OBJECTIVE To prepare patchouli oil enteric-coated dropping pills, evaluate its colon-targeted release behaviors and therapeutic potency against rat ulcerative colitis(UC).

METHODS The single factor combined with response surface optimization method was used to screen matrix types and optimize preparation process parameters. Formula and thickness of Eudragit coating was selected based on dissolution tendency toward simulated intestinal fluids. Finally, colon targeting release behavior and the therapeutic effect of the preparation were assessed on the rat UC model induced by 2,4,6-trinitrobenzene sulfonic acid(TNBS).

RESULTS The optimal prescription of patchouli oil dropping pills was patchouli oil∶PEG6000∶PEG8000 ratio of 1∶1∶1; and the optimal condition for preparing patchouli oil pills was keeping nozzle temperature at 9 ℃, and dropping pills at the speed of 33 drops·min⁻¹, with dropping distance set at 6 cm; the optimal ratio of Eudragit L100∶Eudragit S100 was 3∶7 for preferential release in simulate intestinal fluid over simulated gastric fluid. Compared with free patchouli oil, patchouli oil enteric-coated dropping pills significantly alleviated the pathological symptoms such as weight loss, hematochezia and colon shortening in rats; the expression of pro-inflammatory cytokines IL-6, IL-1β, and IL-23 in serum was significantly down-regulated and the expression of anti-inflammatory cytokines IL-10 and TGF-β1 was significantly up-regulated. The mRNA expression of Mucin-1 and Mucin-2 in colon tissue was significantly up-regulated and the mRNA expression of inflammatory cytokines IL-6, IL-1β, and TNF-α was significantly down-regulated.

CONCLUSION The patchouli oil enteric-coated dropping pills have colon-targeted release ability and improve the anti-inflammatory effect of drugs.