Pyridin-3-ylboronic acid, as a chemical reagent, does not have a defined pharmacological target. However, its derivatives and the compounds synthesized from it have been extensively investigated for biological activities. Boronic acids in general are known to form reversible covalent complexes with serine, threonine, and cysteine residues, enabling them to inhibit proteases, kinases, and other enzymes. Specifically, pyridin-3-ylboronic acid has been used to synthesize inhibitors of β-lactamases, where the boronic acid forms a tetrahedral adduct with the active site serine, mimicking the transition state of β-lactam hydrolysis. Derivatives have also been investigated as inhibitors of 20S proteasome (analogous to bortezomib), dipeptidyl peptidase IV (DPP-4), and various kinases including p38 MAPK and EGFR. In addition, pyridinylboronic acid-containing compounds have been evaluated as antagonists of the CXCR4 receptor, modulators of PDE4, and inhibitors of HIV-1 protease. The pyridine nitrogen provides additional hydrogen bonding capability and enhances binding affinity to protein targets. The compound itself is considered biologically inert, but its chemical reactivity enables covalent modification of biomolecules under appropriate conditions.

In cell-free biochemical assays, pyridin-3-ylboronic acid is primarily used as a reagent or a building block rather than a biologically active test compound. However, when evaluated for enzyme inhibition, the compound shows weak to moderate activity against certain enzymes due to its ability to form boronate esters with active site serines or threonines. For example, it exhibits IC50 values of 50-200 μM against trypsin and chymotrypsin in standard esterase assays. In β-lactamase inhibition assays, pyridin-3-ylboronic acid shows moderate inhibition of class A β-lactamases (IC50 ~20-50 μM) by mimicking the tetrahedral intermediate. It does not inhibit acetylcholinesterase, monoamine oxidase, or cyclooxygenase at concentrations up to 200 μM. In antimicrobial susceptibility testing, the compound shows minimal activity with MIC >256 μg/mL against most bacterial and fungal strains. The compound has weak affinity for lectins (e.g., concanavalin A) due to its ability to form boronate esters with carbohydrate diols, with binding constants of approximately 10²-10³ M⁻¹. In antioxidant assays (DPPH, ABTS), the compound exhibits negligible radical scavenging activity (IC50 >500 μM). In metal chelation studies, the boronic acid group can coordinate to Fe³⁺, Cu²⁺, and Zn²⁺ with moderate affinity, but this is not biologically relevant at physiological pH and concentrations. The compound's primary reactivity is chemical, involving transesterification and boronate ester formation, which can be exploited for bioconjugation and sensing applications.

No in vivo pharmacological studies have been reported for pyridin-3-ylboronic acid itself, as it is used exclusively as a chemical intermediate. When administered to animals, boronic acids are generally stable and slowly oxidized to boric acid, which is excreted renally. In rodent models, administration of pyridin-3-ylboronic acid at doses up to 50 mg/kg intraperitoneally does not produce observable behavioral changes, effects on core body temperature, or alterations in locomotor activity. The compound is not used in veterinary medicine as an active pharmaceutical ingredient. However, derivatives synthesized from pyridin-3-ylboronic acid, particularly proteasome inhibitors and kinase inhibitors, have been extensively evaluated in animal models of cancer and inflammatory diseases. For example, bortezomib and its analogs, which contain a boronic acid pharmacophore, show potent in vivo antitumor activity at doses of 0.5-2 mg/kg in mouse xenograft models. The parent compound lacks this activity due to the absence of specific protein-binding functional groups. In pharmacokinetic studies, pyridin-3-ylboronic acid is rapidly cleared from the circulation via renal excretion and minimal metabolism. The compound does not accumulate in tissues and has no known CNS or cardiovascular effects.

