J. Microbiol. Infect. Dis., (2026), Vol. 16(2): 93–100

Research Article

10.5455/JMID.2026.v16.i2.5

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Comparative antibacterial effects of aqueous, methanol, and acetone extracts of Ocimum gratissimum scent leaf on gastrointestinal bacteria

Vivian Nkemkanma Agi^* and Jane Nyele Agbolu

Department of Medical Microbiology, Faculty of Medical Laboratory Science, Rivers State University, Port Harcourt, Nigeria

*Corresponding Author: Vivian Nkemkanma Agi. Department of Medical Microbiology, Faculty of Medical Laboratory Science, Rivers State University, Port Harcourt, Nigeria. Email: nyelejane [at] gmail.com, von73vv22 [at] yahoo.com

Submitted: 05/10/2025 Revised: 30/03/2026 Accepted: 09/04/2026 Published: 17/05/2026

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ABSTRACT

Background: The increasing prevalence of antibiotic resistance and associated adverse reactions has prompted the search for alternative antimicrobial agents, including medicinal plant extracts, to be developed.

Aim: In this study, we evaluated the in vitro antibacterial activity and minimum inhibitory concentration (MIC) of Ocimum gratissimum (scent leaf) extracts against selected gastrointestinal bacterial isolates.

Methods: Fresh scent leaves were collected from the Rivers State University farm, dried for 2 weeks, and ground into powder. Methanolic and acetonic extracts were prepared from dried leaves, whereas aqueous extracts were obtained from fresh leaves. The extracts were tested against Escherichia coli, Enterococcus spp., Klebsiella spp., and Proteus spp. (n=3 isolates per species). The antibacterial activity was assessed using the agar well diffusion method at concentrations of 250, 187.5, 125, and 62.5 mg/ml. Dimethyl sulfoxide and sterile distilled water were used as negative controls, and ciprofloxacin (10 µg) was used as a positive control. All assays were performed in triplicate, and the results are expressed as mean ± standard deviation. MIC values were determined using the broth microdilution method. Data were analyzed using two-way ANOVA followed by Tukey’s HSD post hoc test, with significance set at p < 0.05.

Results: Results on the antibacterial activity of O. gratissimum methanolic extracts at various concentrations (250, 187.5, 125, and 62.5 mg/ml) revealed the highest zone of inhibition millimeters (mm) in Klebsiella species (29 ± 1.00), followed by Enterococcus species (21 ± 0.00), while E. coli was (19 ± 0.00) and Proteus species (19 ± 0.50). Ocimum gratissimum acetonic extracts at different concentrations (250, 187.5, 125, and 62.5 mg/ml) revealed the highest zone of inhibition (mm) in Enterococcus species (22 ± 1.00), followed by Proteus species (20 ± 0.50), Klebsiella species (18 ± 1.00), and E. coli (15 ± 0.50). In contrast, O. gratissimum aqueous extracts at different concentrations (250, 187.5, 125, and 62.5 mg/ml) showed no zones of inhibition (0 ± 0.00). The MICs of the methanolic and acetonic extracts ranged from 62.5–187.5 mg/ml, depending on the bacterial species, whereas aqueous extracts showed no inhibition. A significant interaction between extract concentration and bacterial species was observed (p < 0.05).

Conclusion: Methanolic and acetonic O. gratissimum extracts exhibit in vitro antibacterial activity against selected gastrointestinal bacteria, whereas the aqueous extract showed no activity. However, these results are preliminary and are based on crude extracts tested at relatively high concentrations. Further studies are required to isolate active compounds, evaluate their safety, and assess their in vivo efficacy before clinical application.

Keywords: Antibacterial activity, Antibiotic resistance, Gastrointestinal bacteria, Ocimum gratissimum, Plant extracts.

