Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-27. ← Back to Evidence Library
Rubiscolin-6 (YPLDLF): what the evidence says
At a glance
What it is: a six-amino-acid peptide (Tyr-Pro-Leu-Asp-Leu-Phe) from the spinach enzyme Rubisco that selectively activates delta-opioid receptors. R1
What the evidence says: in mice it reduced pain, R1 improved memory consolidation, R2 reduced anxiety-like behavior R3 and increased food intake, including when taken by mouth. R4
Biggest risks: unknown in people. It acts on opioid receptors.
Rating
| Human Human evidence | None |
| Animal Animal / lab evidence | Mouse studies R1, R2, R3, R4 |
| Regulatory | Not FDA-approved · not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page R5, R6, R7 · not named by WADA R8 |
| Established human dose | No |
Evidence verdict: Any human use: Unknown (zero human trials) · Memory, anxiety, appetite: mouse only
This page reports what studies used. It is not dosing advice.
Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source
About the evidence: all data are from mice and cells. The doses that worked in mice were large, and no one has tested it in people.
What is it?
Related pages: Kyotorphin, Selank, Dihexa.
Does it work?
- Animal Pain relief in mice (brain and oral dosing). R1
- Animal Memory consolidation, blocked by a delta antagonist. R2
- Animal Anxiety-like behavior reduced in mice. R3
- Animal Oral activity and appetite effects reviewed. R4
- Unknown No human trials.
Is it safe?
- Unknown No human safety data.
Gray-market vials: extra risks
A gray-market vial has no quality control and no guarantee of identity, strength or sterility. We test retail vials blind under the Open Peptide Standard; see /tests/. A passing test covers one batch on one date and does not mean the compound is safe.
Is it legal?
- US: not FDA-approved; no Drugs@FDA application found (openFDA searched Oct 26, 2026).
- Compounding: not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page. R5, R6, R7
- Sport: not named on WADA's 2026 Prohibited List. R8
Study details
Study details
These are amounts researchers used, not recommendations.
| Study | People / model | Route | Amount used | Follow-up | Reported | Citation |
|---|---|---|---|---|---|---|
| Yang 2003 | ddY mice | ICV or oral | 3 nmol/mouse ICV; 100 mg/kg oral | Single dose | Better memory consolidation | PMID 12668220 |
| Hirata 2007 | Mice | IP or oral | 10 mg/kg IP; 100 mg/kg oral | Single dose | Less anxiety-like behavior | PMID 17766012 |
Full reference list (PubMed, CT.gov, FDA and WADA checked Oct 26, 2026)
- R1 Yang S, et al. FEBS Lett. 2001. PMID 11741591
- R2 Yang S, et al. Peptides. 2003. PMID 12668220
- R3 Hirata H, et al. Peptides. 2007. PMID 17766012
- R4 Karasawa Y, et al. Int J Mol Sci. 2023. PMID 37373107
- R5 FDA, 503A bulk drug substances categories list (updated May 14, 2026). https://www.fda.gov/media/94155/download
- R6 FDA, 503B bulk drug substances categories list (updated Mar 21, 2025). https://www.fda.gov/media/94164/download
- R7 FDA, Certain bulk drug substances for use in compounding that may present significant safety risks (content current Apr 22, 2026). https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
- R8 WADA. The 2026 Prohibited List, full list checked; compound not named. https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
Disclaimer
This page is for education and harm reduction, not medical advice or a recommendation to use Rubiscolin-6 (YPLDLF). This compound is not FDA-approved. Any product sold under this name in the US is unregulated. Report problems to FDA MedWatch (https://www.fda.gov/safety/medwatch).