Exploring the antibacterial properties of a traditional South African medicinal plant
Used for generations in African traditional medicine
Effective against both Gram-positive and Gram-negative bacteria
Rigorously tested in laboratory studies
In the heart of South Africa's diverse flora grows Clausena anisata, a remarkable medicinal plant known locally as Iperepesi in Xhosa, Umukambati in Zulu, or more descriptively as "Horsewood" or "Perdepis" in English and Afrikaans respectively 6 7 . While its crushed leaves emit a distinctive scent that gives rise to its less-flattering common names, this unassuming shrub represents a beacon of hope in the global fight against antibiotic-resistant bacteria.
As modern medicine grapples with the escalating crisis of drug-resistant pathogens, traditional knowledge is guiding scientists toward potentially powerful solutions hidden within nature's pharmacy.
For generations, traditional healers across Africa have utilized Clausena anisata to treat a myriad of ailments—from fever and pneumonia to sore throats and sinusitis 6 . Its leaves, bark, wood, and roots have been prepared in various forms to address wounds, aching teeth, malaria, kidney troubles, and even to fumigate newborns for protection 6 . Today, this rich ethnobotanical history is undergoing rigorous scientific scrutiny, with researchers asking a critical question: Can this traditional remedy effectively combat the dangerous bacteria that have learned to resist conventional antibiotics? The answer, emerging from laboratories across South Africa and beyond, appears to be a resounding yes.
Clausena anisata is a hardy, evergreen shrub or small tree that typically grows between 3 to 10 meters tall 2 6 . It features attractive compound leaves that release a strong, aniseed-like aroma when crushed—a characteristic that divides opinion but signals the presence of biologically active compounds.
From May to August, the plant produces sprays of creamy-white flowers that later develop into black berries, much loved by birds 2 6 . The plant thrives in various environments, from the coastal regions of the Western Cape through the Eastern Cape and KwaZulu-Natal to Mpumalanga, and beyond to other tropical and subtropical parts of Africa and Asia 6 .
The traditional applications of Clausena anisata are remarkably diverse. In South Africa, new-born babies are passed through the smoke of burning Clausena wood for purification and protection, while leaf infusions serve as steam baths for treating rheumatism, strengthening the heart, and as a general deodorant and cleanser 6 .
Elsewhere on the continent, it has been used to treat everything from malaria and syphilis to diabetes and insect repellency 3 6 . Modern science is now confirming the wisdom behind these traditional practices.
Phytochemical analysis has revealed that Clausena anisata contains an impressive arsenal of bioactive compounds, including flavonoids, tannins, alkaloids, coumarins, phenols, triterpenes, and saponosides 1 3 . These compounds are more abundant in the leaves than in other parts of the plant 1 , explaining why traditional preparations often favor this part of the shrub.
Interfere with bacterial energy metabolism
Bind to proteins on bacterial cell membranes
Intercalate with bacterial DNA
The essential oils derived from the leaves contain varying dominant compounds depending on the plant's chemotype, with E-anethole, estragole, and sabinene among the most significant 5 .
In 2015, researchers at the University of Fort Hare embarked on a systematic investigation to validate the antibacterial properties of Clausena anisata 7 8 . Their study was particularly significant because it focused specifically on the South African variant of the plant and its traditional use against infections associated with tuberculosis.
The research team, led by Lawal, Grierson, and Afolayan, employed rigorous scientific methodology to test the plant's effectiveness against a panel of ten Gram-positive and Gram-negative bacterial strains 7 8 .
Leaves and stem bark collected from Clausena anisata plants
Prepared extracts using acetone, dichloromethane, and water solvents
Evaluated against pathogenic bacteria including Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa
The findings from this study were compelling. The acetone extract of the leaves demonstrated remarkable activity against both Gram-positive and Gram-negative bacteria, with minimum inhibitory concentration (MIC) values ranging from 0.1 mg/ml to 0.5 mg/ml 7 8 . This broad-spectrum activity is particularly significant in the context of antibiotic resistance, as many conventional antibiotics are effective against only one class of bacteria.
| Bacterial Strain | Acetone Extract (mg/ml) | Dichloromethane Extract (mg/ml) | Aqueous Extract |
|---|---|---|---|
| Staphylococcus aureus | 0.1 | 0.5 | No activity |
| Escherichia coli | 0.5 | 5.0 | No activity |
| Streptococcus pyogenes | 0.1 | 5.0 | No activity |
| Pseudomonas aeruginosa | 0.5 | 5.0 | No activity |
Table 1: Antibacterial Activity of Clausena anisata Leaf Extracts (MIC in mg/ml) 7 8
Interestingly, the aqueous (water) extract of the leaves showed little to no activity against most tested organisms, with the exception of the bark aqueous extract which inhibited Staphylococcus aureus (MIC: 0.5 mg/ml) and Pseudomonas aeruginosa (MIC: 5 mg/ml) 7 8 . This finding has important implications for traditional preparation methods, suggesting that some extraction techniques may be more effective than others.
