Exploring how traditional plant medicine could help solve the modern crisis of antibiotic resistance
In the relentless war between humans and pathogenic microbes, our best weapons—antibiotics—are increasingly failing. The rise of antimicrobial resistance poses such a grave threat that the World Health Organization has declared it one of the top ten global public health challenges 2 . As conventional antibiotics lose their effectiveness, scientists are racing to discover new therapeutic options. Where are they looking? Often, the answer lies in returning to nature's pharmacy.
Antimicrobial resistance causes at least 700,000 deaths globally each year, with projections of 10 million annual deaths by 2050 if no action is taken.
Lannea kerstingii has been used in African traditional medicine for generations to treat infections, wounds, and inflammatory conditions.
Enter Lannea kerstingii, a modest tree species native to sub-Saharan Africa that has been used in traditional medicine for generations. Recent scientific investigations have uncovered that this member of the Anacardiaceae family possesses remarkable antimicrobial properties, particularly in its leaves 4 . This article explores how researchers are validating traditional knowledge through modern science, revealing how this unassuming plant might hold keys to addressing one of humanity's most pressing health challenges.
Plants produce a vast array of chemical compounds known as phytochemicals (from the Greek "phyto," meaning plant). While not required for basic plant metabolism, these specialized molecules serve crucial defensive functions, protecting plants from insects, fungi, bacteria, and other environmental threats. When humans consume or extract these compounds, we can benefit from their protective properties.
Plant antimicrobials employ sophisticated strategies to combat pathogens, often differing from conventional antibiotics. Where a typical antibiotic might target a single bacterial process, plant compounds frequently employ multiple mechanisms simultaneously:
Some flavonoids interfere with bacterial protein production, preventing microbial growth and reproduction
Many plant compounds prevent bacteria from forming protective communities (biofilms) that enhance their resistance 2
Certain phytochemicals can disable critical bacterial enzymes, including β-lactamases that would otherwise destroy antibiotics 2
This multi-target approach is particularly valuable against drug-resistant bacteria, as it's much more difficult for microbes to develop resistance against several different attacks simultaneously.
A team of researchers led by Njinga and colleagues set out to scientifically validate the traditional uses of Lannea kerstingii through a systematic investigation of its antimicrobial potential 4 . Their approach followed a well-established pathway in natural product research:
Fresh leaves of Lannea kerstingii were collected, identified, and dried using methods that preserve chemical integrity
Dried plant material was ground and subjected to sequential extraction using solvents of increasing polarity (chloroform, ethyl acetate, acetone, and methanol)
Each fraction was quantitatively analyzed for specific phytochemical groups
The extracts were tested against various pathogenic bacteria and fungi using standardized laboratory methods
This systematic approach allowed the researchers to determine not only whether the plant had antimicrobial properties, but also which components were most active and against which specific microorganisms.
The investigation yielded compelling evidence supporting the traditional use of Lannea kerstingii. The table below summarizes the phytochemical composition found in the leaf extracts:
| Fraction | Total Phenolics (mg/g gallic acid) | Total Flavonoids (mg/g quercetin) | Alkaloids (%) | Steroids |
|---|---|---|---|---|
| Chloroform | Not detected | Not detected | 11.0 | Present |
| Ethyl Acetate | 0.67 | 0.67 | Not detected | Not detected |
| Acetone | 0.43 | 0.43 | Not detected | Not detected |
| Methanol | 0.52 | 0.52 | Not detected | Not detected |
The antimicrobial testing revealed even more exciting results. The ethyl acetate fraction demonstrated significant activity against most tested microorganisms, with inhibition zones ranging from 13±0.02 to 29±0.1 mm 4 . The acetone fraction showed selective activity, working only against T. mentagrophytes, while the methanol fraction showed no antimicrobial activity in this particular study.