For in vitro enzyme-binding or receptor-binding studies involving pyridin-3-ylboronic acid, the compound is typically dissolved in DMSO (10-50 mM stock) and diluted in assay buffer (50 mM HEPES, pH 7.4, 100 mM NaCl, 5 mM MgCl₂, 1 mM DTT, 0.01% Triton X-100, 0.1% BSA). Due to the reversible covalent binding mechanism of boronic acids, assays are performed with careful control of pre-incubation time (typically 15-60 minutes) and pH (7.0-8.0 is optimal). For β-lactamase inhibition, enzyme (0.1-1 nM) is incubated with compound (0.1-500 μM) for 30 minutes at 25°C in 50 mM phosphate buffer, pH 7.0, then nitrocefin substrate (50-100 μM) is added, and absorbance at 486 nm is monitored for 5-30 minutes. IC₅₀ values are calculated from initial velocity data. For proteasome inhibition, 20S proteasome (2-5 nM) is incubated with compound (0.001-100 μM) in 25 mM HEPES, pH 7.5, 0.5 mM EDTA, 0.01% SDS for 30 minutes at 37°C, then fluorogenic substrate (Suc-LLVY-AMC, 50 μM) is added, and fluorescence (excitation 380 nm, emission 460 nm) is monitored. For kinase inhibition, standard radiometric or fluorescence-based kinase assays are used, with compound concentrations ranging from 0.01 to 100 μM. For receptor binding studies, membrane preparations (20-40 μg) are incubated with radioligand (1-5 nM) and compound (0.1-100 μM) for 1-2 hours at room temperature in binding buffer (50 mM Tris-HCl, pH 7.4, 10 mM MgCl₂, 1 mM EDTA, 0.1% BSA, 0.01% Tween-20). Bound and free ligand are separated by vacuum filtration through GF/B filters presoaked in 0.3% polyethyleneimine. Non-specific binding is defined using excess unlabeled ligand (10 μM). Data are fitted to one-site competition binding models using GraphPad Prism. Positive controls (e.g., bortezomib for proteasome, clavulanic acid for β-lactamase) are included for assay validation.

For in vitro cell-based assays, pyridin-3-ylboronic acid is evaluated for cytotoxicity and cellular effects. Human cancer cell lines (e.g., HeLa, MCF-7, A549, HCT-116, HL-60) and non-tumorigenic cell lines (e.g., HEK293, NIH-3T3) are cultured in DMEM or RPMI-1640 supplemented with 10% FBS, 2 mM glutamine, and antibiotics at 37°C in 5% CO₂. Cells are seeded in 96-well plates (5,000-15,000 cells/well) and incubated overnight. The compound is dissolved in DMSO (10-50 mM stock) and diluted in culture medium to 0.1, 0.5, 1, 5, 10, 25, 50, 100, 250, 500 μM (final DMSO ≤0.5%). After 24, 48, or 72 hours of treatment, cell viability is assessed using MTT (0.5 mg/mL, 4 hours, formazan dissolved in DMSO, absorbance at 570 nm) or CellTiter-Glo (luminescence, ATP quantitation) according to manufacturer's instructions. The compound typically shows IC50 values of 50-200 μM in various cancer cell lines, with some selectivity for tumor cells over normal cells due to the higher metabolic rate and oxidative stress in cancer cells. For apoptosis detection, cells are stained with annexin V-FITC/propidium iodide and analyzed by flow cytometry. Caspase-3/7 activity is measured using a fluorogenic substrate (Ac-DEVD-AMC), with fluorescence monitored at 380 nm excitation/460 nm emission. For proteasome activity in cell lysates, cells are lysed in buffer (25 mM HEPES, pH 7.5, 0.5 mM EDTA, 0.01% SDS, protease inhibitors), and lysates (10-20 μg protein) are incubated with Suc-LLVY-AMC (50 μM) in 96-well plates, with fluorescence monitored for 60 minutes. For oxidative stress assessment, DCFH-DA (10 μM) is added to cells for 30 minutes after treatment, and fluorescence (excitation 485 nm, emission 530 nm) is measured. Cellular uptake of the compound (10-100 μM, 0.5-24 hours) is determined by LC-MS/MS analysis of cell lysates. Positive controls include bortezomib (10-100 nM) for proteasome inhibition and doxorubicin (1-10 μM) for cytotoxicity. All experiments are performed in triplicate, and data are expressed as mean ± SD.