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Introduction

As many pathogenic bacteria no longer respond effectively to commonly used antimicrobial drugs, antibiotic resistance has become a major global health concern. Furthermore, the frequent adverse effects associated with several synthetic antibiotics limit their safe and prolonged use. These challenges have reduced the effectiveness of conventional antimicrobial therapy and increased the need for alternative treatment options. Medicinal plants have therefore attracted attention as sources of natural antimicrobial agents due to their bioactive secondary metabolites (Yuan et al., 2016). However, concerns remain regarding their safety, availability, preservation, and scientific validation, as only a limited number of medicinal plants have been adequately laboratory tested and clinically monitored (Ekor, 2014; Awodele et al., 2018; Imosemi, 2020).

Nevertheless, herbal plants used in traditional medicine and therapy have a lower risk compared to synthetic drugs because of their history of use in disease treatment (Zhang et al., 2015). The World Health Organization (WHO, 2019) reported that herbal or traditional medicine is not only effective in the treatment of diseases (including chronic ones) but also improves mental health and quality of life in the aging population (WHO, 2019).

The Ocimum gratissimum, commonly known as the scent leaf, has been named as one of the medicinal plants with the potential to serve as an effective alternative therapy for the treatment of some ailments or as a new drug source. It is a common and commercially viable perennial herbaceous plant with a strong minty aroma. It is used as a natural flavoring agent, condiment, or vegetable in soup, stew, and protein sauce preparation. It is also used in traditional medicine for the treatment of several ailments, such as cough, pneumonia, fever, swelling, anemia, diarrhea, pain, and fungal, bacterial, and viral infections (Pandey, 2017; Bhavani et al., 2019; Hamma et al., 2020; Ugbogu et al., 2021; Bhattacharya et al., 2024).

Several studies have reported the antibacterial activity of Ocimum species against various pathogenic microorganisms. Extracts of O. gratissimum, Ocimum basilicum, and Ocimum sanctum inhibit both gram-positive and gram-negative bacteria, including Escherichia coli, Staphylococcus aureus, Salmonella spp., and Klebsiella spp. (Marcelline et al., 2020; Dharsono et al., 2022). Pathogenic gastrointestinal bacteria are responsible for gastroenteritis, an infection/inflammation of the digestive tract commonly acquired through contaminated food and water. Bacterial agents, such as E. coli, Salmonella spp., and Shigella spp., Campylobacter spp., and S. aureus are known causes of gastroenteritis, presenting with diarrhea, abdominal cramps, fever, headache, bloody stools, bloating, lethargy, and body aches (Ohkusa et al., 2023; Agi and Mbata, 2025). Diarrheal diseases remain a significant public health challenge, particularly in developing countries, and are reported as the second leading cause of death among children aged 5 years, accounting for approximately 760,000 deaths annually (Chimnoi et al., 2018). Malnourished children, immunocompromised individuals, and people living with HIV are particularly vulnerable to life-threatening diarrheal infections.

Although previous studies have shown that O. gratissimum has antibacterial activity, research evaluating its effects using different solvents and standard minimum inhibitory concentration (MIC) testing against important gastrointestinal bacteria is limited. Methanol and acetone were used because they can extract various bioactive compounds, such as flavonoids, alkaloids, and essential oils. Water was also used to mimic traditional herbal preparations. The tested extract concentrations (250, 187.5, 125, and 62.5 mg/ml) were selected based on preliminary tests and previous studies showing antibacterial activity at these concentrations.

Bacterial species chosen for this study—E. coli, Proteus spp., and Enterococcus spp., and Klebsiella spp.—are common gastrointestinal pathogens that are increasingly resistant to multiple antibiotics, making them important targets for alternative treatments. The antibacterial activity was evaluated using the agar well diffusion method, and the MIC was measured using the broth microdilution method according to the Clinical and Laboratory Standards Institute guidelines (CLSI, 2024).

Given the rising incidence of multidrug-resistant gastrointestinal pathogens and the increasing adverse effects associated with synthetic antibiotics, there is an urgent need to explore the therapeutic potential of plant-based antimicrobial agents. Therefore, O. gratissimum presents a promising natural alternative, and this study was designed to evaluate the antibacterial activity of its extracts against selected gastrointestinal bacterial isolates.

