Madecassic Acid from Gotu Kola Shows Promise as a Novel Antibiotic by Targeting Bacterial Cytochrome bd

Table of Contents

1. Key Highlights
2. Introduction
3. From skincare staple to antibiotic candidate
4. How madecassic acid disables a bacterial respiratory engine
5. From extract to derivatives: how the team validated activity
6. Why cytochrome bd is an attractive and underexploited antibiotic target
7. Chemical tractability: why madecassic acid can be optimized
8. Real-world hurdles: permeability, resistance and pharmacology
9. Skincare implications: what the discovery means for products containing Centella extracts
10. The development pathway: from laboratory discovery to clinical candidate
11. Strategies to limit resistance and maximize utility
12. Conservation, supply and sustainability considerations
13. How this discovery fits into the broader antimicrobial landscape
14. Next research priorities and experimental milestones
15. What this means for clinicians, formulators and policymakers
16. Voices from the research
17. Practical scenarios where a cytochrome bd inhibitor could matter
18. Balancing therapeutic promise with realistic timelines
19. Ethical and social considerations
20. FAQ

Key Highlights

• Researchers at the University of Kent and UCL have identified madecassic acid, a compound from Centella asiatica, as an inhibitor of cytochrome bd, a bacterial respiratory complex essential to many pathogens but absent in humans.
• Laboratory and computational work showed madecassic acid and three synthetically modified variants block cytochrome bd, halt growth of antibiotic‑resistant E. coli, and — at higher concentrations for one variant — kill the bacteria outright.
• The discovery points to a new antibiotic scaffold with a chemistry amenable to optimization, while raising questions for skincare use of Centella-derived products and outlining a multi-step path toward therapeutic development.

Introduction

Centella asiatica, widely known as gotu kola, is a mainstay of traditional medicine and a celebrated ingredient across Korean skincare lines for its anti‑inflammatory and soothing properties. Now a molecule isolated from that plant, madecassic acid, has surfaced as a candidate for a very different role: disabling a bacterial respiratory complex critical for survival during infection.

A collaboration between microbiologists at the University of Kent and chemists at University College London combined large-scale computational screening with bench-top experiments to show that madecassic acid binds tightly to cytochrome bd, a bacterial oxidase not found in humans or animals. When this complex is blocked, resistant Escherichia coli strains stop growing and—depending on the variant—can be killed. The work, published in RSC Medicinal Chemistry, outlines a clear mechanism and establishes a starting point for medicinal chemistry campaigns that could yield new antibiotics.

The timing is striking. Public-health forecasts place antimicrobial resistance among the greatest threats to global mortality this century, and a steady pipeline of new drug classes has not kept pace. Identifying natural molecules with selective modes of action against bacterial targets is one effective route to replenishing that pipeline. Madecassic acid’s selectivity for a bacterial-only respiratory enzyme and its chemical tractability position it as a lead scaffold worth advancing. The path to a licensed antibiotic will be long, but the findings provide both mechanistic clarity and practical routes for optimization.

From skincare staple to antibiotic candidate

Centella asiatica has a long history in folk medicine across Asia, where it has been used to treat wounds, inflammation and a variety of skin complaints. Modern skincare formulations capitalize on several active constituents extracted from the plant—among them madecassoside, asiatic acid and madecassic acid—promoting barrier repair and reduced redness.

Cosmetic use has produced a high public familiarity with the herb, but the new research shifts attention from topical benefits to an antimicrobial mechanism that operates at the molecular level inside bacterial cells. The team isolated madecassic acid from Vietnamese plant material and then used computational docking and biochemical assays to demonstrate how the molecule interacts with bacterial proteins. That transition—from a consumer product ingredient to a potential therapeutic scaffold—underscores the scientific value of revisiting traditional remedies with modern tools.

This is not the first time a natural product used in traditional medicine has yielded a modern drug. Penicillin and other antibiotics originated from microorganisms; plant-derived compounds such as berberine and others have been investigated for antimicrobial activity. What distinguishes madecassic acid is its apparent specificity for cytochrome bd, a protein complex with a limited phylogenetic distribution that includes many pathogenic bacteria but excludes human mitochondria. A bacterial-specific target reduces the risk of host toxicity and simplifies selectivity requirements for drug candidates.