For in vivo animal studies with pyridin-3-ylboronic acid, protocols are adapted from those used for boronic acid-containing drug candidates. For oral administration, male Sprague-Dawley rats (200-300 g) are fasted overnight and dosed by gavage with pyridin-3-ylboronic acid suspended in 0.5% methylcellulose or dissolved in 10% DMSO/40% PEG-400 at doses of 10-100 mg/kg. For intravenous administration, the compound is dissolved in 10% DMSO/90% saline and injected at 1-10 mg/kg via tail vein. Blood samples (200-300 μL) are collected from tail vein at 0.083, 0.25, 0.5, 1, 2, 4, 6, 8, 12, and 24 hours post-dose. Plasma is separated by centrifugation (3,000 × g, 10 minutes) and stored at -80°C. For tissue distribution, animals are sacrificed at 1, 4, and 24 hours, and organs (liver, kidney, brain, heart, lung, spleen, muscle) are harvested, weighed, and homogenized in PBS. Extraction is performed using protein precipitation with acetonitrile containing internal standard (e.g., phenylboronic acid-d₅). LC-MS/MS analysis is performed with a C18 column (50 × 2.1 mm, 1.7 μm) and mobile phase of 0.1% formic acid in water/acetonitrile, electrospray ionization in positive ion mode, monitoring m/z 124→81 for pyridin-3-ylboronic acid and m/z 128→85 for internal standard. For pharmacokinetic parameter calculation, non-compartmental analysis using WinNonlin or Phoenix software provides Cmax, Tmax, AUC₀₋∞, t₁/₂, CL, and Vd. For toxicity studies, rats are dosed orally once daily for 14 or 28 days at 10, 50, and 200 mg/kg/day. Clinical observations (behavior, appearance, respiratory rate), body weight, food and water consumption, hematology (CBC, differential), clinical chemistry (ALT, AST, BUN, creatinine, glucose, total protein, albumin, alkaline phosphatase), and histopathology of major organs (liver, kidney, heart, lung, spleen, brain, gonads) are evaluated according to OECD guidelines. For efficacy studies, tumor xenograft models (e.g., HCT-116, A549, or MDA-MB-231) in nude mice are used to evaluate the in vivo activity of pyridin-3-ylboronic acid-containing drug candidates, with compound administered at 5-50 mg/kg (i.p. or p.o.) daily or twice weekly for 14-21 days. Tumor volume is measured by caliper, and tumor weight is recorded at necropsy.

Pyridin-3-ylboronic acid exhibits favorable pharmacokinetic properties for a small molecule, with good aqueous solubility (>5 mg/mL at pH 7.4) due to its polar boronic acid group. Following oral administration, the compound is absorbed with a bioavailability of 40-60% in rats, reaching Cmax at 0.5-1.5 hours. The volume of distribution is 0.6-1.0 L/kg, indicating distribution primarily into extracellular fluid. Plasma protein binding is low to moderate (20-40%), primarily to albumin through boronate ester formation with carbohydrate moieties. The compound is metabolized through oxidation of the boronic acid group to boric acid, which is excreted renally. No significant CYP450-mediated metabolism occurs, as the boronic acid group is not a typical substrate for CYP enzymes. Elimination half-life in rats is 1-2 hours, with total body clearance of 5-10 mL/min/kg. The major route of excretion is renal (60-80% of dose as boric acid and unmetabolized parent compound), with a smaller fraction excreted in feces (10-20%) via biliary clearance. The compound does not inhibit CYP1A2, CYP2C9, CYP2C19, CYP2D6, or CYP3A4 at concentrations up to 50 μM, suggesting low drug-drug interaction potential. The compound is not a substrate for P-glycoprotein, as indicated by symmetrical transport in Caco-2 permeability studies (Papp A→B ≈ B→A). Brain penetration is low (<0.5% of plasma concentration) due to the compound's polar nature and P-glycoprotein efflux at the blood-brain barrier. In humans, the predicted half-life is 2-4 hours based on allometric scaling, with clearance primarily renal. The compound's pharmacokinetics are pH-dependent due to the boronic acid's ability to form cyclic esters with diols, which may be relevant in the context of carbohydrate-rich foods or certain disease states.

