Development of a New Delivery System Containing Lapachol for Topical Application

Introduction: Natural products are secondary metabolites from plants and other living organisms, which have high therapeutic potential and are therefore of great interest to the pharmaceutical industry. Lapachol is a naftoquinone extracted from the bark of trees of the genus Tabebuia sp, with a wide therapeutic range. This natural product has been already used for cancer treatment, but its toxicity when administered orally lead to the discontinuation of the use. However, this molecule present low toxicity for the cutaneous application and the high bactericidal properties. In this way, these characteristics make lapachol an alternative compound in the development of new medicines for the treatment of skin infections caused by multiresistant bacteria, as well as promoting the use of waste from the timber industry that uses or processes sustainable. Objectives: The aim of the present work was to extract, purify and characterize lapachol from Ipê sawdust and incorporate it into a topical pharmaceutical formulation to evaluate its stability and antimicrobial activity. Methodology: To obtain lapachol we used the methodology of Barbosa and Diniz Neto (2013), which used sawdust of Ipê and HCl 6M and 1% Na2CO3 reagents to induce an acid-base reaction. The product obtained was recrystallized, using heated ethanol and activated carbon. Subsequently, classical column chromatography was performed to separate the compounds. For structural elucidation of lapachol, we used gas chromatography coupled to mass spectrometry (GC-MS). In the development of the formulation, the methodology of Nunes et al (2016) was employed, where 100 g of a 5% lapachol controlled release system were prepared, containing also murumuru butter (Astrocaryum murumuru) and Procetil® surfactant. For microbiological activity, triplicate diffusion methods and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were used for inhibited microorganisms, as established by the M7-A6 standard of the Manual Clinical and Laboratory Standards Institute ( CLSI, 2006), using the suspensions of Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa corrected on the MacFarland 0.5 scale. Results and Discussion: After the extraction and purification processes of lapachol, 986.7 mg of lapachol were obtained, and the yield was 0.07% from the Ipê sawdust. This product showed retention time of 46.32 min in the GC-MS analysis which according to the NIST Mass Spectrum Library corresponds to the desired naphthoquinone. The material was 86.7% pure, by the CG-MS analysis. The formulation obtained using murumuru butter (Astrocaryum murumuru), water and surfactant formed an ideal controlled release system for lapachol incorporation. Preliminary stability analyzes are underway. In the microbiological evaluation of the formulation it was shown it is effectiveness against S. aureus and S. epidermidis strains, evidenced by the formation of inhibition halos of 14 and 18 mm, respectively. However, it did not inhibit P. aeruginosa growth. In MIC determination, lapachol inhibited bacterial strains at a minimum concentration of 500 µg / mL. In S. epidermidis MBC lapachol was bactericidal at 1000 µg/mL and bacteriostatic at 500 µg / mL. For S. aureus the same concentrations were tested and the product was bacteriostatic.
Final considerations: The present work demonstrated that obtaining lapachol by sustainable processes using sawdust is an alternative to traditional methods. Thus, the combination of this feature with its antibacterial properties has led to the development of a new promising product for the treatment of skin infections.