| Objective: In this study, the total lactones from Andrographis paniculata （TLA） waschosen as the model drug to prepare the TLA-SLN with central composite design-responsesurface methodology （CCD-RSM）. The possibility of SLN as oral delivery carrier of TLAwas investigated through the experiments in vivo and in vitro, including entrapmentefficiency, drug loading, particle size, ζ potential, stability, in vitro release, the transportmechanism in Caco-2monolayer cell model, pharmacokinetics and pharmacodynamics oflipid-lowering activity. Methods: Based on the andrographolide, neoandrographolide,14-deoxy-andrographolide, dehydroandrographolide from TLA, the HPLC method fordetermination of drug loading and entrapment efficiency was established, and optimizedthe preparation of TLA-SLN with CCD-RSM. The quality evaluation of the TLA-SLNand lyophilized powder was investigated by appearance, particle size, ζ potential, pH anddifferential scanning calorimetry （DSC）. The dialysis tubing was used to explore therelease degree of the TLA solution and suspension, TLA-SLN suspension and lyophilizedpowder in vitro. LC-MS was used in quantitative analysis of TLA-SLN in rat serum in thepharmacokinetics experiment in vivo. UPLC-MS was used in quantitative analysis ofTLA-SLN in cell-culture medium to study the transport mechanism in Caco-2monolayercell model. The experimental hyperlipemia model was set up with75%egg yolkemulsions to investigate the lipid-lowering activity of the TLA-SLN. Results: Theoptimized preparation of TLA-SLN was ratios of drug to lipid of10%, lecithin to lipid of1.25, and tween-80of4%. The appearance of TLA-SLN was round with mean particlesize of322.67±2.50nm, polydispersity index was0.25±0.03, ζ potential was-27.98±1.19mV, pH was5.10±0.01, characteristic absorption peak changed and appeared in47.5℃in DSC. The results of stability experiments indicated that the stability of TLA-SLNsuspension was poor, while the TLA-SLN lyophilized powder was improved. The resultsof stability experiments focused on the irrigating solution of segment of different intestine indicated that TLA could transformed free in the duodenum, while the TLA-SLN wasenhanced. In the study of release characteristics in vitro, the TLA solution could bereleased （97.86±9.78）%in8h, while suspension was just released （65.83±9.46）%in24h. TLA-SLN and lyophilized powder were released completely after24h. The resultssuggested that SLN could increase solubility and delayed release rate. Compared withTLA, the results of the pharmacokinetics experiment in vivo showed that TLA-SLNsignificantly enhanced the absorption and oral bioavailability with the Cmaxof23.06±12.27ng·mL-1versus4.00±1.94ng·mL-1for AND in rats, and the relative bioavailabilitywas402.62%for AND. The Cmaxof NEO from oral TLA-SLN was34.43±21.34ng·mL-1,which was significant higher than that of oral TLA （5.75±3.45ng·mL-1）（P<0.05）, andthe relative bioavailability was400.51%for NEO. The Cmaxof DEH from oral TLA-SLNwas130.25±62.98ng·mL-1, which was significant higher than that of oral TLA （25.18±16.12ng·mL-1）（P<0.05）, and the relative bioavailability was1593.18%for DEH. TheCaco-2cell model was used to study the uptake and transport mechanism and the resultsdemonstrated that the Papp of AND from TLA-SLN was （8.94±0.45）×10-6cm·s-1, whichwas significant higher than that of mix-standard （5.77±0.05）×10-6and that of TLA （6.63±0.78）×10-6cm·s-1（P<0.01）, respectively. The Papp of DEH from TLA-SLN was （10.71±0.58）×10-5cm·s-1, which was significant higher than that of mix-standard （6.18±0.20）×10-5cm·s-1and that of TLA（6.39±0.20）×10-5cm·s-1（P<0.01）, respectively. Theresults of pharmacodynamics of lipid-lowering activity indicated that TLA-SLN couldsignificantly reduced the serum CHO, TG and LDL （P<0.05）, increased the serum HDLlevel in mice （P<0.05） after oral administration of TLA-SLN, compared with that of oraladministration of TLA. These findings showed that SLN couls improved thebioavailability of TLA. Conclusions: The experimental studies have shown that thecharacterics of poor dissolubility, poor stability and poor bioavailability of TLA could beimproved significantly by solid lipid nanospheres. The elevation of bioavailability andanti-hyperlipemia of TLA could achieved by improving the dissolubility and release,reducing the conversion of the TLA in the duodenum and affecting the transportingpattern of TLA, SLN is a potential new drug delivery system for TLA. |
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