How madecassic acid disables a bacterial respiratory engine

Bacteria depend on energy generation systems closely tied to survival and virulence. In many pathogens, cytochrome bd oxidases play a crucial role when oxygen levels are low or during the stress of infection. These enzymes help maintain respiration and redox balance under conditions that inhibit other terminal oxidases.

The investigators used computational screening to predict a strong binding interaction between madecassic acid and the cytochrome bd complex. Subsequent lab experiments confirmed that madecassic acid inhibits cytochrome bd activity and impairs growth of antibiotic‑resistant E. coli strains. The binding appears to block the enzyme’s function rather than simply destabilizing the protein, which explains the bacteriostatic effect observed at modest concentrations and bactericidal action by one variant at higher concentrations.

Targeting a terminal oxidase has strategic advantages. Because cytochrome bd is not present in humans, inhibitors can theoretically achieve a wide therapeutic window. In addition, cytochrome bd contributes to bacterial survival in oxygen‑limited niches such as abscesses, the urinary tract, or intracellular host environments, suggesting inhibitors could be active where some existing antibiotics struggle.

The study focused on E. coli as a model Gram-negative pathogen. That choice was informative: Gram-negative bacteria present additional barriers for drug entry—an outer membrane and efflux pumps—that any clinical candidate must overcome. The fact that madecassic acid and its variants can inhibit E. coli growth indicates these compounds either penetrate these defenses to a useful extent or act under conditions that make cytochrome bd especially vulnerable.

From extract to derivatives: how the team validated activity

The research combined in silico methods, classical natural‑product isolation and medicinal chemistry:

• Computational screening narrowed candidate interactions between plant compounds and bacterial proteins. Docking experiments suggested madecassic acid fit well into a functional pocket of cytochrome bd.
• Researchers isolated madecassic acid from Centella asiática harvested in Vietnam, providing a natural source of the molecule for experimental work. Isolation from plant material remains a practical first step for validating biological activity.
• Chemists synthesized three modified derivatives of madecassic acid to probe structure–activity relationships. These modifications preserved the core scaffold while altering peripheral functionalities to test binding strength and biological effects.
• Biochemical assays measured cytochrome bd activity in the presence of the parent compound and derivatives. All variants inhibited the enzyme; one variant also caused bacterial killing at higher concentrations in culture.
• Microbial growth assays quantified the impact on antibiotic‑resistant E. coli strains. The compounds reduced growth and, for the most active derivative, led to bactericidal outcomes under specific conditions.

This workflow—natural-product discovery through computational prioritization followed by targeted modification and validation—illustrates a productive path for converting botanical chemistry into drug leads. Importantly, moving from a natural extract to synthetically tuned variants allows chemists to improve potency, solubility and pharmacokinetic traits that raw plant molecules often lack.

Why cytochrome bd is an attractive and underexploited antibiotic target

Cytochrome bd oxidases are widespread in bacteria but absent in mammalian mitochondria, which use cytochrome c oxidase as their terminal oxidase. That difference creates an opportunity for selective toxicity—a fundamental requirement for antimicrobial drugs.

Several features make cytochrome bd particularly promising:

• Functional importance during infection: Many pathogens upregulate cytochrome bd in response to host-imposed stresses such as low oxygen, nitric oxide or reactive oxygen species. Inhibiting bd can cripple bacterial survival precisely when the host environment otherwise limits bacterial fitness.
• Limited host off-target risk: Because humans lack cytochrome bd, inhibitors are less likely to hit conserved mammalian respiratory complexes.
• Complementarity to existing antibiotics: Drugs that impair bacterial energy metabolism can potentiate antibiotics that act on cell-wall synthesis, DNA replication, or protein synthesis, offering a route to combination therapies that slow resistance.
• Narrow species distribution and conservation pattern: Cytochrome bd is conserved across many pathogenic species, including Gram-negative Enterobacterales and some Gram‑positive organisms, offering the potential for a broad-spectrum class that nonetheless avoids mammalian targets.

