Anti-Photoaging Effects of Kaempferia galanga Extract: From Cell-Based Studies to Microemulsion Development

Ozone layer depletion exacerbates UV-induced skin damage, including oxidative stress and DNA lesions, thereby increasing the risk of photoaging and malignant transformation. Natural extracts have gained increasing attention as a photoprotective ingredient in cosmeceutical products. Kaempferia galanga, a species in the Zingiberaceae family traditionally used for skin-related treatment and listed in the CosIng database, exhibits multiple biologically relevant properties; however, its anti-photoaging and anti-photo-senescence effects in human dermal fibroblasts remain unexplored. This study investigated the in vitro photoprotective effects of K. galanga extract against UVB-induced photoaging and cellular senescence in human dermal fibroblasts. The ethanolic extract of K. galanga rhizomes (EKGRs) contained ethyl p-methoxycinnamate (EPMC) as a major constituent (33.7 ± 3.7% (w/w) of the crude extract), identified by HPLC-UV. Additionally, EKGR exhibited significant protective effects in UVB-irradiated fibroblasts. EKGR showed no cytotoxicity at concentrations up to 50.0 µg/mL, as determined by the MTT assay. EKGR pretreatment significantly reduced UVB-induced cellular senescence in human dermal fibroblasts compared with UVB-exposed cells (22.2 ± 2.7% vs. 36.7 ± 8.0%). Furthermore, pretreatment with EKGR prior to UVB exposure resulted in a significant increase in pro-collagen type I production (37,075.1 ± 7532.2 pg/mL) and a concomitant decrease in MMP-1 secretion (25,754.1 ± 4042.0 pg/mL) relative to UVB-exposed cells (26,845.8 ± 1454.6 and 39,910.8 ± 6035.1 pg/mL, respectively). To demonstrate formulation feasibility, EKGR was incorporated into an oil-in-water microemulsion, which exhibited concentration-dependent SPF enhancement. Collectively, these findings demonstrate the photoprotective efficacy of EPMC-rich EKGR and highlight its potential as a cosmeceutical ingredient for mitigating UVB-induced photo-senescence and skin aging, with an additional SPF boosting effect. To our knowledge, this study provides the first evidence of EKGR-mediated protection against UVB-induced cellular senescence in human dermal fibroblasts.