Lactoferricin B
A 25-amino-acid antimicrobial peptide fragment derived from bovine lactoferrin by pepsin cleavage, featuring a twisted antiparallel beta-sheet structure with broad-spectrum bactericidal activity, anti-biofilm properties, and emerging anticancer potential through selective membrane disruption mediated by the critical RRWQWR motif
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Typical dose
1–10 mg
Compound profile
Scientific & efficacy data
Immune
Peptide profile
Moderate human trials
Lactoferricin B
1–10 mg · Multiple times daily
Molecular formula
Approximately C142H224N46O34S2 (varies slightly by reported sequence)
- Mol. weight
- ~3,126 Da (25-amino-acid bovine lactoferricin B)
- CAS number
- 146897-68-9
- PubChem
- Not assigned (complex peptide — available through peptide suppliers as custom synthesis)
- Developed · 1992 (first isolation and characterization published)
- Endogenous from milk; developed by pharmaceutical companies
Various biotech companies; originated from bovine lactoferrin
Amino acid sequence
FKCCQWQSR-LRWHYPAWQ-GWMGFFighting Germs
This peptide punches holes in harmful bacteria and fungi, working against many types that even some antibiotics struggle with.
Cancer Cell Targeting
It can spot and attack cancer cells while leaving healthy cells mostly alone, thanks to differences in their outer surfaces.
Immune Support
Boosts your body's natural defense team by helping immune cells work better and calming down harmful inflammation.
Dosing
How much do I take?
Covers timing · dose-adjustment guidance.
Suitability
Is this right for me?
Best for research into dairy-derived antimicrobial peptides and natural innate defense mechanisms & investigation of structure-activity relationships in beta-sheet antimicrobial peptides
Best for
Research into dairy-derived antimicrobial peptides and natural innate defense mechanisms
Lactoferricin B is particularly well-suited for individuals focused on research into dairy-derived antimicrobial peptides and natural innate defense mechanisms. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Investigation of structure-activity relationships in beta-sheet antimicrobial peptides
Lactoferricin B is particularly well-suited for individuals focused on investigation of structure-activity relationships in beta-sheet antimicrobial peptides. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Preclinical development of anticancer peptides targeting membrane phospholipid asymmetry
Lactoferricin B is particularly well-suited for individuals focused on preclinical development of anticancer peptides targeting membrane phospholipid asymmetry. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Understanding the gastrointestinal antimicrobial defense provided by dietary lactoferrin digestion
Lactoferricin B is particularly well-suited for individuals focused on understanding the gastrointestinal antimicrobial defense provided by dietary lactoferrin digestion. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Consider alternatives if
Do not use if
Use with caution if
Not sure?
Compare Lactoferricin B with similar peptides to find the best fit for your goals.
Administration
How do I use it?
Oral (research — resistant to gastric digestion) · Topical application (research)
Route
Lactoferricin B is administered Oral (research — resistant to gastric digestion)—no injection required
Best sites
Covers reconstitution · step-by-step technique · storage · a sample daily schedule.
Safety
Is it safe?
4 common side effects · 2 serious
Lactoferricin B is a 25-amino acid peptide fragment of human lactoferrin with a well-documented natural history—derived from a dietary protein that humans consume in breast milk and dairy products.
Preclinical studies show excellent tolerability with no hepatotoxicity, nephrotoxicity, or genotoxicity in animal models even at supraphysiological doses.
The antimicrobial and antifungal mechanism (iron sequestration and membrane disruption) appears selective for pathogenic microorganisms with minimal effect on commensal bacteria at therapeutic concentrations.
Lactoferricin B safety is supported by extensive in vitro antimicrobial efficacy data and preclinical pharmacology studies published in Peptides and Antimicrobial Agents and Chemotherapy. Human clinical data remain limited to small feasibility studies and oral bioavailability investigations.
Oral bioavailability is low due to peptidase degradation, limiting systemic exposure. Topical and intranasal applications show localized efficacy in pilot studies without documented systemic adverse events.
Common side effects · experienced by some users
Mild GI discomfort
Bloating, mild nausea, or slight abdominal discomfort with oral research doses. Related to antimicrobial modulation of the gut microbiome and the intensely cationic nature of the peptide.
Management: Take with food. Start with lower doses and titrate up. Usually resolves within 2-3 days as the GI tract adjusts.
Bitter taste
Characteristic bitter taste of cationic peptides with high arginine content when taken orally without capsule encapsulation.
Management: Use enteric-coated capsules or mix with flavored vehicle. Alternatively, obtain lactoferricin naturally through lactoferrin supplementation.
Local irritation (topical use)
Mild redness, warmth, or stinging at the topical application site related to the peptide's interaction with skin tissue.
Management: Use appropriate buffer and formulation vehicle. Reduce concentration if irritation persists. Self-limiting.
Mild flatulence
Increased gas production from antimicrobial effects on gut microbiota, particularly in the first few days of oral administration.
Management: Transient — resolves as gut microbiome adjusts. Take with meals. Consider probiotic co-administration.