Historically, cytochrome bd has received less attention than targets such as ribosomes, cell-wall enzymes or DNA gyrase. That relative neglect creates both an opportunity and a challenge. Opportunity, because fewer existing resistance mechanisms target bd; challenge, because less is known about inhibitor design and the physiological roles of bd across different pathogens and infection settings.

Chemical tractability: why madecassic acid can be optimized

Natural products frequently serve as starting points for drug development, but not all natural scaffolds lend themselves to optimization. Madecassic acid has two practical advantages:

• Clear synthetic handles: Its chemical structure contains functional groups that chemists can modify without destroying the core scaffold, enabling systematic exploration of substitutions that affect potency and pharmacokinetics.
• Demonstrated structure‑activity relationship: The Kent–UCL team produced three variants with retained or improved activity. Even modest increases in potency at this stage validate the scaffold and justify further medicinal chemistry.

Optimization priorities for madecassic acid derivatives will include enhancing potency against target bacteria, improving permeability across Gram‑negative outer membranes, reducing susceptibility to bacterial efflux pumps, increasing metabolic stability and achieving favorable absorption, distribution, metabolism and excretion (ADME) properties.

Several classic medicinal‑chemistry strategies will apply: altering lipophilicity to improve membrane passage, introducing polar surface elements to balance solubility, and installing metabolic blockers to avoid rapid clearance. Parallel assays to evaluate mammalian cell toxicity will be essential to ensure selectivity is retained as modifications proceed.

Real-world hurdles: permeability, resistance and pharmacology

Identifying a molecular interaction is only the start. Transitioning a plant-derived inhibitor to a systemic antibiotic faces several predictable technical challenges:

• Membrane permeability and efflux: Gram‑negative bacteria possess an outer membrane and active efflux systems that reduce intracellular concentrations of many compounds. Effective inhibition of E. coli growth suggests madecassic acid can reach its target to some extent, but medicinal chemistry must further improve uptake and limit efflux.
• Pharmacokinetics and bioavailability: Many natural compounds have poor solubility or are rapidly metabolized, complicating systemic administration. Oral bioavailability, tissue penetration into infection sites and half-life in circulation will be key variables to optimize.
• Toxicity and selectivity: Preclinical toxicology must exclude off‑target effects. Even with a bacterial‑specific target, other liabilities—such as hormonal, hepatic or immunological interference—can arise from scaffold modifications.
• Resistance emergence: Bacteria can evolve resistance through target mutations, overexpression of alternative respiratory enzymes, or enhanced efflux. Early evaluation of resistance frequency and mechanisms helps design molecules and treatment regimens that minimize rapid resistance development.
• Spectrum of activity: Cytochrome bd is present in many but not all pathogens. Determining which clinical indications—urinary tract infections, respiratory infections, soft tissue abscesses, intracellular infections—are most amenable to a bd inhibitor will guide development priorities.

Addressing these hurdles requires an iterative program of chemistry, microbiology and pharmacology. The early success with madecassic acid provides a scaffold for iterative improvement, but it does not guarantee that a drug candidate will emerge without sustained investment and careful target product profile (TPP) definition.

Skincare implications: what the discovery means for products containing Centella extracts

Centella-derived ingredients, including madecassoside and madecassic acid derivatives, appear in an array of cosmetic products marketed for sensitive, acne-prone or barrier‑impaired skin. The new findings prompt two practical questions: do typical formulations contain madecassic acid at concentrations that affect skin bacteria, and should formulators reassess claims in light of potential antimicrobial effects?

Current evidence suggests standard concentrations used for soothing or anti‑inflammatory effects are low. Skincare formulations prioritize safety and broad tolerability; they typically do not deliver pharmacological doses sufficient to sterilize skin or eliminate significant portions of the microbiome. Nevertheless, three points merit attention:

• Subtle microbiome shifts: Even low-level antimicrobial activity can alter the relative abundance of skin commensals over time, with unknown effects on skin health. Studies focusing on chronic, low-dose exposure to Centella extracts would clarify this risk.
• Product claims and regulation: If formulators begin to market Centella-containing products for antimicrobial or wound‑healing purposes, different regulatory pathways and evidence requirements apply in many jurisdictions. Translating a botanical component into a dermatological drug would require clinical data and explicit safety testing.
• Opportunity for topical therapeutics: The cytochrome bd mechanism offers a potential avenue for topical antiseptics or prescription dermatologic agents. For localized skin infections, a topical agent that selectively targets bacterial respiration with minimal host toxicity could be attractive, provided formulations deliver sufficient local concentrations.

