Reference
Key terms you’ll encounter across peptide research.
A
A molecule chemically derived from a single amino acid but not itself a peptide (no peptide bonds). L-Carnitine (from lysine and methionine) and creatine (from three amino acids but not linked by peptide bonds) are examples. Generally small and orally bioavailable.
B
Sterile water containing 0.9% benzyl alcohol, used to reconstitute lyophilized peptides. The benzyl alcohol inhibits bacterial growth, allowing the solution to be used for multiple doses over 28 days when refrigerated.
The fraction of an administered compound that reaches systemic circulation in active form. Peptides are typically degraded by digestion, which is why most are administered by injection rather than orally.
C
A compound that supplies choline for acetylcholine synthesis in the brain. Alpha-GPC and CDP-choline are the two most common nootropic forms. Choline itself is a quaternary amine, not a peptide.
Phase I trials test safety and dosing in small healthy cohorts. Phase II assesses efficacy in a target population. Phase III is large-scale efficacy testing, typically required for FDA approval.
A non-protein organic molecule required for an enzyme's activity. NAD+ and CoQ10 are coenzymes central to mitochondrial respiration. Often derivatives of vitamins. Not peptides.
A custom formulation containing multiple active ingredients, mixed by a compounding pharmacy. Formulation can vary by pharmacy. GLOW, KLOW, Lipo-C, and Trinity are compounded blends stacking different peptides or lipotropic agents.
Section 503A of the FD&C Act allows state-licensed pharmacies to prepare custom formulations for individual patients. The FDA maintains a Negative List of bulk substances that cannot be used under 503A.
D
Two or more drugs used together for complementary effects, rather than a fixed-dose combination product. Dasatinib + Quercetin (D+Q) is a common senolytic protocol; each acts on different senescent cell populations.
F
A list of bulk drug substances that the FDA has determined cannot be used for compounding under Section 503A. Several research peptides (including BPC-157) were added in 2023–2024.
A class of plant polyphenol (subclass of flavonoids) including quercetin, fisetin, kaempferol, and myricetin. Many have antioxidant and, in some cases, senolytic activity. Not peptides; they're small plant-derived molecules.
G
A molecule structurally similar to GABA (the brain's main inhibitory neurotransmitter) that modulates GABA-A or GABA-B receptors or voltage-gated calcium channels. Phenibut, gabapentin, and pregabalin are GABA analogs. Carries dependence risk with chronic use.
Growth Hormone-Releasing Peptides or Secretagogues. Short peptides that stimulate the pituitary ghrelin receptor to trigger endogenous GH release. Examples: Ipamorelin, GHRP-2, GHRP-6.
Glucagon-like peptide-1. An incretin hormone released from intestinal L-cells that promotes insulin secretion, slows gastric emptying, and reduces appetite. Synthetic analogs include semaglutide and tirzepatide.
A hormone built from a protein backbone with carbohydrate (glycan) side chains attached. HCG, LH, FSH, and TSH are the classic examples. The glycosylation affects half-life and receptor specificity. Technically proteins, not peptides.
I
Insulin-like Growth Factor 1. Produced primarily by the liver in response to GH, IGF-1 mediates most of GH's anabolic effects and is the primary biomarker for titrating GH-axis interventions.
Administration via injection directly into muscle tissue, allowing faster absorption than SubQ. Common sites include deltoid, thigh, and glute.
Administration via the nasal mucosa, often used for peptides that need direct CNS access (e.g., Semax, Selank). Bypasses first-pass metabolism.
L
Freeze-dried. Most research peptides are shipped as lyophilized powder to preserve stability and are reconstituted with BAC water before use.
M
A large (~150 kDa) immunoglobulin protein engineered to bind a specific target. Not a peptide. Administered by injection or infusion because antibodies are destroyed by digestion. Bimagrumab is an example: an anti-ActRII antibody developed for muscle wasting and obesity.
P
A short chain of amino acids (typically 2–50) linked by peptide bonds. Shorter than proteins. Many act as signaling molecules in the body: hormones, neurotransmitters, growth factors. BPC-157 (15 aa), semaglutide (31 aa), and thymosin α-1 (28 aa) are all peptides.
A broad family of plant-derived compounds containing multiple phenol rings, including flavonoids, lignans, and tannins. Urolithin A is a gut-microbiome-derived polyphenol metabolite that induces mitophagy.
A long chain of amino acids (typically 50+) that folds into a three-dimensional structure. Proteins are too large to pass through cell membranes passively and generally have their own receptor or signaling machinery. Klotho (~130 kDa) and HCG (237 aa, glycosylated) are technically proteins, not peptides, even though they're often grouped alongside peptides in clinical contexts.
Many hormones, including GH, are released in pulses rather than continuously. Preserving pulsatile release is a design goal for many GH-axis peptides to mimic physiology.
R
The process of dissolving lyophilized peptide powder in BAC water or sterile saline to produce an injectable solution. Reconstitution ratios determine dosing volume.
S
A low-molecular-weight (<900 Da) organic compound, the chemical class most conventional drugs belong to. Distinguished from peptides and proteins by being synthesized from scratch rather than built from amino acids. Most small molecules can be taken orally and cross cell membranes. Tadalafil, rapamycin, and MK-677 are small molecules that appear in this database because they're discussed alongside peptides.
Administration via injection into the fatty tissue just under the skin, typically in the abdomen or thigh. Slower absorption than IM but easier for self-administration.
A compound that mimics the effect of the sympathetic nervous system (adrenaline/noradrenaline signaling). Produces stimulant effects: raised heart rate, blood pressure, alertness, appetite suppression. DMAA is a sympathomimetic; it's not a peptide and was banned from US supplements by the FDA in 2013.
T
An enzyme that adds repetitive DNA sequences to chromosome ends (telomeres), counteracting telomere shortening. Target of longevity research including peptides like Epitalon.
The gradual increase of a drug's dose to reach a therapeutic range while minimizing side effects. Required for all GLP-1 analogs to manage GI tolerability.
W
The World Anti-Doping Agency maintains a list of substances and methods prohibited in athletic competition. Many peptides (TB-500, GH secretagogues, GHRH analogs) are banned at all times.
This site is for educational and research purposes only. It does not constitute medical advice. Always consult a qualified healthcare provider before using any peptide or supplement.