Its bright red color and refreshing sour taste have long made it a popular ingredient in herbal beverages. But behind the cup of roselle tea commonly served at family tables lies a much more serious potential: the ability to inhibit bacteria that cause skin infections, typhoid fever, and even hospital-acquired infections that often threaten patients with compromised immunity.
Research published in the journal Sainstech revealed a finding worth noting. Ethanol extract of roselle flowers (Hibiscus sabdariffa L.) was shown to inhibit the growth of three pathogenic bacteria: Staphylococcus aureus, Staphylococcus epidermidis, and Salmonella typhi. Interestingly, its inhibitory activity was not uniform. Roselle was considerably more effective against Gram-positive bacteria than Gram-negative bacteria.
From a Farm in Depok to a Laboratory in Bogor
The research began on a modest farm in Simpangan, Depok. Fresh roselle flowers that were still in the budding stage, approximately three to four weeks old, were harvested from local farmers. From there, a lengthy process began: sorting, air-drying for three weeks, grinding into powder, and extraction using the maceration method with 70% ethanol.
Testing was conducted at the Bacteriology Laboratory of the Research Center for Veterinary Science (BBALITVET), Cimanggu, Bogor. The research team employed two standard methods: the disk diffusion method to measure the inhibition zone and the dilution method to determine the Minimum Inhibitory Concentration (MIC), namely the lowest concentration that can still inhibit bacterial growth.
Before being tested against bacteria, the roselle powder and extract were first analyzed for their chemical constituents. The results were consistent: flavonoids, saponins, tannins, phenolics, triterpenoids, and glycosides were all detected. These six compounds are known to possess antibacterial activity and are therefore suspected to be the “troops” responsible for roselle's inhibitory effects.
The Numbers Speak
At an extract concentration of 50%, the inhibition zones were quite impressive. S. aureus recorded the largest diameter of the growth inhibition zone, averaging 28 mm, with an MIC of 5%. S. epidermidis followed with an inhibition zone of 26.6 mm and an MIC of 4%. Meanwhile, Salmonella typhi, the Gram-negative bacterium that causes typhoid fever, produced an inhibition zone of only 18 mm, with an MIC of 7%.
The difference in responses between Gram-positive and Gram-negative bacteria is not coincidental. Gram-negative bacteria possess an additional outer membrane that serves as a protective layer, making it more difficult for active compounds in roselle extract to penetrate their cell walls. In contrast, Gram-positive bacteria, which have only a peptidoglycan layer, are more susceptible to phenolic and flavonoid compounds.
The clinical relevance of these findings is considerable. S. epidermidis, for example, is known to cause nosocomial infections and form biofilms on medical equipment. This bacterium can infect patients with compromised immunity, including people with AIDS, newborn infants, and long-term hospitalized patients. S. aureus, on the other hand, is responsible for conditions ranging from boils and acne to septic arthritis.
Potential Waiting to Be Developed
Dr. drg. Andi Triawan, Sp.Ort., from the Department of Orthodontics, Faculty of Dentistry, Universitas Gadjah Mada, views these findings within a broader context. In a discussion on the potential of natural materials for oral health, he noted that bacteria such as S. aureus and S. epidermidis are also relevant in the context of oral infections and orthodontic appliances.
“Research such as this opens the door to further exploration. Natural materials shown to have antibacterial activity in vitro need to be investigated further, including their safety in biological tissues and their effectiveness under more complex clinical conditions.”
An important caveat must be emphasized: this study was in vitro, meaning that it was conducted under controlled laboratory conditions. The journey from a Petri dish to clinical application remains a long one and requires a series of further studies.
However, its social context cannot simply be ignored. The increasing cost of conventional antibiotics has led many people to seek alternatives. Roselle grows well in Indonesia's tropical climate, is easy to cultivate, and has long been familiar in Indonesian households. If its antibacterial potential can be developed into a standardized formulation, this plant could become part of a more affordable healthcare solution.
The question is no longer whether roselle has benefits. Laboratory data have already answered that. The question is: how seriously are we prepared to develop its potential.
Authors: Nanda Ayu, drg. Achmad Zam Zam Aghasy, M.Kes.
Photo: Pexels