The antibacterial activity of Clausena anisata isn't attributable to a single compound but rather to the synergistic action of multiple phytochemicals working together 1 3 . Different classes of compounds target bacteria through various mechanisms:
Can bind to proteins on bacterial cell membranes, disrupting their structure and function 3 .
Interfere with energy metabolism in bacterial cells and can damage their genetic material 3 .
Intercalate with bacterial DNA, inhibiting replication and protein synthesis 3 .
Disrupt the bacterial cell membrane, causing leakage of cellular contents and ultimately cell death 5 .
This multi-target approach may explain why bacteria are less likely to develop resistance to plant-based antimicrobials compared to single-target conventional antibiotics. The complex phytochemical mixture in Clausena anisata attacks pathogens on multiple fronts simultaneously, making adaptation far more difficult for the microorganisms.
A 2020 study focusing on oral health found that hydroethanolic extracts of the leaves showed significant activity against cariogenic (cavity-causing) and periodontopathic (gum disease-causing) bacteria 1 .
The extract demonstrated bactericidal and bacteriostatic effects against Aggregatibacter actinomycetemcomitan and Fusobacterium nucleatum, with minimum inhibitory concentrations of 50 mg/ml 1 .
The study authors suggested that these antimicrobial properties could be exploited in the development of novel mouthwashes and other treatments for managing oral infections like periodontitis and tooth decay 1 .
A 2024 investigation into the essential oil of Clausena anisata leaves revealed potent activity against nosocomial (hospital-acquired) infections .
The E-anethole-rich oil (containing 70.77% of this compound) exhibited MIC values ranging from 3.91 to 125 µg/mL against problematic pathogens including Staphylococcus and Klebsiella species—bacteria known for their resistance to multiple antibiotics .
The researchers noted the "bactericidal orientation" of the essential oil (with MIC/MBC ratio < 4), indicating its ability to kill bacteria rather than merely inhibiting their growth .
| Oral Pathogen | Plant Part | MIC (mg/ml) | Effect |
|---|---|---|---|
| Aggregatibacter actinomycetemcomitan | Leaves | 50 | Bactericidal |
| Fusobacterium nucleatum | Leaves | 50 | Bactericidal |
| Streptococcus mutans | Stem bark | >50 | Bacteriostatic |
| Lactobacillus spp. | Stem bark | >50 | Bacteriostatic |
Table 2: Antibacterial Activity of Clausena anisata Against Oral Pathogens 1
The compelling scientific evidence supporting the antibacterial properties of Clausena anisata raises an important question: What's next on the path from traditional remedy to approved therapeutic? The journey involves several critical steps that researchers are currently undertaking.
Must be conducted to ensure the safety of Clausena-based treatments for human use. While traditional use suggests a favorable safety profile, modern pharmaceutical requirements demand rigorous testing.
The mechanistic bases of the antibacterial action need to be fully elucidated at the molecular level to optimize formulations and identify potential synergies with conventional antibiotics.
Will be essential to demonstrate efficacy in human patients. While in vitro studies provide promising indications, the human body presents a more complex environment.
Protocols must be developed to ensure consistent potency and safety. The chemical composition can vary depending on geographic location, season, and plant chemotype 5 .
Clausena anisata represents a promising candidate for developing novel antibacterial agents, especially in the fight against multidrug-resistant bacteria.
Clausena anisata represents a perfect marriage of traditional wisdom and modern scientific validation. The compelling research evidence demonstrating its potent antibacterial activity against a broad spectrum of pathogens—including drug-resistant strains—offers hope in the face of the growing antibiotic resistance crisis.
Centuries of indigenous use provide the foundation for scientific exploration
Rigorous laboratory studies confirm the antibacterial properties
Potential for novel treatments against antibiotic-resistant infections
As research continues to unravel the mysteries of Clausena anisata's therapeutic properties, it serves as a powerful reminder that nature often holds solutions to our most pressing challenges—if we're willing to look and learn.