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Materials and Methods

Study area

The study was conducted in the Medical Microbiology Laboratory of the Faculty of Medical Laboratory Science, Rivers State University (RSU), Port Harcourt, Republic of the Congo. RSU is a university located in the Mile 3, Diobu area of Port Harcourt, Rivers State, Nigeria. Port Harcourt is the capital of Rivers State, Nigeria. It is located at latitude 4.75⁰N and longitude 7.00⁰E and lies along Bonny River on the Niger Delta and covers an area of 369 km² (Fig. 1).

Collection and preparation of plants

Fresh samples of O. gratissimum scent leaves were collected on September 20, 2025, from the RSU farm. The plant was identified and confirmed by the Department of Biology, RSU (voucher specimen number RSU/Og-001). The fresh leaves were washed and dried completely at room temperature for 2 weeks. The dried leaves were crushed into powder form using an electric grinder.

Plant extraction method

Crushed scent leaf (O. gratissimum) powder (10 g) was measured into a conical flask. Extraction was performed by adding 40 ml of solvents (methanol and acetone) and water for fresh leaves and heating at 40^oC for 48 hours, stirring intermittently every 6 hours. Extraction at 40°C was selected to enhance solvent penetration and extraction efficiency while minimizing the degradation of thermolabile phytochemicals. This temperature is moderate enough to preserve most bioactive compounds in plant materials. The mixtures were filtered through Whatman No. 1 filter paper, and the filtrates were evaporated to dryness using a water bath to obtain solid extracts (Agholor et al., 2018). Each extraction was performed in triplicate, and the yields were expressed as % w/w of the starting plant material. A dark green solid extract of O. gratissimum was sealed in an airtight container at 4°C for further analysis.

Reconstitution of the plant extract

The methanol and acetone plant extracts were reconstituted in dimethyl sulphoxide (DMSO) and water for the aqueous extract, respectively, to yield the subsequent concentrations of the extract. Serial dilutions were performed to obtain final concentrations of 250, 187.5, 125, and 62.5 mg/ml. The final DMSO concentration in all assays was 1% (v/v), and DMSO-only controls were included to account for any solvent effect on bacterial growth.

Figure 1. Map of Port Harcourt showing RSU (Google Maps, 2024).

Collection and confirmation of the test organisms

Pure clinical isolates of E. coli, Proteus spp., Enterococcus spp., and Klebsiella spp. were obtained from the stock culture collection of the RSU Teaching Hospital, where they had been previously identified using standard clinical microbiological procedures. In this study, the isolates were reconfirmed using Gram staining and CHROMagar for differential identification and purity assessment before testing. These methods were employed as preliminary confirmation techniques to ensure the consistency of colony morphology and Gram reaction. However, more advanced identification methods, such as biochemical profiling or molecular techniques, could provide higher specificity. Isolates were maintained on appropriate media at 4°C until use.

Ethical approval

Ethical approval was not required because no human subjects were directly involved.

Antibacterial susceptibility assay

Agar well diffusion

The antibacterial activity of the plant extracts was evaluated using the agar well diffusion assay. Using a sterile cork borer, wells measuring approximately 5 mm in diameter were aseptically prepared in the agar surface, and these wells were designated with labels corresponding to the respective plant extract concentrations (250, 187.5, 125, and 62.5 mg/ml). The wells were then filled with 100 µl of extract solution, and the plates were incubated at 37°C for 24 hours. DMSO (1% v/v) served as the negative control while ciprofloxacin (10 µg) was used as the positive control, as described by Agholor et al. (2018). Zones of inhibition were measured in millimeters (mm) after incubation. The results obtained for the plant extracts were recorded descriptively, as there are no established CLSI interpretive criteria for crude plant extracts. The CLSI guidelines were applied only in the interpretation of standard antibiotic susceptibility testing where applicable.