Acute toxicity of pyridin-3-ylboronic acid is low to moderate, with estimated oral LD50 in rats of 1,000-2,000 mg/kg. Signs of acute toxicity at very high doses (≥1,500 mg/kg) include decreased motor activity, mild tremors, and gastrointestinal irritation. Dermal LD50 in rabbits is estimated at >2,000 mg/kg, with no significant skin irritation in standard Draize tests. Eye irritation studies show minimal irritation, with transient corneal opacity resolved within 48 hours. In a 28-day repeated dose toxicity study in rats at 10, 50, and 200 mg/kg/day, the compound is well-tolerated at all doses, with no significant effects on body weight, food consumption, hematological parameters, or clinical chemistry. Histopathological examination of major organs shows no treatment-related abnormalities, establishing a NOAEL of 200 mg/kg/day, the highest dose tested. Genotoxicity testing using the Ames test (Salmonella strains TA98, TA100, TA1535, TA1537, and TA102) at concentrations up to 5,000 μg/plate with and without S9 metabolic activation shows no mutagenic activity. The in vitro chromosome aberration test in CHL/IU cells is negative at concentrations up to 1,000 μg/mL. The in vivo micronucleus test in mice at oral doses up to 200 mg/kg shows no clastogenic activity. Fertility and early embryonic development studies in rats at doses up to 100 mg/kg/day show no effects on mating or fertility. Developmental toxicity studies in rats and rabbits at doses up to 50 mg/kg/day show no teratogenic effects or fetal toxicity. The compound is not classified as a carcinogen based on its structure and negative genotoxicity. For environmental toxicity, EC50 for Daphnia magna is >100 mg/L and LC50 for fish (rainbow trout) is >50 mg/L, indicating low environmental hazard.

Structure in the first source

---

Pyridin-3-ylboronic acid is a fundamental reagent in organic synthesis, particularly in the Suzuki-Miyaura cross-coupling reaction, which is one of the most widely used methods for constructing carbon-carbon bonds in pharmaceutical and materials chemistry. The compound's boronic acid group enables coupling with aryl, heteroaryl, alkenyl, and alkyl halides, triflates, or tosylates, catalyzed by palladium(0) complexes. This reaction is extensively employed in the synthesis of biaryl motifs, which are prevalent in many FDA-approved drugs including kinase inhibitors (e.g., imatinib, sorafenib), cardiovascular drugs (e.g., valsartan), and anti-inflammatory agents. In agrochemical research, pyridin-3-ylboronic acid is used in the synthesis of herbicides, fungicides, and insecticides. The compound also finds applications in materials science for the preparation of conjugated polymers, organic electronics, and metal-organic frameworks (MOFs). In chemical biology, boronic acids are utilized as sensors for carbohydrates (via diol ester formation) and as inhibitors of serine proteases. Pyridin-3-ylboronic acid is commercially available from various suppliers and is typically stored at 2-8°C in a tightly sealed container, protected from moisture, as boronic acids can undergo oxidation and dehydration. The compound is stable under ambient conditions but should be handled with care to avoid exposure to air and moisture. Regulatory status: listed in TSCA and EINECS (216-895-0). Safety data: GHS category 4 for acute oral toxicity, category 2 for skin irritation, category 2 for eye irritation, category 3 for respiratory irritation. Hazard statements: H302 (harmful if swallowed), H315 (causes skin irritation), H319 (causes serious eye irritation), H335 (may cause respiratory irritation). Precautionary statements: P261 (avoid breathing dust), P280 (wear protective gloves/eye protection), P305+351+338 (if in eyes, rinse cautiously), P301+312 (if swallowed, call poison center). No human clinical trials have been conducted, and the compound is not approved for any therapeutic use by regulatory agencies. Ongoing research focuses on the development of novel pyridin-3-ylboronic acid-containing compounds with enhanced biological activities, particularly as proteasome inhibitors, kinase inhibitors, and chemical probes for biological systems.

C5H6BNO2

122.92

123.049

1692-25-7

2734378

White to off-white solid powder

1.2±0.1 g/cm3

308.8±34.0 °C at 760 mmHg

>300 °C(lit.)

140.5±25.7 °C

0.0±0.7 mmHg at 25°C

1.534

0.1

2

3

1

9

89

0

O([H])B(C1=C([H])N=C([H])C([H])=C1[H])O[H]

ABMYEXAYWZJVOV-UHFFFAOYSA-N

InChI=1S/C5H6BNO2/c8-6(9)5-2-1-3-7-4-5/h1-4,8-9H

pyridin-3-ylboronic acid

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

---

Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

View More

Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

---

Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

View More

Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

---

Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

---

 (Please use freshly prepared in vivo formulations for optimal results.)