Perhaps the most significant finding emerged when researchers isolated a specific compound from Lannea kerstingii identified as β-sitosterol-3-O-glucoside . This isolated compound demonstrated impressive broad-spectrum antimicrobial activity, as shown in the table below:
| Microorganism | Zone of Inhibition (mm) | MIC (μg/ml) | MBC/MFC (μg/ml) |
|---|---|---|---|
| S. aureus | 34 | 25 | 50 |
| Methicillin-Resistant S. aureus MRSA | 30 | 25 | 50 |
| E. coli | 24 | 50 | 100 |
| K. pneumoniae | 26 | 50 | 100 |
| S. typhi | 28 | 50 | 100 |
| C. albicans | 26 | 50 | 200 |
| C. tropicalis | 24 | 50 | 200 |
| P. aeruginosa | No activity | ||
| C. krusei | No activity | ||
MIC = Minimum Inhibitory Concentration; MBC = Minimum Bactericidal Concentration; MFC = Minimum Fungicidal Concentration
Studying plant antimicrobials requires specialized techniques and reagents. The table below highlights key tools and methods used in this research:
| Tool/Technique | Primary Function | Specific Example |
|---|---|---|
| Sequential Solvent Extraction | Extract different compound classes based on polarity | Chloroform, ethyl acetate, acetone, methanol fractions |
| Chromatography Techniques | Separate and isolate individual compounds | Dry vacuum liquid chromatography, TLC monitoring |
| Spectroscopic Analysis | Identify chemical structure of compounds | ¹H NMR and ¹³C NMR spectroscopy |
| Antimicrobial Susceptibility Testing | Measure activity against pathogens | Agar diffusion method, broth dilution |
| Quantitative Phytochemical Assays | Measure specific compound groups | Total flavonoid, phenolic, and alkaloid content |
Plant research presents unique challenges that require specialized approaches. The tough cell walls of plant tissues often require mechanical disruption or enzymatic treatments to access internal contents. Additionally, plants contain compounds like polysaccharides and polyphenols that can interfere with analysis, requiring specialized extraction methods 3 . Modern kits have been developed to address these challenges, using silica-based columns or modified CTAB methods to efficiently extract plant DNA and RNA while removing contaminants 3 9 .
Standardizing extraction methods and ensuring compound stability are key hurdles in phytochemical research.
The promising results from Lannea kerstingii are part of a much larger trend in the search for novel antimicrobials. Bibliometric analysis reveals a significant increase in research output on plant antimicrobial compounds, with an impressive average annual growth rate of 13.84% over the past two decades 8 . China and the United States lead this research charge, followed by Brazil and India 8 .
This global research effort is exploring numerous avenues for utilizing plant antimicrobials:
Using plant extracts or purified compounds as primary treatments for infections
Combining plant compounds with conventional antibiotics to enhance their effectiveness
Using plant compounds to disable resistance mechanisms in bacteria
While the research on Lannea kerstingii is promising, significant work remains before compounds from this plant might become available as standardized treatments. Future research needs to focus on:
Beyond β-sitosterol-3-O-glucoside, there may be other potent antimicrobial compounds in L. kerstingii that work synergistically.
Precise molecular targets and pathways affected by the plant's compounds need to be elucidated at the cellular level.
Toxicity and safety profiles must be established through rigorous animal model testing before human trials.
Research should investigate how L. kerstingii compounds interact with conventional antibiotics for combination therapies.
Consistent extraction methods and quality control measures are needed for reproducible results.
"Phytochemicals are generally less expensive, safer to use in terms of side effects, and more readily available than their synthetic counterparts" 2 .
This combination of accessibility and potential efficacy makes plants like Lannea kerstingii particularly attractive candidates for further development.
The story of Lannea kerstingii exemplifies how traditional knowledge and modern science can converge to address contemporary challenges. What was once a traditional remedy is now revealing its secrets through the tools of modern laboratory science, offering potential solutions to the urgent crisis of antimicrobial resistance.
As research continues, plants like Lannea kerstingii remind us that nature holds immense chemical diversity, much of which remains unexplored. In our race against evolving pathogens, preserving both biological diversity and traditional knowledge may prove as important as maintaining high-tech laboratories. The leaves of this unassuming tree represent not just potential future medicines, but also hope that solutions to some of our most pressing health challenges may be growing all around us, waiting for science to recognize their value.