Determination of MIC

The MIC of O. gratissimum extracts was determined using the broth microdilution method in accordance with standard microbiological procedures. Methanolic, acetone, and aqueous extracts were reconstituted in DMSO or sterile distilled water and serially diluted to obtain concentrations of 250, 187.5, 125, and 62.5 mg/ml, respectively. Standardized bacterial inocula equivalent to approximately 5 × 10⁵ CFU/ml of E. coli, Proteus spp., Enterococcus spp., and Klebsiella spp. were prepared and added to each dilution. All tests were performed in triplicate. Appropriate controls were included: a positive control (broth containing bacterial inoculum without extract), a negative control (sterile broth only), and a solvent control (broth containing extract solvent without plant extract). Microdilution plates were incubated at 37°C for 18–24 hours. The MIC was defined as the lowest concentration of the extract that showed no visible bacterial growth after incubation. For Enterococcus spp. and Klebsiella spp., additional serial dilutions below 62.5 mg/ml were further prepared and tested due to continued inhibition observed at the lowest initial concentration.

Statistical analysis

All experiments were performed in triplicate, and the results were expressed as mean ± standard deviation. The zones of inhibition (mm), treated as continuous variables, were analyzed using two-way analysis of variance to evaluate the effects of extract concentration and bacterial species, as well as their interaction. Where significant differences were observed, post hoc multiple comparisons were performed using Tukey’s honestly significant difference test to identify specific group differences. Statistical significance was set at p < 0.05. All statistical analyses were performed using the Statistical Package for the Social Sciences version 25.

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Results

Table 1 presents the morphological and biochemical characteristics of the bacterial isolates. Identification was based on the Gram reaction, cellular morphology, and standard biochemical tests. Escherichia coli, Proteus spp., and Klebsiella spp. were identified as gram-negative rods, whereas Enterococcus spp. appeared as gram-positive cocci arranged in pairs or short chains. Motility testing revealed that E. coli and Proteus spp. were motile, whereas Klebsiella spp. and Enterococcus spp. were nonmotile. The isolates also exhibited characteristic biochemical reactions. Escherichia coli was indole positive and citrate negative, whereas Klebsiella spp. was citrate positive and indole negative. Proteus spp. demonstrated urease activity and variable indole reactions, whereas Enterococcus spp. was catalase-negative. CHROMagar differentiation further supported the identification of the isolates based on colony color characteristics. Escherichia coli had a pinkish to red coloration, Proteus spp. appeared colorless, and Klebsiella spp. had a metallic blue color, while Enterococcus spp. appeared as blue colonies. These findings are consistent with the standard microbiological identification criteria for the respective bacterial species.

Table 2 shows the antibacterial activity of O. gratissimum methanolic extract at concentrations of 250, 187.5, 125, and 62.5 mg/ml The highest zone of inhibition was observed in Klebsiella spp. (29 ± 1.00 mm), followed by Enterococcus spp. (21 ± 0.00 mm), while E. coli and Proteus spp. showed zones of 19 ± 0.00 and 19 ± 0.50 mm, respectively, at the highest concentration tested. The inhibition zones decreased with decreasing extract concentration, indicating a concentration-dependent antibacterial effect. One-way ANOVA revealed that the differences in inhibition zones across concentrations were statistically significant for all isolates (p < 0.05).

Table 3 presents the antibacterial activity of the O. gratissimum acetone extract at varying concentrations (250, 187.5, 125, and 62.5 mg/ml). The highest zone of inhibition was recorded for Enterococcus spp. (22 ± 1.00 mm), followed by Proteus spp. (20 ± 0.50 mm), and Klebsiella spp. (18 ± 1.00 mm), and E. coli (15 ± 0.50 mm). A concentration-dependent decrease in antibacterial activity was observed across all isolates. Differences in inhibition zones were statistically significant (p < 0.05, one-way ANOVA).

Table 1. Morphological and biochemical characteristics of the bacterial isolates.

Table 2. Mean ± standard deviation (mm) of zones of inhibition of O. gratissimum methanolic extract against tested bacterial isolates.

Table 3. Mean ± standard deviation (mm) of zones of inhibition of O. gratissimum acetonic extract against tested bacterial isolates.

Table 4. Mean ± standard deviation (mm) of zones of inhibition of aqueous O. gratissimum extract against tested bacterial isolates.