For consumers, the immediate implication is modest: continued use of Centella-containing cosmetics remains safe within established regulatory frameworks. For industry and clinical researchers, the discovery opens a conversation about intentional formulation strategies and controlled trials to characterize microbiome effects.

The development pathway: from laboratory discovery to clinical candidate

Advancing madecassic acid derivatives from an academic discovery to a licensed antibiotic follows a multi-stage process:

1. Lead optimization
   • Iterative medicinal chemistry to improve potency, target engagement, ADME properties and safety.
   • Parallel in vitro assays to test efficacy across pathogen panels, including multidrug‑resistant strains, and to measure synergy with existing antibiotics.
2. Preclinical validation
   • In vivo efficacy models (e.g., murine infection models) to demonstrate treatment effect at achievable doses.
   • Pharmacokinetic and pharmacodynamic (PK/PD) studies to define dose–exposure–response relationships.
   • Toxicology studies across organ systems to establish a safe starting dose for human trials.
3. Early clinical trials
   • Phase 1 human studies focusing on safety, tolerability and PK in healthy volunteers.
   • Phase 2 trials to demonstrate efficacy in defined infection types and refine dosing.
   • Phase 3 pivotal trials comparing the candidate to standard of care.
4. Regulatory review and post‑approval surveillance
   • Submission of dossiers demonstrating safety and efficacy.
   • Post-approval monitoring for resistance, adverse events and real-world effectiveness.

Antibiotic development often takes a decade or more and requires tens to hundreds of millions of dollars. Public-private partnerships, philanthropic funding and regulatory incentives (such as priority review vouchers or accelerated approval pathways for unmet medical needs) can accelerate progress. Because madecassic acid is a natural product, scalable synthesis or semi-synthetic production will also be crucial to ensure supply without compromising biodiversity or quality.

Strategies to limit resistance and maximize utility

Anticipating resistance is part of modern antibiotic design. Several strategies can extend the clinical utility of a cytochrome bd inhibitor:

• Combination therapy: Pairing a bd inhibitor with an antibiotic that stresses bacterial cell-wall integrity, protein synthesis or DNA replication can produce synergistic effects and reduce the likelihood that a single mutation will nullify treatment.
• Targeting multiple respiratory pathways: Dual inhibitors that affect cytochrome bd plus other elements of bacterial energy metabolism would make simultaneous resistance mutations less likely.
• Restrictive stewardship: Reserve use for defined high-risk infections where bd inhibition adds clear advantage, rather than broad empirical use.
• Diagnostic coupling: Rapid diagnostics that identify infections in which cytochrome bd is essential or highly expressed could direct therapy to patients most likely to benefit.

These strategies require early planning. Evaluating potential cross-resistance with existing antimicrobials and quantifying the ease with which bd mutations arise in laboratory selection experiments should occur during preclinical work.

Conservation, supply and sustainability considerations

The madecassic acid used in the Kent–UCL study was isolated from Centella material sourced in Vietnam. Natural‑product drug discovery must balance the benefits of biodiversity with the risks of overharvesting and ecological harm. Three practical considerations apply:

• Sustainable sourcing: Partnerships with local growers and adherence to sustainable harvesting practices can ensure ecological stability and equitable benefits to source communities.
• Synthetic chemistry alternatives: Developing efficient synthetic or semi‑synthetic routes reduces pressure on wild plant populations and enables batch‑to‑batch consistency for pharmaceutical production.
• Traceability and regulatory compliance: Compliance with international agreements on access and benefit sharing (such as the Nagoya Protocol) protects source country rights and supports ethical research.

Successful drug development programs often move rapidly from extraction to full synthetic routes once a clinical candidate emerges, ensuring supply security and minimizing environmental impact.

How this discovery fits into the broader antimicrobial landscape

Antimicrobial resistance is a complex, multifactorial global problem. New antibiotics targeting novel bacterial functions are essential components of a broader response that also includes stewardship, diagnostics, sanitation and vaccination.

