | - | - | 4 |
| SXT | - | - | - | 2 |
| E | - | - | - | 4 |
PEF = Pefloxacin (10 µg), CN = Gentamycin (10 µg); A = Ampiclox (30 µg); Z = Zinnacef (20 µg), AMX = Amoxicillin (30 µg); R = Rocephin (25 µg); CPX = Ciprofloxacin; S = Streptomycin (30 µg), SXT = Septrin (30 µg) and E = Erythromycin (10 µg).
Discussion
This study evaluated the therapeutic potential of extracts from three plant species: Vernonia amygdalina, Cymbopogon citratus, and Chromolaena odorata against clinically pathogenic bacterial strains, including Escherichia coli, Klebsiella spp., Salmonella spp., and Staphylococcus aureus. Results demonstrated significant antibacterial activity, highlighting the plants’ extracts or phytocomponents’ potential as alternative or complementary antimicrobial agents.
Comparative efficacy of plant extracts and commercial antibiotics
The plant extracts demonstrated varying but broad-spectrum antibacterial activity, with V. amygdalina exhibiting the widest zone of inhibition (14 mm) against E.coliand Klebsiella spp. A similar activity has been reported in literatures12–16 Chromolaena odorata also consistently inhibited E. coli, Klebsiella spp., Salmonella spp., and S. aureus surpassing more than seven commercial antibiotics like Amoxicillin, Erythromycin, and Streptomycin. These findings align with prior studies that attribute the antibacterial activity of C. odoratato bioactive compounds11,17–23. However, Ciprofloxacin and Gentamycin still exhibited good antibacterial activity, reaffirming the efficacy of conventional antibiotics against multidrug-resistant bacteria while highlighting the complementary potential of the plants’ phytocomponents.
Concentration dependent activity
While all extracts exhibited promising therapeutic potentials, their antibacterial activities were concentration-dependent, with higher concentrations (75–100 mg/ml) yielding significantly better inhibition aligning with the findings of Magaji et al.24. This trend underscores the importance of dosage optimization to maximize the therapeutic efficacy of plant-derived antimicrobials25–27. For instance, while Vernonia amygdalina, Cymbopogon citratus, and Chromolaena odorataexhibited moderate activity at lower concentrations, their efficacy improved markedly at 100 mg/ml. The presence of bioactive compounds in these plants likely contributed to the antibacterial effects, though these compounds may require higher concentrations to exert meaningful inhibition28,29.
Species specific activity
Among the tested bacteria, E. coli and Klebsiella spp. were particularly susceptible to V. amygdalina extracts, with inhibition zones (14 mm) that exceeded those of all commercial antibiotics except ciprofloxacin (15 mm). This activity suggests that V. amygdalinacontains potent bioactive compounds capable of disrupting gram-negative bacterial structures, possibly targeting their outer membrane or interfering with essential metabolic pathways30,31. Similarly, C. odorata plant extract was more active against Salmonella spp. and S. aureus, with significant efficacy observed only at higher concentrations (50–100 mg/ml) and corroborated by Stanley et al.32, and Ameen et al.33. These findings may be due to differences in bacterial physiology, including variations in cell wall composition, efflux pump mechanisms, or intrinsic resistance genes. Moreover, we observed that all plant extracts across the different concentrations (25–100 mg/ml) demonstrated the least activity against S. aureus, a gram-positive bacterium, aligning with established knowledge of its structural defenses; the thick peptidoglycan layer of gram-positive bacteria presents a formidable barrier to the passage of antimicrobial agents34,35. Despite the thick peptidoglycan layer, the higher activity of C. odorata extracts at 100 mg/ml suggests that increased concentrations overcome these structural defenses. This concentration-dependent efficacy highlights the importance of optimizing dosage in the formulation of plant-based antimicrobial agents to maximize their therapeutic potential.
Mechanisms of antibacterial action
The observed antibacterial activities of these plant extracts are likely due to the presence of secondary metabolites such as flavonoids, alkaloids, tannins, and saponins, which can inhibit microbial growth through mechanisms like cell membrane disruption, enzyme inhibition, and interference with DNA synthesis36–38. For example, literature has confirmed the presence of alkaloids, tannins, flavonoids, steroids, saponins, phenolic acids, xanthones, anthraquinones, cyanogenic glycosides, terpenoids, coumarins, edotides, and sesquiterpenes in Vernonia amydalina39,40. Similarly, Akinmoladun et al.41 reported a positive test for the presence of alkaloids tannins, steroids, terpenoids, flavonoids, and cardiac glycosides in aqueous and methanolic extracts of C. odorataleaves. Cymbopogon citratus has not been left out of phytochemistry and pharmacological studies as several studies have established the presence of flavonoids, essential oils, and phenolic compounds42,43all of which have demonstrated varying degrees of antimicrobial activities44–46.
Conclusion
Our study observed that the efficacy of the medicinal plants against bacterial species across all concentrations was higher than that of many antibiotics. This finding has proven that some or all those medicinal plant species could be used as alternative or complementary therapeutics to address antibiotic resistance. However, since the findings were based on an in-vitro study, we recommend clinical trials to establish safe and effective doses of those plant extracts in humans.
Abbreviations
- E.coli
Escherichia coli
- S.aureus
Staphylococcus aureus
- mg
Milligram
- ml
Milliliter
- Spp
Specie
Author contributions
UJU: Conceptualization, methodology, resources, writing-initial draft drafting.EA: Conceptualization, methodology, supervision, writing -review and editing, validation.ACO: Experimentation, data analysis, Writing - review and editingEAE: Methodology, data curation, Writing - review and editing, validation, visualizationDM: data analysis, methodology, visualization AEO: Methodology, data curation, Writing - review and editing, validation, visualizationPT: Conceptualization, methodology, supervision, writing- review and editing, validation.
Funding
This study was not funded.
Data availability
Data used for the development of this manuscript have been presented within the manuscript.
Declarations
Competing interests
The authors declare no competing interests.
Ethics approval and consent to participate
Ethical approval was not required for this study.
Consent for publication
Not required for this study however all authors have read and approved this final draft for submission.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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