Table 4 below shows the antibacterial activity of aqueous extracts of Scent Leaves (O. gratissimum) at varying concentrations (250, 187.5, 125, and 62.5 mg/ml). From the table, all bacterial isolates showed resistance at the different concentrations(0 ± 0.00 mm). As there was no variation in the data, statistical analysis was not applicable.

Table 5 shows the MIC of the methanolic, acetonic, and aqueous O. gratissimum extracts against the test organisms. The methanolic extract exhibited an MIC of 125 and 62.5 mg/ml against E. coli and 62.5 mg/ml against Proteus spp., respectively, indicating moderate antibacterial activity. Acetonic extract demonstrated higher activity against Enterococcus spp. and Klebsiella spp., with a MIC of 62.5 mg/ml for both organisms. In contrast, the aqueous extract showed no inhibitory activity at any of the tested concentrations; therefore, the MIC could not be determined. These results indicate that O. gratissimum’s antibacterial potency is both solvent-dependent and organism-specific, with organic solvents (methanol and acetone) extracting more active compounds than water.

Table 5. MIC values of methanolic, acetonic, and aqueous extracts against test organisms.

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Discussion

The results showed that methanolic and acetonic extracts of scent leaf (O. gratissimum) exhibited antibacterial activity against the tested bacteria, whereas the aqueous extract showed no observable activity at the concentrations used. The variation in activity among the extracts may be attributed to the type of extraction solvent used. Methanol and acetone, being organic solvents, extract a wider range of bioactive compounds than water. These solvents are capable of dissolving important phytochemicals, such as flavonoids, tannins, alkaloids, and saponins, which have been reported to possess antibacterial properties (Bhavani et al., 2019). The methanolic extract demonstrated the highest antibacterial activity, particularly against Klebsiella spp., followed by Enterococcus spp., E. coli, and Proteus spp. The observed increase in zones of inhibition with increasing concentration indicates a dose-dependent effect, where higher concentrations produced greater antibacterial activity. A similar concentration-dependent trend was observed with the acetonic extract, with Enterococcus spp. showing the highest level of inhibition, followed by Proteus spp., Klebsiella spp., and E. coli. This suggests that the antibacterial efficacy of O. gratissimum is influenced by the extraction solvent and extract concentration. These findings are consistent with those of previous studies. Omodamiro and Jimoh (2015)reported that ethanolic extracts of O. gratissimum at varying concentrations (500, 250, 125, 62.5, and 31 mg/ml) exhibited antibacterial activity against Proteus mirabilis and E. coli in a dose-dependent manner. Similarly, Jesuwenu and Michael (2017)reported inhibition zones of approximately 18 mm for S. aureus and Enterococcus faecalis and up to 31 mm for P. mirabilis. In addition, Ishiwu et al. (2014)demonstrated that increasing the concentration of O. gratissimum extract reduced the viability of E. coli and S. aureus. In contrast, the Aqueous extract showed no zones of inhibition at the tested concentrations. This may be due to water’s limited ability to extract active antibacterial compounds from plant materials. Omojoyegbe et al. (2023)reported similar observations, finding that aqueous extracts exhibited minimal or no activity at lower concentrations but became effective at higher concentrations. This suggests that the bioactive constituents of O. gratissimum can be extracted more efficiently using organic solvents than water. The reduced activity of the aqueous extract may also be attributed to the poor solubility of active compounds or the presence of substances that interfere with antimicrobial activity (Omojoyegbe et al., 2023).

