Introduction: keloids characterized by fibroblast hyperproliferation and depositions of collagen which similar to cancer cells. Tagitinin C is a class of sesquiterpene lactones (SLS) was isolated from the leaves of the moon flower Tithonia diversifolia (Hemsley) A. Gray.The previous studies show that tagitinin C has a cytotoxic effect on selective skin cancer cell. The study aim is to evaluate the effects of tagitinin C from Tithonia diversifolia to keloid fibroblasts (KF).

Methods: monolayer cultures of keloid fibroblast (three passages) were treated with 8 serial concentration of tagitinin C (0.015 to 2) μg/mL during 72 and 120 hours. A positive control using mitomycin C. Cellular viabilities were measured by MTT assay. Collagen depositions were measured by Sirius Red assay for nonsoluble collagen.

Results: the reading of the result was conducted by ELISA reader. Data were analyzed by probit regression with SPSS 19 for Windows. The result showed that tagitinin C can inhibit keloid fibroblasts (KF) viability with IC₅₀ 0.122 μg/mL (incubation 72h) and 0.039 μg/mL (120h), whereas mitomycin C IC₅₀ 0.120 μg/mL (72h) and IC₅₀ of 0.100 μg/mL (120h). At IC₅₀ concentration of tagitinin C on keloid collagen deposition 53.1% (72h) and 44.3% (120h), whereas the IC₅₀ concentration of mitomycin C on keloid collagen deposition 60.4% (72h) and 52.1% (120h). Selectivity index tagitinin C on normal fibroblasts (NF) is 287 for 72h incubation and 791 for 120h incubation.

Conclusion: it can be concluded that the ability of tagitinin C inhibits KF viability and decreasing keloid collagen deposition is consistent with the concentration (concentration-dependent) and incubation time (time-dependent). Tagitinin C has a low toxicity level on NF with high selectivity index.