Background: Sahasthara (SHT) is a Thai traditional remedy for relieving muscles and bones pain. Presently, topical dosage forms of SHT extract (SHTE) are used instead of oral dosage forms of SHT to avoid gastrointestinal side effects such as nausea and vomiting. However, topical products of SHTE have not been accepted by some patients because of unpleasant odor and color of SHTE used in formulations. Therefore, to increase patient’s acceptance, the unpleasant odor and color of the crude extract should be removed before use as an active ingredient in the products.
Objective: To determine an optimum dose of activated carbon for improving physical appearance of SHTE and to evaluate its anti inflammatory activity, chance of being skin irritant and physicochemical properties of SHTE after being treated with activated carbon.
Material and Method: SHTE was treated with various amounts of activated carbon and investigated for its inhibitory activity on nitric oxide production in RAW 264.7 cells and potential for being a skin irritant by MTT assay on skin fibroblasts. Measurement of lightness values, piperine contents by HPLC and pH values of treated SHTE were also performed.
Results: SHTE treated with 0%, 10% and 20% activated carbon showed an anti-inflammatory activity with IC50 values of 4.15+0.58, 7.27+0.53, 7.92+0.23 μg/mL, respectively. None of them was toxic to skin fibroblasts. Lightness of SHTE and piperine contents of such extracts decreased with increase in doses of activated carbon. On the other hand, the higher amount of activated carbon used, the higher is the pH value.
Conclusion: SHTE treated with 20 % w/w activated carbon resulted in better physical appearance of SHTE than that of either untreated- or 10% activated carbon-treated SHTE. Yet, it retained an anti-inflammatory activity with no potential for being a skin irritant. Therefore, treating SHTE with 20 % w/w activated carbon can be further used for preparation of SHT topical formulations.

Keywords: Activated carbon, Anti-inflammatory activity, Physicochemical properties, Sahasthara remedy, Thai traditional
medicine