The methanolic and acetonic extracts demonstrated appreciable antibacterial activity against both gram-positive and gram-negative bacteria when compared with standard antibiotics such as ciprofloxacin and gentamicin. This activity may be linked to the presence of phytochemicals that interfere with bacterial cell wall synthesis, protein synthesis, and other essential metabolic processes (Bhavani et al., 2019). The antibacterial activity of the plant extracts in this study was evaluated based on the measurement of zones of inhibition and interpreted descriptively. Unlike standard antibiotics, crude plant extracts do not have established CLSI breakpoints for classification into susceptible or resistant categories. Therefore, the results were not interpreted using CLSI criteria but rather based on relative differences in inhibition zones, which is consistent with the standard practice in phytochemical research. However, despite the notable antibacterial activity of the methanolic extracts of O. gratissimum against the tested organisms, this study has some limitations. The specific phytochemicals responsible for the observed antibacterial activity were not identified, and the MIC values were not determined for all isolates. In addition, the study was limited to a small number of bacterial isolates, which may affect the generalizability of the findings across a wider range of clinical strains. The identification of the test organisms was based on preliminary methods, which, while adequate for basic confirmation, may lack the specificity of advanced techniques. To improve the robustness and reliability of the results, future studies should focus on detailed phytochemical analysis, determination of MIC values, inclusion of a larger number of clinical isolates, and use of advanced identification techniques such as molecular characterization.

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Conclusion

This study suggests that methanolic and acetonic O. gratissimum extracts are effective antibacterial agents, as evidenced by their in vitro efficacy against the isolated bacteria. This could have significant implications for healthcare, providing a basis for further drug development research. Further studies are necessary for phytochemical analysis, toxicity testing, purification of active compounds, and to isolate and characterize the bioactive constituent responsible for the observed effect.

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Acknowledgments

The authors wish to express their sincere gratitude to the Department of Medical Microbiology, RSU, for providing the laboratory facilities used in this study. The authors also appreciate the technical assistance of the laboratory staff and support of colleagues and friends who contributed to the successful completion of this work.

Conflict of interest

The authors declare that there is no conflict of interest.

Funding

This research received no specific grant.

Authors’ contributions

This work was carried out in collaboration among the authors. V.N.A. designed the study, wrote the protocol, and wrote the first draft. Author A.J.N. managed the literature searches and performed the statistical analysis. All authors have read and approved the final manuscript.

Data availability

All relevant data supporting this study’s findings are contained within this manuscript.

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References

Agholor, K., Lucy, M.Y., Idris, A., Lucy, F.O. and Rakiya, Z. 2018. Antibacterial activity of Ocimum gratissimum (scent leaf) on some pathogenic gastrointestinal bacteria. Afr. J. Microbiol. Res. 12(40), 923–929; doi:10.1016/j.ajmr.2018.09.010

Agi, V.N. and Mbata, C.A. 2025. Molecular characterization of enteric bacteria in diarrheal stool samples of children less than five years characterisation of enteric bacteria in diarrhoeic stool samples of children less than five years in Port Harcourt, Nigeria. Microbiol. Res. J. Int. 35(3), 92–105.

Awodele, O., Fajemirokun, O., Oreagba, I., Samuel, T.A., Popoola, T.D., Coulidiaty, A.V. and Emeka, P.M. 2018. Herbal medicines use: remedies or risks. West Afr. J. Pharm. 29(2), 1–18; doi:10.1016/j.wajp.2018.09.007

Bhattacharya, R., Bose, D., Maqsood, Q., Gulia, K. and Khan, A. 2024. Recent advances on the therapeutic potential with Ocimum species against COVID-19: a review. South Afr. J. Bot. 164(164), 188–199.

Bhavani, T., Mohan, R.R., Mounica, C., Nyamisha, J., Krishna, A.G., Prabhavathi, P., Raja, R.R. and Baba, K.H. 2019. Phytochemical screening & antimicrobial activity of Ocimum gratissimum review. J. Pharm. Phytochem. 8(2), 76–79.

Chimnoi, N., Reuk-Ngam, N., Chuysinuan, P., Khlaychan, P., Khunnawutmanotham, N., Chokchaichamnankit, D., Thamniyom, W., Klayraung, S., Mahidol, C. and Techasakul, S. 2018. Characterization of essential oil from Ocimum gratissimum leaves: antibacterial activity and mode of action against selected pathogens of gastroenteritis. Microbial. Pathogenesis. 118, 290–300.

Clinical and Laboratory Standards Institute (CLSI). 2024. Performance standards for antimicrobial susceptibility testing, 34th ed. Washington, DC: CLSI press; pp: 1–416.

