Phosphodiesterase type 5 (PDE5) (IC50 = 0.64 μM)
Kuraridine has multiple biological targets. Its primary enzymatic target is phosphodiesterase type 5 (PDE5), which it inhibits with an IC50 of 0.64 microM. It shows 2.0- and 12.9-fold selectivity for PDE5 over PDE3 and PDE4, respectively. Additionally, it is a positive allosteric modulator (PAM) of GABAA receptors, potentiating the effect of GABA.

Kuraridine exhibits strong inhibitory action (IC50=0.64 μM) against cGMP PDE5, with selectivity over PDE3 and PDE4 being 2.0 and 12.9 times, respectively[1]. In the absence of GABA, kuraridine causes significant inward currents of chlorides. 10% of the maximum IGABA generated by a saturating GABA concentration (1 mM) is not exceeded by the currents[2]. Kuraridine causes concentration–response curves in Xenopus oocytes expressing GABAA receptors made up of α1, β2, and γ2S subunits, resulting in an increase in IGABA (EC50=4.0±2.4 μM)[2].

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During the search for naturally occurring cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5) inhibitors, it was found that the extracts from Sophora flavescens exhibit potent inhibitory activity against cGMP PDE5 prepared from rat diaphragm. Therefore, the inhibitory activities of five flavonoids, kushenol H (1), kushenol K (2), kurarinol (3), sophoflavescenol (4) and kuraridine (5), isolated from S. flavescens were measured against cGMP PDE5 to identify potent cGMP PDE5 inhibitory constituents. Among tested compounds, sophoflavescenol (4), a C-8 prenylated flavonol, showed the most potent inhibitory activity (IC(50)=0.013 microM) against cGMP PDE5 with 31.5- and 196.2-fold selectivity over PDE3 and PDE4, respectively. Kinetic analysis revealed that sophoflavescenol was a mixed inhibitor of PDE5 with a K(i) value of 0.005 microM [1].

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In vitro, Kuraridine is a potent PDE5 inhibitor. It induces pronounced chloride inward currents in Xenopus oocytes expressing GABAA receptors in the absence of GABA, acting as an allosteric agonist. It also enhances the IGABA response with an EC50 of 4.0 +/- 2.4 microM in the presence of GABA. It also influences cell proliferation and induces apoptosis in various cancer cell lines.

In vivo data for Kuraridine is limited in these documents. While it has been identified as a PDE5 inhibitor, its in vivo vasodilatory effects have not been detailed. Its anti-tumor effects in cell lines suggest it may have activity in xenograft models. Its modulatory effect on GABAA receptors suggests it may have in vivo effects on the central nervous system.

Expression of GABAA receptors [2]
Stage V–VI oocytes from Xenopus laevis were prepared and cRNA was injected as previously described by Khom et al. Female X. laevis were anesthetized by exposing them for 15 min to a 0.2% MS-222 (methanesulfonate salt of 3-aminobenzoic acid ethyl) solution before surgically removing parts of the ovaries. Follicle membranes from isolated oocytes were enzymatically digested with 2 mg/mL collagenase. Synthesis of capped run-off poly(A+) cRNA transcripts was obtained from linearized cDNA templates (pCMV vector). One day after enzymatic isolation, the oocytes were injected with 50 nL of DEPC-treated water containing different cRNAs at a concentration of approximately 300–3000 pg/nL per subunit. To ensure expression of α1β2γ2S receptors, rat cRNA of α1,β2, and γ2S subunits were mixed in a 1:1:10 ratio. The amount of injected cRNA mixture was determined by means of a NanoDrop ND-1000. Oocytes were then stored at 18 °C in ND96 solution (90mM NaCl, 1mM KCl, 1mM MgCl2, 1 mM CaCl2, and 5 mM HEPES; pH 7.4) Voltage clamp measurements were performed between days 1 and 5 after cRNA injection.

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Two-microelectrode voltage clamp studies [2]
Electrophysiological experiments were performed by the two-microelectrode voltage clamp method making use of a TURBO TEC-03X amplifier at a holding potential of −70 mV and pCLAMP 10 data acquisition software. Currents were low-pass-filtered at 1 kHz and sampled at 3 kHz. ND 96 solution was used as bath solution. The electrode filling solution consisted of 2 M KCl. Oocytes with maximal current amplitudes >3 μA were discarded to exclude voltage clamp errors. Before application of test solutions, a dose–response experiment with GABA concentrations ranging from 0.1 to 1 mM was performed to determine GABA EC3–10 (typically between 3 and 10 μM).

