Study On The Gastrointestinal Absorption Characteristics Of 4-Hydroxybenzaldehyde In Rats

Objective:Our previous studies have shown that 4-hydroxybenzaldehyde（4-HBd）is one of the main active components of Gastrodia elata for brain protection.It was absorbed quickly and can reach the peak of blood concentration after intragastric administration for 4 min in rats,in order to further clarify the absorption characteristics of 4-HBd in rats.In this study,we used microdialysis sampling technology and high performance liquid chromatography（HPLC）to evaluate the absorption site and gastrointestinal absorption kinetics characteristics in rats after intragastric administration.Methods:1.Study on the absorption site of 4-HBd in rats4-HBd（400 mg/kg）were given to rats by intragastric administration immediately after gastric pylorus ligation surgery.And then,blood was sampled from the jugular vein by microdialysis in different time.The concentration of 4-HBd in blood at different time points was analyzed by HPLC.Based on these data,we drew the drug concentration-time curve and obtained the pharmacokinetic parameters.After comparing with the rats without gastric pylorus ligation surgery,the absorption site of4-HBd is clear in rats.2.Study on the absorption characteristics of 4-HBd in the stomach of rats2.1.Study on the stability of 4-HBd in gastric perfusionThe stability of 4-HBd in gastric perfusion solution was studied at 37±0.5℃,using gastric perfusion solution as the reaction medium to simulate the internal environment.2.2.Study on the absorption characteristics of 4-HBd in the stomach of ratsThe gastric absorption kinetic characteristics of 4-HBd were investigated using a in-situ gastric perfusion model in rats.The absorption doses of 4-HBd in different concentrations（25.2,50.1 and 100μg/mL）were investigated to study the absorption characteristics in the stomach of rats.3.Study on the absorption characteristics of 4-HBd in the intestinal of rats3.1.Study on the stability of 4-HBd in intestinal perfusionThe stability of 4-HBd in intestinal perfusion solution was studied at 37±0.5℃,using intestinal perfusion solution as the reaction medium to simulate the internal environment.3.2.Study on the absorption characteristics of 4-HBd in the intestinal of ratsThe in situ intestinal perfusion model of rats was used to investigate the intestinal absorption kinetic characteristics of 4-HBd.The absorption rate constant（Ka）,absorption half-life(t_1/2)and absorption capacity（P）of 4-HBd in different concentrations（25.22,50.83,and 99.52μg/mL）were investigated to study the absorption characteristics in the intestine of rats.Results:1.Study on the absorption site of 4-HBd in ratsAfter intragastric administration of 4-HBd（400 mg/kg）,the AUC_（0-∞）of rats without gastric pylorus ligation surgery was 59136.817±16477.996μg·L^-1·min,T_maxax was 4min,and C_maxax was 6748.845±1163.218μg·L^-1;the AUC_（0-∞）of rats undergoing gastric pylorus ligation surgery was 140478.893±48298.725μg·L^-1·min,T_maxax was 20min,and C_maxax was 1846.062±694.569μg·L^-1.The results showed that AUC_（0-∞）increased（P<0.01）,T_maxax prolonged and C_maxax decreased after pylorus ligation surgery（P<0.001）.It indicated that 4-HBd was absorbed in both stomach and intestine of rats.2.Study on the absorption characteristics of 4-HBd in the stomach of rats2.1.Study on the stability of 4-HBd in gastric perfusionUnder the condition of water bath at 37±0.5℃,the concentration of 4-HBd did not change before and after incubation in gastric perfusion,which indicated that it can exist stably in gastric perfusion in 2 h.2.2.Study on the absorption characteristics of 4-HBd in the stomach of ratsThe results of in situ gastric perfusion in rats showed that the absorption of 4-HBd at a concentration of 25.2μg/mL in the stomach of rats was 74.78±1.63μg;the absorption of 4-HBd at a concentration of 50.1μg/mL was 135.11±17.4μg;the absorption of 4-HBd at a concentration of 100μg/mL was 313.99±26.04μg.The absorbed dose in stomach increased along with the increase of the dose administrated（P<0.001）.The dose absorption of 4-HBd in the stomach was directly proportional to the dose administered.It suggested that 4-HBd is absorbed by passive transport in stomach in rats.3.Study on the absorption characteristics of 4-HBd in the intestinal of rats3.1.Study on the stability of 4-HBd in intestinal perfusionUnder the condition of water bath at 37±0.5℃,the concentration of 4-HBd did not change before and after incubation in intestinal perfusion,which indicated that it can exist stably in intestinal perfusion in 2 h.3.2.Study on the absorption characteristics of 4-HBd in the intestinal of ratsThe results of in situ perfusion of rat intestine showed that the Ka of 4-HBd at a concentration of 25.2μg/mL was 0.50±0.15 h^-11 for 2 hours in rat intestine,t_1/2/2 was1.48±0.43 h,P was 1925.69±197.07μg;the Ka of 4-HBd at a concentration of 50.83μg/mL was 0.58±0.12 h^-1,t1/2 was 1.24±0.24 h,P was 3981.61±462.52μg;the Ka of4-HBd at a concentration of 99.52μg/mL was 0.28±0.08 h^-1,t1/2 was 2.64±0.80 h,P was 4742.11±1071.10μg.In the concentration range of 25.22-50.53μg/mL,The absorbed dose of 4-HBd in intestine increased along with the increase of the dose administrated（P<0.001）.However,there is no significant difference between 50.83μg/mL and 99.52μg/mL 4-HBd（P>0.05）.In addition,the Ka of 4-HBd（99.52μg/mL）decresed（P<0.001）.These indicated that the absorption of 4-HBd in the intestine of rats was saturated under the given conditions.Therefore,It suggested that the absorption mode of 4-HBd in intestine may be active transport.Conclusions4-HBd is absorbed both in stomach and intestines in rats after intragastric administration.It is absorbed by passive transport in stomach and by active transport in intestines probably.