Madecassic acid represents a lead molecule that brings two attributes the field needs: a novel, selective target and a scaffold amenable to chemical refinement. While the road to a marketable antibiotic is long, such discoveries replenish the discovery pipeline and diversify mechanistic approaches.

Examples of other innovative strategies in recent years include agents that restore activity of existing antibiotics (beta‑lactamase inhibitors), compounds that disarm virulence rather than kill bacteria directly, and molecules that inhibit bacterial communication (quorum sensing). A cytochrome bd inhibitor could complement these approaches, especially where bacterial energy homeostasis underlies persistence or tolerance to other drugs.

Next research priorities and experimental milestones

To translate the current findings into therapeutic prospects, researchers should prioritize the following actions:

• Expand pathogen panel testing: Determine the activity spectrum across clinically relevant Gram‑negative and Gram‑positive species, including multidrug‑resistant clinical isolates.
• Determine in vivo efficacy: Employ animal infection models to assess whether enzyme inhibition translates to therapeutic benefit in tissue‑relevant contexts.
• Characterize resistance mechanisms: Use serial passage and targeted mutagenesis to reveal likely resistance pathways and design around them.
• Optimize physicochemical properties: Pursue medicinal chemistry to improve solubility, metabolic stability and membrane permeability while retaining selectivity.
• Assess safety and off‑target effects: Conduct mammalian cell assays, tissue toxicity studies and early in vivo toxicology to evaluate safety margins.
• Investigate combinatorial regimens: Test combinations with existing antibiotics to identify synergistic pairs that reduce necessary dosages and delay resistance.

Funding agencies, pharmaceutical partners and interdisciplinary consortia will likely be necessary to sustain the development pipeline from academic discovery through preclinical and clinical stages.

What this means for clinicians, formulators and policymakers

Clinicians should view the finding as a promising early-stage discovery rather than a ready therapeutic option. For formulators and manufacturers of topical products containing Centella extracts, the work suggests renewed attention to ingredient characterization and potential microbiome effects, particularly for products intended for medicated or healing claims.

Policymakers and funders should recognize the discovery as an example of how investing in natural‑product chemistry and academic–industry collaborations yields new leads against antimicrobial resistance. Programs that support translational work—from hit validation to lead optimization—can accelerate the conversion of scientific insights into clinical tools.

Voices from the research

Lead author Dr. Mark Shepherd, Reader in Microbial Biochemistry at the University of Kent, framed the discovery within a long tradition: "Plants have been a source of natural medicines for millennia, and now contemporary research approaches can reveal the mechanisms of action. This is an exciting time, and we hope to further our understanding of natural antimicrobials from plants, nature's great chemical factories."

That sentiment captures the methodological convergence at work: computational prediction, classical isolation and modern medicinal chemistry. The combination accelerates hypothesis testing and reduces wasted effort on compounds lacking a clear mechanism.

Practical scenarios where a cytochrome bd inhibitor could matter

Understanding when a bd inhibitor would be clinically useful requires attention to infection biology. Potential scenarios include:

• Urinary tract infections (UTIs): E. coli is the dominant causative agent. A bd inhibitor that can reach urinary concentrations sufficient to block respiration would be useful, particularly for drug‑resistant strains.
• Intracellular infections: Pathogens that find refuge within host cells or in low‑oxygen microenvironments rely on alternative respiratory pathways, making bd inhibition strategically effective.
• Biofilm-associated infections: Bacteria in biofilms often experience oxygen limitation and metabolic heterogeneity. Agents that target respiration could impair biofilm resilience and increase susceptibility to other drugs.
• Topical and wound infections: For localized infections of the skin or soft tissue, topical formulations delivering higher local concentrations of a bd inhibitor may have fewer systemic toxicity constraints.

The specific clinical niches will depend on the final molecule’s pharmacological profile, safety data and route of administration.

Balancing therapeutic promise with realistic timelines

Breakthroughs in target identification are necessary but not sufficient for new treatments. Historically, bringing a new antibiotic to market takes a sustained effort spanning discovery, optimization, animal models, regulatory toxicology and multiple phases of human trials. Costs and timeframes vary, but planning for a multi‑year, resource‑intensive development program is essential.

