01Research Directions

L-Histidine HCl Monohydrate research directions

01Research Directions

Why this compound has a literature

L-Histidine is an essential amino acid whose imidazole side chain, with a pKa near 6.0, gives it functions no other proteinogenic amino acid shares: it is the histidine moiety of carnosine and related dipeptides, the precursor of histamine, a metal-coordinating residue, and one of the most widely used buffering excipients in biopharmaceutical formulation. As a result the literature splits into two nearly non-overlapping halves — nutritional and metabolic research on one side, protein-formulation science on the other — and buyers of this material may be operating in either.

02Literature

What the literature investigates

Carnosine synthesis: which precursor is rate-limiting

This is the question most directly relevant to anyone formulating a beta-alanine stack. Boldyrev, Aldini and Derave (2013) reviewed carnosine physiology in Physiological Reviews and identified L-histidine, specifically its imidazole moiety, as the prime bioactive component of the dipeptide, with beta-alanine mainly regulating the rate of synthesis. Blancquaert et al. (2017) then tested this directly: thirty participants received 6 g/day beta-alanine, 3.5 g/day L-histidine, or both for 23 days, with muscle carnosine measured by magnetic resonance spectroscopy and biopsy. Both beta-alanine arms increased carnosine in all muscles examined with no difference between them, while the histidine-only arm showed no change — confirming beta-alanine as rate-limiting. Notably, histidine fell 30.6% in plasma and 31.6% in muscle in the beta-alanine-only group, and co-supplementation prevented that decline; the authors stated the significance of the decline remains to be determined.

Metabolic and clinical supplementation trials

Feng et al. (2013) reported a randomised double-blinded placebo-controlled trial in Diabetologia in which 100 obese women aged 33-51 with metabolic syndrome received 4 g/day histidine or placebo for twelve weeks; the authors reported reductions in HOMA-IR, BMI, waist circumference, fat mass, serum non-esterified fatty acids and inflammatory cytokines relative to placebo. Menon et al. (2020) meta-analysed thirty studies of histidine-containing dipeptides in Obesity Reviews, pooling twenty-three, and reported lower waist circumference and HbA1c at follow-up versus controls, with trends toward lower fat mass and insulin resistance. Thalacker-Mercer and Gheller (2020) reviewed the intake literature, describing associations at 4.0-4.5 g/day and noting reported adverse effects at high intakes above roughly 24 g/day. These are modest-sized trials in specific populations and should not be read as generalising to healthy adults.

Histidine as a biopharmaceutical excipient

Lv et al. (2024) published what they describe as the first dedicated review of histidine in protein biopharmaceuticals, in the International Journal of Pharmaceutics. It reports that the side-chain pKa of approximately 6.0 has made histidine the buffering agent of choice for the pH 5.5-6.5 range, catalogues commercial histidine-containing protein products, and surveys its documented roles as stabiliser, cryo- and lyo-protectant, antioxidant, viscosity reducer and solubilising agent, drawing comparisons with sugars such as sucrose and trehalose. The review also discusses complications specific to histidine systems, including the Donnan effect during diafiltration of monoclonal antibody solutions and the degradation of polysorbates in histidine buffer. For a supplier, this is the application in which trace metals, endotoxin and residual solvents matter most, since histidine coordinates metal ions.

Intake ceilings and amino acid interactions

Because histidine is often supplied in free-form blends alongside eight or more other amino acids, the interaction literature is directly relevant. Holeček (2022) reviewed side effects of amino acid supplements in Physiological Research and discussed competition for shared membrane carriers and for degradative enzymes as consequences of raising the intake of a single amino acid. Thalacker-Mercer and Gheller (2020) separately noted the adverse-effect threshold cited above. Read together, these papers indicate that the practical question in a multi-amino-acid formula is not the histidine dose in isolation but its ratio to the other amino acids sharing the same transport systems — a point the single-ingredient trials, by design, do not address.

