Background: UV-B irradiation is the major causative factor in photoaging. Photoaging increases MMP-1 significantly and cause damage to collagen by forming ROS. The monounsaturated free fatty acids and antioxidant compounds in Tamanu oil have been studied to inhibit the emergence of MMP-1 and maintain collagen amount. The study aimed to investigate topical Tamanu oil in inhibiting MMP-1 expressions and collagen decrease in male Wistar rats’ skin exposed to UV-B. Methods: A randomized post-test-only control group design was performed on 36 male Wistar rats, aged 2-3 months old with 180-220 grams body weight. They were assigned to two groups: the placebo group and the Tamanu oil group. Both groups were given the same amount of UV-B exposure for four weeks totalling in 840 mJ/cm2 of dosage radiation. Their dermis was examined for MMP-1 using Immunohistochemistry and collagen amount using Picro Sirius Red staining. Results: A comparative analysis was done to show the difference between groups. The mean expression of MMP-1 in the control group was 34,03±2.97 cell/HPF and the Tamanu oil group was lower at 22.73±2.68 cell/HPF. The mean amount of collagen dermis in the control group was 38.90±11.64 % and the Tamanu oil group was higher at 65.66±8.13 %. A significant difference was shown in the two groups (p Conclusion: Topical Tamanu oil has proven to hinder the increase of MMP-1 expressions and collagen amount in male Wistar rats’ skin exposed to UV-B.

Oil from the nuts of Calophyllum inophyllum, locally called "Tamanu oil" in French Polynesia, was traditionally used for wound healing and to cure various skin problems and ailments. The skin-active effect of "Tamanu oil emulsion" was investigated on human skin cells (keratinocytes and dermal fibroblasts) and showed cell proliferation, glycosaminoglycan and collagen production, and wound healing activity. Transcriptomic analysis of the treated cells revealed gene expression modulation including genes involved in the metabolic process implied in O-glycan biosynthesis, cell adhesion, and cell proliferation. The presence of neoflavonoids as bioactive constituents in Tamanu oil emulsion may contribute to these biological activities. Altogether, consistent data related to targeted histological and cellular functions brought new highlights on the mechanisms involved in these biological processes induced by Tamanu oil effects in skin cells.