RESUMO
Usnic acid (UA) has been studied by its pharmacological properties; however, it presents moderate toxicity, low solubility, and absorption by biological membranes. The aim of this study was to develop poly-ε-caprolactone microsphere polymers containing UA (UA-micro) and evaluate their acute toxicity and anti-inflammatory activity. The microspheres were prepared by multiple emulsion technique (water/oil/water) and characterized by the encapsulation efficiency, particle size, polydispersity index, and zeta potential. The acute toxicity of UA and UA-micro (25-50 mg/kg; p.o.) was evaluated in mice. The anti-inflammatory activity of UA and UA-micro was evaluated by subcutaneous air pouch and carrageenan-induced paw edema in rat, with measurement of inflammatory cytokines and MPO levels. The UA presented encapsulation efficiency of 97.72%, particle size of 13.54 micrometers, polydispersity index of 2.36, and zeta potential of 44.5 ± 2.95 mV. The UA-micro presented lower acute toxicity (LD50 value up to 2000 mg/kg; p.o.) when compared to UA. UA-micro and UA (25 mg/kg) significantly reduced paw volume and decreased MPO levels, whereas only UA-micro (50 mg/kg) reduced significantly IL-1ß, TNF-α, and NO levels in inflammatory exudate. These results suggest that controlled release systems, as microspheres, can be a promising alternative to reduce the toxicity of UA, making it a viable compound for inflammation therapy.
RESUMO
In this pioneer study, 2-hydroxypropyl-ß-cyclodextrin (HP-ß-CD) was used to improve the solubility of the diffractaic acid (DA) via inclusion complex (DA:HP-ß-CD). Subsequently, DA:HP-ß-CD was incorporated into poly-ε-caprolactone (PCL) microspheres (DA:HP-ß-CD-MS). Microspheres containing DA (DA-MS) or DA:HP-ß-CD (DA:HP-ß-CD-MS) were prepared using the multiple W/O/W emulsion-solvent evaporation technique. The phase-solubility diagram of DA in HP-ß-CD (10-50mM) showed an AL type curve with a stability constant K1:1=821M-1. 1H NMR, FTIR, X-ray diffraction and thermal analysis showed changes in the molecular environment of DA in DA:HP-ß-CD. The molecular modeling approach suggests a guest-host complex formation between the carboxylic moiety of both DA and the host (HP-ß-CD). The mean particle size of the microspheres were ∅DA-MS=5.23±1.65µm and ∅DA:HP-ß-CD-MS=4.11±1.39µm, respectively. The zeta potential values of the microspheres were ζDA-MS=-7.85±0.32mV and ζDA:HP-ß-CD-MS=-6.93±0.46mV. Moreover, the encapsulation of DA:HP-ß-CD into microspheres resulted in a more slower release (k2=0.042±0.001; r2=0.996) when compared with DA-MS (k2=0.183±0.005; r2=0.996). The encapsulation of DA or DA:HP-ß-CD into microspheres reduced the cytotoxicity of DA (IC50=43.29µM) against Vero cells (IC50 of DA-MS=108.48µM and IC50 of DA:HP-ß-CD-MS=142.63µM).
