Purpose: Inflammation is a pathophysiological response of living tissues. It is not only a defense mechanism of living tissues but also a part of some diseases, for example, arthritis, dermatitis, autoimmune diseases and cancers. Sahastara (SHT) remedy is a Thai traditional medicine used as an alternative medicine for muscle and bone pain in Thai people. It has been officially listed in the Thai National List of Essential Medicine since 2011. It is composed of fruits of black pepper (Piper nigrum) as a major constituent, and some of long pepper (Piper retrofractum). Therefore, anti-inflammatory activities of SHT remedy mostly come from bioactivities of piperine consisting of these pepper plants. The aims of this study were to determine anti-inflammatory activities of an alcoholic extract of SHT remedy (SHT-E) and to investigate physicochemical properties of a film forming solution (FFS) containing SHT-E (SHT-E FFS) including its anti-inflammatory activities.
Methods: SHT-E was prepared and evaluated for piperine content by high performance liquid chromatography (HPLC) technique. It was investigated its anti-inflammatory activities in RAW 264.7 cells. SHT-E (3%w/w) was added to base FFS (Base FFS) containing a water insoluble polymer, a water soluble polymer and a plasticizer at a weight ratio of 3.25:3.25:0.8, respectively, and hydroalcoholic solution to obtain SHT-E FFS. Physicochemical properties of SHT-E FFS, i.e., pH, rheological properties and surface morphology, mechanical properties and drug release of the film obtained from SHT-E FFS (SHT-E film) were studied. Furthermore, skin toxicity test and in vivo anti-inflammatory test of SHT-E FFS were also performed.
Results: The obtained SHT-E had slightly dark green color, its characteristic odor and clear appearance. The content of piperine in SHT-E was 85.08±1.03 mg/g. IC50 values of SHT-E for inhibition of NO production and inhibition of PGE2 released by RAW264.7 cells were 7.92±0.23 and 13.23±0.23 μg/mL, respectively. The appearance of obtained SHT-E FFS was transparent but it had slightly brown color with slightly characteristic odor and acidic property of SHT-E. Rheogram of SHT-E FFS revealed Newtonian flow behaviors with low viscosity of 0.062±0.004 Pa. SHT-E film had smooth and nonporous surface. Its tensile stress, percentage elongation at break and tack were 0.99±0.09 MPa, 5.33±0.12, 18.05±0.05 gf, respectively. Piperine was released from SHT-E film with a constant rate following a zero order kinetic model. Skin toxicity test showed that SHT-E FFS and SHT-E film were not toxic to skin cells. Furthermore, SHT-E FFS could reduce rat ear edema more than 60% and about 40% after ear edema induction for 1 and 2 hours, respectively.
Conclusion: SHT-E FFS was prepared successfully in this study. It had promising physicochemical properties and was safe for using as topical products. Furthermore, it showed a moderate to high anti-inflammatory activity in reduction of rat ear edema. Therefore, SHT-E FFS had potential for using in further clinical study to investigate its efficacy and safety in patients.