Comprehensive Study of Anti-UVC Activity and Cytotoxicity of Hot-water Soluble Herb Extracts

Abstract

Background/Aim: COVID-19 pandemic caused the rapid dissemination of ultraviolet C (UVC) sterilization apparatuses. Prolonged exposure to UVC, however, may exert harmful effects on the human body. The aim of the present study was to comprehensively investigate the anti-UVC activity of a total of 108 hot-water soluble herb extracts, using human dermal fibroblast and melanoma cell lines, for the future development of skin care products. Materials and Methods: Exposure time to UVC was set to 3 min, and cell viability was determined using the MTT assay. Anti-UVC activity was determined using the selective index (SI), a ratio of 50% cytotoxic concentration for unirradiated cells to 50% effective concentration that restored half of the UVC-induced decrease of viability. Results: Dermal fibroblasts at any population doubling level were more resistant to UVC irradiation than melanoma cells. Both 49 herb extracts recommended by Japan Medical Herb Association (JAMHA) and 59 additional herb extracts showed comparable anti-UVC activity. SI values of selected herbs (Butterbur, Cloves, Curry Tree, Evening Primrose, Rooibos, Stevia, Willow) were several-fold lower than those of vitamin C and vanillin. Their potent anti-UVC activity was maintained for at least 6 h post irradiation, but declined thereafter to the basal level, possibly due to cytotoxic ingredients. Conclusion: UVC sensitivity may be related to the growth potential of target cells. Removal of cytotoxic ingredients of herb extracts may further potentiate and prolong their anti-UVC activity.SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection caused the coronavirus disease of 2019 (COVID-19) pandemic, accompanied by serious morbidity and mortality (1). This triggered the rapid dissemination of various types of ultraviolet C (UVC) sterilization apparatuses in hospital emergency department waiting rooms, clinics, nursing homes, prison common areas, public libraries (providing the sterilization box for cleaning books), schools, restaurants, and bedrooms (2). While UVC has strong bactericidal (3) and virucidal (4) activity, the prolonged exposure to UVC may have harmful effects on the human body, causing various diseases such as skin cancer (5) and cataracts (6). Therefore, the search for nontoxic UVC protective substances is crucial. Sakagami et al. recently reported that (i) human normal cells (gingival, periodontal, and dermal fibroblasts and pulp cells] are generally resistant to UVC irradiation, as compared with human cancer cell lines (oral squamous cell carcinoma, lung cancer, glioblastoma, leukemia, and melanoma) (7); and that (ii) 1540

UVC-Protective Activity of Lemongrass Among 12 Fat-soluble Herbal Extracts: Rapid Decay Due to Cytotoxicity

“…Human dermal fibroblasts adult (HDFa) from adult skin (C0135C; Thermo Fisher Scientific, Waltham, MA, USA) and human melanoma cells (COLO679) (R21-0267; Riken Cell Bank, Tsukuba, Japan) were cultured at 37˚C in regular culture medium [Dulbecco's modified Eagle's medium supplemented with 10% heat-inactivated (56˚C for 30 min) fetal bovine serum, 100 U/ml penicillin G, and 100 μg/ml streptomycin sulfate] in a humidified atmosphere with 5% CO 2 (7). HDFa cells were harvested by in vivo 37: 2464-2472 (2023) 2465 (12), were used in this study. COLO679 cells were similarly detached by trypsinization and seeded at a 1:8 ratio to allow their logarithmic growth, when they became near-confluent.…”

“…The 96-microwell plates on which cells were growing were placed at 555 mm from the center of a UVC lamp (254 nm, germicidal lamp GL15; Toshiba Co. Ltd., Tokyo, Japan) set within an MCV-B131F BioClean Bench (Panasonic Healthcare Co., Ltd., Tokyo, Japan) (Figure 1A). The radiation intensity at the center below the UVC lamp as measured by a UVC radiometer (Gigahertz Optik GmbH, Tuerkenfeld, Germany) was 1.193 W/m 2 (12). In experiments, cells were irradiated for 3 min.…”

“…Cells (3×10 4 /ml, 0.1 ml) were inoculated in the inner 60 wells of a 96-microwell plate. The surrounding 36 exterior wells were filled with 150 μl of sterile distilled water to minimize the evaporation of water from the culture medium (Figure 1A), as described previously (12). Cells were incubated for 48 h to achieve complete attachment to the plate.…”

“…Izawa et al recently investigated the anti-UVC activity of a total of 108 hot-water-soluble herbal extracts (including 59 herbal extracts recommended by the Japan Medical Herb Association) against human dermal fibroblast (HDFa) and melanoma (COLO679) cell lines. Selected herbs (butterbur, clove, curry tree, evening primrose, rooibos, stevia and willow) showed several-fold lower UVC protection compared with vitamin C and vanillin (12). Their potent UVC-protective activity was maintained for at least 6 h post irradiation, but declined thereafter to a basal level, possibly due to their cytotoxicity or the coexistence of cytotoxic components (12).…”

“…Selected herbs (butterbur, clove, curry tree, evening primrose, rooibos, stevia and willow) showed several-fold lower UVC protection compared with vitamin C and vanillin (12). Their potent UVC-protective activity was maintained for at least 6 h post irradiation, but declined thereafter to a basal level, possibly due to their cytotoxicity or the coexistence of cytotoxic components (12). It is thus necessary to investigate not only the UVC-protective activity of candidate substances but also their toxicity.…”