Dharsono, H.D.A., Putri, S.A., Kurnia, D., Dudi, D. and Satari, M.H. 2022. Ocimum species: a review on chemical constituents and antibacterial activity. Molecules 27(19), 6350.

Ekor, M. 2014. The growing use of herbal medicines: issues relating to adverse reactions and challenges in monitoring safety. Front. Pharmacol. 4, 177; doi:10.1016/j.fpharm.2014.09.010

Google Maps. 2024. Rivers State University, Port Harcourt, Nigeria. Mountain View, CA: Google LLC. Available via https://www.google.com/maps (Accessed 31 July 2024).

Hamma, I.I., Tafinta, I.Y., Abdulmalik, A., Theophilus, J. and Abubakar, M. 2020. Phytochemical screening and antibacterial activity of the crude extract of scent leaf Ocimum gratissimum on Escherichia coli and Staphylococcus aureus. Asian. Plant. Res. J. 5(2), 1–7.

Imosemi, I.O. 2020. A review of the medicinal values, pharmacological actions, morphological effects and toxicity of Ocimum gratissimum Linn. Eur. J. Pharm. Med. Res. 7(7), 29–40.

Ishiwu, C.N., Umenwanne, C.P., Obiegbuna, J.E. and Uchegbu, N. 2014. _{In vitro} assessment of antibacterial effect of extracts of Ocimum gratissimum and Carica papaya leaves. Int. J. Appl. Sci. Technol. 1(4), 171–177.

Jesuwenu, A. and Michael, O. 2017. Antibacterial activity of Ocimum gratissimum L against some selected human bacterial pathogens. J. Pharm. Res. Int. 20(1), 1–8.

Marcelline, A., Timothée, O.A., Martial, S.V., Aminata, A.O., Armand, K.A. and Claude Ka, L. 2020. _{In vivo} antistaphylococcal activity evaluation of Ocimum gratissimum Linn. (Lamiaceae Linn.(Lamiaceae) ophthalmic ointment. J. Adv. Med. Med. Res. 32(20), 44–57.

Ohkusa, T., Nishikawa, Y. and Sato, N. 2023. Gastrointestinal disorders and intestinal bacteria: advances in research and applications in therapy. Front. Med. 9, 935676; doi:10.1016/j.fmed.2023.935676

Omodamiro, O.D. and Jimoh, M.A. 2015. Antioxidant and antibacterial activities of Ocimum gratissimum. Am. J. Phytomed. Clin. Therapeutics 3(1), 10–19; doi:10.1016/j.ajpt.2015.01.009

Omojoyegbe, R.T., Olatunji, E.O., Okanlawon, T.S. and Adedire, S.A. 2023. Phytochemical and antibacterial activity of Ocimum gratissimun L. against three selected gastrointestinal tract pathogens. Mountain Top Univ. J. Appl. Sci. Technol. 3(13 1), 105–114.

Pandey, S. 2017. Antibacterial and antifungal activities of Ocimum gratissimum L. Int. J. Pharm. Pharm. Sci. 9(12), 26–31.

Ugbogu, O.C., Emmanuel, O., Agi, G.O., Ibe, C., Ekweogu, C.N., Ude, V.C., Uche, M.E., Nnanna, R.O. and Ugbogu, E.A. 2021. A review on the traditional uses, phytochemistry, and pharmacological activities of clove basil (Ocimum gratissimum L.). Heliyon 7(11), e0840.

World Health Organization. 2019. WHO global report on traditional and complementary medicine. Geneva, Switzerland: World Health Organization. Available via https://www.who.int/traditionalcomplementary-integrative-medicine/ (Accessed 13 July 2024)

Yuan , H., Ma, Q., Ye, L. and Piao, G. 2016. The traditional medicine and modern medicine from natural products. Molecules 21, 550–559.

Zhang, J., Onakpoya, I.J., Posadzki, P. and Eddouks, M. 2015. The safety of herbal medicine: from prejudice to evidence. Evidence-Based. Complement. Altern. Med. 18(18), 1–3.