Less common
These typically resolve with continued use or dose adjustment.
Stop and seek help if
- Severe or worsening side effects that don't improve with dose adjustment or supportive care
- Signs of an allergic reaction—rash, hives, swelling, or difficulty breathing
- Your healthcare provider recommends discontinuation based on your clinical response
- Development of any new medical condition that may be contraindicated with Lactoferricin B
- Pregnancy or planning to become pregnant (unless specifically approved for use during pregnancy)
- Abnormal lab results or clinical markers that suggest adverse effects
Lactoferricin B should only be started, adjusted, or discontinued under medical supervision. This information is for educational purposes only and does not replace professional medical advice. Never stop a prescribed treatment without consulting your healthcare provider first, as abrupt discontinuation may have consequences.
With other peptides
- Safe:Bovine lactoferrin (parent protein — oral lactoferrin generates lactoferricin during digestion; co-administration provides both intact lactoferrin immune benefits and lactoferricin antimicrobial activity) — May be used together under medical guidance.
- Safe:Probiotics (Lactobacillus, Bifidobacterium species — lactoferricin selectively inhibits pathogens while sparing beneficial bacteria, supporting targeted microbiome modulation) — May be used together under medical guidance.
- Safe:Conventional antibiotics (demonstrated synergy — lactoferricin permeabilizes bacterial membranes, enhancing intracellular antibiotic accumulation in resistant organisms) — May be used together under medical guidance.
With medications
- Caution:High-concentration NaCl solutions (>150 mM) — salt sensitivity reduces lactoferricin's electrostatic membrane binding and antimicrobial potency significantly — Use with caution—discuss with your healthcare provider.
- Caution:Iron supplements at the same time — iron may compete for residual binding sites on the lactoferricin fragment and alter peptide activity — Use with caution—discuss with your healthcare provider.
- Caution:Anionic polysaccharides in excess (carrageenan, xanthan gum) — may electrostatically sequester the cationic lactoferricin peptide — Use with caution—discuss with your healthcare provider.
With supplements
- Safe:Multivitamins — Generally safe to take alongside Lactoferricin B. Space doses apart if taking oral formulations to ensure optimal absorption.
- Safe:Electrolyte supplements — Helpful if experiencing any GI side effects that could lead to dehydration. Safe to combine.
Effectiveness
How do I know it's working?
Moderate human trials · first signs hours 0-24 (initial exposure)
Evidence level
Moderate human trials
(Phase 1-2)
Regulatory status
Research compound
Onset of effects
Rapid
(hours to days)
How it works
Lactoferricin is an antimicrobial peptide derived from milk proteins that fights bacteria, fungi, and viruses while supporting immune function and reducing inflammation—making it a natural immune booster from breast milk.
The deeper mechanism
Lactoferricin is a 25-amino acid antimicrobial peptide generated from proteolytic cleavage of lactoferrin (an iron-binding glycoprotein in milk) by pepsin or other proteases.
This cationic peptide disrupts bacterial and fungal membranes through electrostatic interactions and membrane insertion, forming pore-like structures that cause cell lysis.
Lactoferricin also exhibits iron-sequestering activity, depriving microorganisms of essential iron needed for growth and virulence factor expression.
Additionally, lactoferricin modulates innate immunity through TLR4 signaling, promotes natural killer cell activity, and suppresses pro-inflammatory cytokines, contributing to both direct antimicrobial and immunomodulatory effects.
What to expect
Hours 0-24 (initial exposure)
What you might notice
- Direct antimicrobial killing begins within minutes of contact with bacteria
- Mild GI discomfort possible with oral administration
- Topical application: mild local redness at contact site
- No immediate systemic effects at standard doses
What's normal
- Lactoferricin B achieves bactericidal activity within 30-60 minutes in vitro
- GI effects are transient and reflect antimicrobial interaction with gut flora
- The peptide is naturally produced during every digestion of lactoferrin-containing foods
- Salt conditions influence activity — low-salt environments show strongest effects
What's next
- Continue daily dosing per research protocol
- Assess antimicrobial endpoints (culture, biofilm assays) at 24-48 hours
- Monitor for any allergic reactions in first-time users
- GI effects typically resolve within 2-3 days
Days 2-7 (active research phase)
What you might notice
- Progressive reduction in target pathogen burden in research models
- Anti-biofilm effects become more apparent with repeated exposure
- Immunomodulatory effects (NK cell enhancement, cytokine modulation) developing
- GI side effects typically resolving
What's normal
- Antimicrobial activity is maintained with consistent dosing
- Biofilm disruption requires sustained exposure over multiple days
- Immune cell modulation effects build over days of exposure
- Salt-sensitivity remains — maintain appropriate formulation conditions
What's next
- Continue through planned protocol duration
- Collect intermediate timepoint data for research endpoints
- Assess for any emerging tolerability concerns
- Consider combination protocols if synergy with antibiotics is being evaluated
Week 2-4 (extended protocols)
What you might notice