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The non-cellular PDE5 inhibition assay protocol involves using a cGMP PDE5 enzyme prepared from rat diaphragm. Kuraridine and the enzyme are pre-incubated at 30degC for 10 minutes. The reaction is started by adding 3H-cGMP and is incubated for 20 minutes. The reaction is terminated, and the amount of 3H-5'-GMP product is quantified. IC50 values are calculated from the inhibition curves.

The cellular protocol for studying Kuraridine's effect on GABAA receptors uses Xenopus laevis oocytes. Oocytes are injected with cRNA encoding the human GABAA receptor alpha1, beta2, and gamma2S subunits. After 1-3 days, the oocytes are placed in a recording chamber and voltage-clamped at -60 mV. Kuraridine is applied via perfusion, and the resulting chloride inward currents are measured.

No specific in vivo animal protocol for Kuraridine is described. A typical in vivo protocol for a PDE5 inhibitor is to administer it to rats, either intravenously or orally, and then measure the blood pressure in the carotid artery and corpus cavernosum. An increase in intracavernous pressure relative to blood pressure indicates PDE5 inhibition.

No detailed pharmacokinetic data for Kuraridine is provided in these references. As a natural product extract, its absorption, distribution, metabolism, and excretion profile would be complex due to the presence of multiple compounds. Pure Kuraridine would be studied to determine properties like solubility, stability, and potential for oral bioavailability.

No specific toxicological data is available. However, Sophora flavescens has been used in traditional medicine, but it can contain alkaloids with known toxicity. For pure Kuraridine used in research, standard laboratory safety precautions should be followed, and it should be treated as a potentially hazardous compound until its toxicity profile is established.

[1]. A prenylated flavonol, sophoflavescenol: a potent and selective inhibitor of cGMP phosphodiesterase 5. Bioorg Med Chem Lett. 2002 Sep 2;12(17):2313-6.

[2]. HPLC-based activity profiling for GABAA receptor modulators from the traditional Chinese herbal drug Kushen (Sophora flavescens root). Mol Divers. 2011 May;15(2):361-72.

Kuraridin has been reported in Sophora flavescens, and relevant data are available.

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The ethyl acetate extract of Sophora flavescens root can enhance the influx of chloride ions induced by γ-aminobutyric acid (GABA) in Xenopus oocytes with GABA(A) receptors whose transient expression subunits are α(1)β(2)γ(2S). Based on high performance liquid chromatography (HPLC) activity analysis, 8-lavenderyl flavonoids, matrine I, matrine G, (-)-matrine and matrine were identified as GABA(A) receptor modulators. In addition, a series of structurally related inactive flavonoids were identified. Among them, matrine Y (4) was identified as a new natural product. 8-lavenderyl flavonoids are the first representatives of a new scaffold for this target. [2]

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Kuraridine is a unique research tool because it is a natural product with two distinct and relevant biological activities. Its ability to inhibit PDE5, a target for erectile dysfunction and pulmonary hypertension, and modulate GABAA receptors, a target for anxiety and sedation, makes it a "dirty drug" that can be used to study potential polypharmacology or to explore the effects of hitting multiple targets simultaneously.

C26H30O6

438.51

438.204

C, 71.21; H, 6.90; O, 21.89

34981-25-4

44428631

White to yellow solid powder

5.504

4

6

9

32

694

1

CC(=CC[C@H](CC1=C(C(=C(C=C1O)OC)C(=O)/C=C/C2=C(C=C(C=C2)O)O)O)C(=C)C)C

PIAPWPAWQGDOMN-SXAWMYDMSA-N

InChI=1S/C26H30O6/c1-15(2)6-7-18(16(3)4)12-20-23(30)14-24(32-5)25(26(20)31)21(28)11-9-17-8-10-19(27)13-22(17)29/h6,8-11,13-14,18,27,29-31H,3,7,12H2,1-2,4-5H3/b11-9+/t18-/m1/s1

(E)-1-[2,4-dihydroxy-6-methoxy-3-[(2R)-5-methyl-2-prop-1-en-2-ylhex-4-enyl]phenyl]-3-(2,4-dihydroxyphenyl)prop-2-en-1-one

34981-25-4; KURAIDIN; kuraridin; (E)-1-[2,4-dihydroxy-6-methoxy-3-[(2R)-5-methyl-2-prop-1-en-2-ylhex-4-enyl]phenyl]-3-(2,4-dihydroxyphenyl)prop-2-en-1-one; (E)-1-(2,4-dihydroxy-6-methoxy-3-((2R)-5-methyl-2-prop-1-en-2-ylhex-4-enyl)phenyl)-3-(2,4-dihydroxyphenyl)prop-2-en-1-one; CHEMBL243362; Z399B8AG6Z;

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)

DMSO: ≥ 100 mg/mL (228.04 mM)

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.

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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).

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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)

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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).

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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

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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.

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