Physicochemical and microbiological properties as well as stability of ointments containing aloe extract (Aloe arborescens Mill.) or aloe extract associated to neomycin sulphate.

The aim of the study was to work out methods of quality assessment of ointments containing dry extract from fresh leaves of Aloe arborescens Mill. (Lilliaceae) and also of ointments containing both of dry extract and neomycin sulphate. The stability of the ointments, stored at 20 degrees C, was studied and the following criteria were considered: chromatographic analysis (TLC), pH of the ointments, the content of the substances in the dry extract converted to aloenin, the content of aloenin and aloin, anti-microbial activity of neomycin in the ointments, the size of the particles of the dry extract and of neomycin sulphate in the ointment suspension and the sterility of the ointments. After two years of storage at 20 degrees C, the ointments prepared with the anhydrous lipophilic base, did not change their physicochemical characteristics and neomycin in those ointments retained almost 100% of starting anti-microbial activity. Water or propylene glycol significantly decreased the stability of the biologically active substances of the dry extract in the ointments. Besides, in the ointments containing the dry extract and neomycin sulphate, the presence of water or propylene glycol induced degradation of the biologically active substances of the dry extract and a decrease in the anti-microbial activity of neomycin in the ointments. Considering the physicochemical and microbiological stability, the most advisable base for the ointments with aloe and neomycin sulphate was composed of white vaseline, liquid paraffin, solid paraffin, cholesterol.