IntroductionKeloids 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 study aim is to evaluate the effects of tagitinin C from Tithonia diversifolia to keloid fibroblasts (KF).MethodsMonolayer 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.ResultsThe 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.ConclusionIt 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.