Inclusion Process And Mechanism Of Salicylic Acid And Its Inclusive Performance

Salicylic acid (abbreviated as SA), known as ortho-hydroxybenzoic acid or2-hydroxybenzoic acid, has a variety of pharmacological activities. It has been widely applied in medicine for it has bactericidal anti-corrosion, anti-inflammatory, anti-rheumatic effects. However, because of strong irritation and poor solubility in water, its application has been relatively limited. As a result, it is a valuable challenge to find an appropriate way to mask its ill smell and taste and to improve its solubility in aqueous solution. Microcapsules are tiny units consisting of acoating or shell material (mostly organic polymers) with an empty volume inside. Microcapsules can incorporate anactive core with different structures, and are used in various commercial products. In this paper, SA microcapsules were systematically investigated.Firstly, P-cyclodextrin (β-CD)/SA inclusion complex was prepared via. co-precipitation. β-CD could form1:1inclusion complex with SA in aqueous solution using ethanol as co-solvent. FTIR, UV-Vis,’H-NMR and2D ROESY have been utilized to analyze the inclusion complex. The equilibrium constant for inclusion (Ka) is928M-1. TGA results indicated that the thermal stability of SA was improved after inclusion with (3-CD. In addition, the structure of the proposed inclusion compound was optimized with PM3and the two-layered hybrid ONIOM method, ONIOM (B3LYP/6-31G:PM3). The free radical-scavenging performance of the inclusion complex was investigated with the stable free radical2,2-diphenyl-l-picrylhydrazyl (DPPH). The improved antioxidant activity is attributed to that the complex could break intramolecular hydrogen bond of SA, thus efficiently eliminate DPPH radicals.Secondly, Chito-oligosaccharide (COS)/SA microcapsules were prepared using a spray-drying technique. Work operating conditions were optimized and set at: diameter of atomizer nipple (0.5mm).2%concentration of COS, COS:SA (1:0.5, m/m). interpump speed6.6ml·min-1. inter air temperature170C, the loading capacity and inclusion ratio were19.1%and21.5%. respectively. Size distribution showed that the microcapsules were in the spherical form mostly in the size range of3-20μm. FTIR. SEM and optical microscopy were utilized to analyze the presence and morphological structure of microcapsules. Controlled release performance of COS/SA microcapsules was analyzed using the dialysis bag methodin vitro dissolution. The results showed that therelease amount of the COS/SA microcapsule were about50%of the pure salicylic acid in6h. Antibacterial properties and minimum inhibitory concentration (MIC) of salicylic acid and its microcapsules were investigated on three kinds of pathogenic bacteria of acne (Staphylococcus aureus, Staphylococcus epidermidis, P.acnes) using disk diffusion method. A cream mostly composed with the COS/SA microcapsules and TTO was prepared and tested for the antimicrobial activity. The results indicated that the cream has significant antimicrobial activity on the three kinds of pathogenic bacteria of acne.In brief, SA microcapsules with higher thermal stability, weak irritation, enhanced solubility and prolonged shelf-life were achieved for SA. Salicylic acid is widelyused asdrug. Therefore, SA microcapsules can be quite applicable in pharmaceutical industry, cosmetics industry, etc. Our study shows that the SA microcapsules would be very effective for achieving weak irritation, enhanced solubility, long-term shelf-life and high temperature stability. Our results should be of interestto food, biomedical, textile and personal care industries, since SA microcapsules may have practical applications depending on the type the functional components used such as flavours, antimicrobials, antioxidants, drugs, and bioactive agents, etc.