The advantage of a scaffold with existing medicinal‑chemistry tractability is that optimizations can proceed faster than with intractable natural products. Nevertheless, stakeholders should temper expectations with an understanding of regulatory demands and the need for robust safety data, especially for systemic agents.

Ethical and social considerations

Drug development decisions carry ethical dimensions. Prioritizing global access, affordable pricing and stewardship policies will be important if a madecassic-based antibiotic reaches the market. Ensuring equitable benefit sharing with plant source communities and avoiding exploitative sourcing practices are also ethical imperatives tied to natural‑product research.

Finally, public communication should be measured: consumers should not assume that cosmetic concentrations of Centella confer antimicrobial protection against resistant infections, and practitioners should avoid off-label use of unapproved formulations.

FAQ

Q: What is madecassic acid and where does it come from? A: Madecassic acid is a triterpenoid compound found in Centella asiatica (gotu kola). The plant has been used traditionally for skin healing and is a common ingredient in topical cosmetics. Researchers isolated madecassic acid from plant material and validated its activity against a bacterial respiratory enzyme.

Q: How does madecassic acid act against bacteria? A: The compound binds to and inhibits cytochrome bd, a terminal oxidase used by many bacteria during respiration, particularly under low‑oxygen or stress conditions. Blocking this enzyme impairs bacterial energy metabolism and, in laboratory tests, halted growth of antibiotic‑resistant E. coli. One modified derivative achieved bactericidal activity at higher concentrations.

Q: Is cytochrome bd present in humans? A: No. Humans and other animals use different respiratory complexes in mitochondria, and cytochrome bd is a bacterial‑specific enzyme. That difference makes bd an attractive selectivity target for antibiotics, potentially reducing host toxicity.

Q: Does this mean Centella-containing skincare products are antibacterial? A: Not necessarily. Cosmetic formulations typically contain low concentrations of active plant extracts aimed at soothing or repairing skin, not delivering pharmacological doses that would kill bacteria. The discovery suggests the possibility of antimicrobial activity under certain conditions, but product concentrations, vehicle formulation and exposure time all determine activity. More research is needed to assess long‑term microbiome effects from regular cosmetic use.

Q: Could madecassic acid become a new antibiotic soon? A: The discovery marks an early-stage lead. Advancing to a clinical antibiotic requires extensive medicinal chemistry, preclinical studies, toxicology, and phased human trials. That process often takes many years and substantial investment. The current results justify further development but do not imply immediate clinical availability.

Q: What challenges must be overcome to develop madecassic-derived drugs? A: Key challenges include improving potency and selectivity, ensuring membrane permeability especially for Gram‑negative pathogens, avoiding rapid metabolic clearance, minimizing host toxicity, and limiting the development of bacterial resistance. Supply chain and sustainability considerations for plant-derived starting material also require resolution through synthetic routes or responsible sourcing.

Q: Are there advantages to targeting cytochrome bd rather than conventional antibiotic targets? A: Targeting cytochrome bd offers selectivity because the enzyme is absent in humans, and it plays a central role when bacteria face host-imposed stresses. Inhibiting bd could be particularly effective in low‑oxygen infection niches and could be used in combination therapies to enhance efficacy and reduce resistance emergence.

Q: What further experiments will researchers perform? A: Next steps include expanding testing across diverse pathogens and resistant strains, characterizing resistance mechanisms, optimizing chemical derivatives for potency and pharmacokinetic properties, evaluating in vivo efficacy in infection models, and conducting preclinical safety studies.

Q: How should policymakers and funders respond to this discovery? A: Funding translational research, including medicinal chemistry programs and preclinical validation, would accelerate progress. Policies that encourage public–private partnerships, incentivize antibiotic development and ensure equitable access to resulting therapies would increase the likelihood that promising laboratory leads translate into clinical tools.

Q: What does this mean for global antimicrobial resistance efforts? A: The discovery adds a new mechanistic approach to a limited arsenal of antibiotic options. While no single discovery solves the broader AMR crisis, diversifying targets and scaffolds strengthens long‑term resilience against resistant pathogens and provides options for difficult-to-treat infections.