03Specification

What this means when you specify the material

The monohydrate hydrochloride grade delivers roughly 83% histidine base, whereas published trials dosed free histidine (3.5-4.5 g/day in the carnosine and metabolic studies), so a salt-basis conversion is needed before a formula is compared to any protocol. In beta-alanine stacks the co-supplementation study used 3.5 g/day histidine against 6 g/day beta-alanine. For buffer and biopharmaceutical applications, the salt form determines both pH and chloride load, and trace-metal, endotoxin and heavy-metal limits become the governing specification rather than assay alone.

04References

Cited literature

Research context only. Each entry describes what a published study examined and reported. These are not claims about this raw material, and not claims about any finished product. Regulatory and labelling judgements belong to the brand placing the product on its market.

A physiological review of carnosine identified L-histidine, and specifically its imidazole moiety, as the prime bioactive component of the dipeptide, with beta-alanine mainly regulating the rate of carnosine synthesis. Boldyrev AA, Aldini G, Derave W. Physiol Rev. 2013;93(4):1803-1845. PMID 24137022 DOI 10.1152/physrev.00039.2012
In thirty participants supplemented for 23 days with 6 g/day beta-alanine, 3.5 g/day L-histidine, or both, muscle carnosine increased in all muscles examined in both beta-alanine arms with no difference between them and was unchanged in the histidine-only arm; histidine fell 30.6% in plasma and 31.6% in muscle in the beta-alanine-only group, which co-supplementation prevented. Blancquaert L, Everaert I, Missinne M, et al. Med Sci Sports Exerc. 2017;49(3):602-609. PMID 28106620 DOI 10.1249/MSS.0000000000001213
In a randomised double-blinded placebo-controlled trial, 100 obese women aged 33-51 with metabolic syndrome received 4 g/day histidine or placebo for twelve weeks; the authors reported reductions in HOMA-IR, BMI, waist circumference, fat mass, serum non-esterified fatty acids and inflammatory cytokines relative to placebo. Feng RN, Niu YC, Sun XW, et al. Diabetologia. 2013;56(5):985-994. PMID 23361591 DOI 10.1007/s00125-013-2839-7
A systematic review of thirty studies with twenty-three pooled for meta-analysis reported lower waist circumference and HbA1c at follow-up in histidine-containing dipeptide groups compared with controls, with trends toward lower fat mass and insulin resistance. Menon K, Marquina C, Liew D, Mousa A, de Courten B. Obes Rev. 2020;21(3):e12975. PMID 31828942 DOI 10.1111/obr.12975
A review of histidine intake reported that supplementation at 4.0-4.5 g/day and increased dietary histidine intake have been associated with lower BMI, adiposity, markers of glucose homeostasis, pro-inflammatory cytokines and oxidative stress, and noted that studies report adverse effects at high intakes above roughly 24 g/day. Thalacker-Mercer AE, Gheller ME. J Nutr. 2020;150(Suppl 1):2588S-2592S. PMID 33000165 DOI 10.1093/jn/nxaa229
A review of histidine in protein-based biopharmaceutical formulations reported that its side-chain pKa of approximately 6.0 has made it a primary buffering agent for pH 5.5-6.5, catalogued commercial histidine-containing protein products, and surveyed its documented roles as stabiliser, cryo- and lyo-protectant, antioxidant, viscosity reducer and solubilising agent, alongside complications such as the Donnan effect during diafiltration and polysorbate degradation in histidine buffer. Lv JY, Ingle RG, Wu H, Liu C, Fang WJ. Int J Pharm. 2024;662:124472. PMID 39013532 DOI 10.1016/j.ijpharm.2024.124472
A review of the side effects of amino acid supplements examined histidine among other amino acids and discussed competition for shared membrane carriers and degradative enzymes at high intakes. Holeček M. Physiol Res. 2022;71(1):29-45. PMID 35043647 DOI 10.33549/physiolres.934790

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