Diabetic wounds are a serious health concern because they can be difficult to heal and are vulnerable to bacterial infection. Long-term high blood sugar can be associated with impaired circulation, nerve damage, and weakened immune responses. These conditions can allow bacteria to colonize wounds, delay healing, and increase the risk of severe complications, including disability and lower-limb amputation.
Among the bacteria commonly linked to diabetic wounds is S. aureus. This Gram-positive bacterium can produce factors that damage tissue and form biofilms, allowing infections to persist. Another important pathogen is Pseudomonas aeruginosa, a Gram-negative bacterium known for its strong resistance mechanisms, including low membrane permeability, drug-efflux systems, and biofilm formation. The increasing challenge of antimicrobial resistance has encouraged researchers to explore natural products as potential sources of new antibacterial agents.
Traditional Yellow Root Under Scientific Investigation
Fibraurea tinctoria is an indigenous medicinal plant widely distributed in Kalimantan, Indonesia. Communities have traditionally used the plant for conditions involving infection and inflammation. Previous phytochemical research has identified several bioactive compound groups in the plant, including alkaloids, flavonoids, tannins, saponins, triterpenoids, and phenolic compounds. Berberine, an alkaloid found in the plant, has received particular attention for its reported antibacterial properties.
Earlier studies had reported antibacterial activity from F. tinctoria, but much of the available evidence focused on stem extracts or aqueous infusions. Evidence specifically examining ethanol extracts from the roots against both S. aureus and P. aeruginosa remained limited.
Ayuni Syahira and colleagues addressed that gap by testing root extract at five concentrations: 2%, 4%, 6%, 8%, and 10%. Their work also allowed the researchers to compare how a Gram-positive bacterium and a Gram-negative bacterium responded to the same plant extract.
Laboratory Testing in East Kalimantan
The laboratory experiment was conducted at the Bacteriology Laboratory of the Medical Laboratory Technology Department at Poltekkes Kemenkes Kalimantan Timur, Indonesia. Plant identification was performed at the Laboratory of Plant Anatomy and Systematics, Faculty of Mathematics and Natural Sciences, Universitas Mulawarman.
The researchers collected F. tinctoria roots from Central Kalimantan. The roots were washed, dried, ground into powder, and soaked in 96% ethanol to obtain the extract. The concentrated extract was then diluted to produce the five test concentrations.
The antibacterial test used a disk-diffusion method. In simple terms, paper disks containing different extract concentrations were placed on laboratory plates containing the bacteria. After 24 hours of incubation at 37 degrees Celsius, the researchers measured the clear areas surrounding the disks. A larger clear area indicated stronger inhibition of bacterial growth. Ciprofloxacin served as the positive control, while sterile distilled water was used as the negative control.
Stronger Inhibition as Extract Concentration Increased
The clearest antibacterial effect appeared against S. aureus. The 2% extract produced no measurable inhibition zone, but activity emerged at 4% and increased at higher concentrations.
The measured average inhibition zones were:
- 2%: 0.00 ± 0.00 mm
- 4%: 10.00 ± 0.58 mm
- 6%: 11.33 ± 0.47 mm
- 8%: 12.00 ± 1.15 mm
- 10%: 13.67 ± 0.82 mm
The 10% extract therefore produced the largest inhibition zone against S. aureus.
Statistical analysis showed that extract concentration had a significant effect on S. aureus growth inhibition, with p < 0.001. The researchers calculated an eta-squared effect size of 0.97, indicating that extract concentration accounted for approximately 97% of the observed variation in inhibition-zone diameter under the experimental conditions.
However, the difference between the 8% and 10% concentrations was not statistically significant. This suggests that increasing the concentration beyond 8% may provide only limited additional antibacterial activity under the conditions tested. More concentration levels would be needed to determine whether the effect reaches a plateau.
The result was very different for P. aeruginosa. None of the concentrations from 2% through 10% produced a measurable inhibition zone. Because there was no detectable inhibition, the researchers did not perform statistical comparisons for this bacterium.
Why Did the Extract Affect One Bacterium but Not the Other?
The researchers from Poltekkes Kemenkes Kalimantan Timur suggest that the difference may be related to the structural characteristics of the two bacterial groups. Bioactive compounds associated with F. tinctoria, including berberine, flavonoids, tannins, saponins, triterpenoids, and phenolic compounds, may interfere with bacterial membranes, nucleic-acid synthesis, and metabolic processes.
However, the researchers emphasized an important limitation: their experiment did not directly measure the chemical composition of the specific root extract used. The connection between particular compounds and the observed antibacterial effect therefore remains an inference based partly on previous phytochemical studies. Direct quantitative profiling of the extract would be necessary to establish which compounds are responsible.
The absence of measurable activity against P. aeruginosa should also be interpreted cautiously. Its outer membrane and other defense mechanisms can restrict the entry and accumulation of antibacterial compounds. The disk-diffusion method itself may also fail to detect some forms of antibacterial activity that require prolonged contact or different concentrations.
Potential for Natural Antibacterial Development
The findings provide preliminary scientific evidence supporting further investigation of F. tinctoria root extract as a potential natural antibacterial agent, particularly against Gram-positive bacteria such as S. aureus. The results do not, however, establish the extract as a ready-to-use treatment for diabetic wounds.
Ayuni Syahira, I Gede Andika Sukarya, Tiara Dini Harlita, and Askur recommend further testing to determine minimum inhibitory and bactericidal concentrations, quantify the extract's active phytochemicals, assess activity against multidrug-resistant clinical isolates, and examine biofilm inhibition and toxicity. Studies using diabetic wound models are also needed before any potential application in humans can be considered.
The researchers' interpretation is therefore best understood as an early-stage finding. As the authors from Poltekkes Kemenkes Kalimantan Timur demonstrate, the ethanol root extract showed a concentration-dependent inhibitory effect against S. aureus, reaching its strongest measured effect at 10%. At the same time, the extract showed no detectable inhibition of P. aeruginosa under the tested conditions.
Author Profile
Ayuni Syahira, I Gede Andika Sukarya, Tiara Dini Harlita, and Askur are affiliated with Poltekkes Kemenkes Kalimantan Timur. I Gede Andika Sukarya is identified as the corresponding author. The published article does not provide the academic degrees or individual fields of expertise of the four authors, so those details cannot be stated reliably from the source.
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