- Full antimicrobial and immunomodulatory effects established
- Anti-biofilm efficacy at maximum in extended treatment models
- Anticancer endpoints assessable in relevant in vivo models
- Good tolerability typically maintained with oral and topical routes
What's normal
- No resistance development expected — membrane disruption mechanism resists adaptation
- Sustained immunomodulatory effects with continued exposure
- Anticancer activity in preclinical models typically assessed at 2-4 week endpoints
- Research outcomes ready for analysis
What's next
- Compile research data and assess endpoints
- Consider protocol modifications for future studies
- Evaluate potential for synthetic analog development based on RRWQWR motif
- Plan follow-up studies addressing salt-sensitivity limitations for clinical translation
Signs it's working
Treatment Response
- Improvement in the primary symptoms or condition being treated
- Positive changes in relevant lab values or clinical markers
- Consistent, stable response to Lactoferricin B over time
- Reduction in symptom frequency or severity
General Well-being
- Improved energy levels and daily functioning
- Better quality of life related to the treated condition
- Manageable or absent side effects indicating good tolerance
- Positive feedback from healthcare provider during check-ups
Not seeing results? Common reasons
- Not at therapeutic dose yet—initial doses are for building tolerance, not maximum effect
- Insufficient time at target dose—most compounds need several weeks to show full benefits
- Inconsistent dosing schedule—regular, consistent use is crucial for optimal results
- Individual variation in response—genetics, metabolism, and other factors affect outcomes
- Underlying conditions or medications interfering with absorption or effectiveness
- Improper storage leading to degraded product—always verify proper storage conditions
Key research
Questions
Frequently asked
Is lactoferricin the same as lactoferrin?
No. Lactoferrin is a large 80 kDa iron-binding glycoprotein found in milk, tears, saliva, and other body fluids. Lactoferricin B is a small 25-amino-acid peptide fragment that is released when bovine lactoferrin is cleaved by the digestive enzyme pepsin in the stomach. Importantly, lactoferricin B is 10-100 times more potent as an antimicrobial than intact lactoferrin. When you take a lactoferrin supplement, your stomach acid and pepsin naturally generate lactoferricin during digestion.
Why is it called lactoferricin 'B' — is there an 'H' version?
Yes. The 'B' stands for bovine (cow). Lactoferricin H is the human equivalent, derived from human lactoferrin residues 1-47. However, lactoferricin H has a significantly different amino acid sequence and generally weaker antimicrobial activity compared to the bovine form. Most research has focused on lactoferricin B because of its greater potency and the abundance of bovine lactoferrin as a starting material.
What makes the RRWQWR motif so important?
The hexapeptide RRWQWR (Arg-Arg-Trp-Gln-Trp-Arg) within lactoferricin B has been identified through systematic truncation and mutagenesis studies as the minimal sequence required for antimicrobial and anticancer activities. The two arginine residues provide positive charge for electrostatic membrane binding, while the two tryptophan residues provide the hydrophobic anchoring needed for membrane insertion. This motif has been used as a template for designing shorter, more potent synthetic antimicrobial peptides.
Why is salt sensitivity a problem for lactoferricin?
Lactoferricin B's antimicrobial activity is substantially reduced at physiological salt concentrations (150 mM NaCl) because sodium and chloride ions screen the electrostatic interactions between the cationic peptide and anionic bacterial membranes. This means in vitro activity at low-salt conditions may not fully translate to activity in blood, wound fluid, or other body fluids with physiological salt levels. This is the major barrier to clinical development and the focus of synthetic analog design efforts.
Does eating dairy products give you lactoferricin?
Yes, to some extent. Bovine lactoferrin is present in cow's milk, especially colostrum and whey. During normal digestion, stomach acid and pepsin cleave lactoferrin to release lactoferricin B. However, the amount generated from normal dietary intake is relatively small compared to research doses. Lactoferrin supplements (typically 100-500 mg) provide a more concentrated source. Interestingly, infant formula supplemented with bovine lactoferrin has been studied for its protective effects against neonatal infections.
Can lactoferricin help with cancer?
Preclinical research shows promising selective anticancer activity. Lactoferricin B, particularly in tetrameric (four-copy linked) form, shows cytotoxicity against breast cancer (MCF-7 IC50 22 µM), leukemia, fibrosarcoma, and neuroblastoma cells. The selectivity comes from cancer cells exposing anionic phosphatidylserine on their outer membrane, which normal cells keep hidden on the inner leaflet. However, all evidence is preclinical — no human clinical trials for cancer have been conducted with lactoferricin.
Further reading
History & related research
History · since 1992
Nature's Antibiotic Hidden in Mother's Milk
Lactoferricin is a tiny protein fragment found in all mammal milk. Scientists discovered it in 1992 and realized it's more powerful than the original protein it comes from.
Read the full history of Lactoferricin BReady for the protocol?
Every dosing tier, administration route, timing note, and dose-adjustment rule for Lactoferricin B, on one page.