Water-retentive and anti-inflammatory properties of organic and inorganic substances from Korean sea mud

Sea mud has been popularly used as an effective base in cosmetic preparations although its biologically-active materials and mechanisms on skin have not yet been fully determined. We isolated humic substances as the major organic substance of the sea mud from a tidal flat in Korea, and investigated their water-retentive properties. Among the three isolated humic substances, humic acid (HA) showed the highest water retentive property (∼ 50 % mass increase from water uptake). Based on the observations that mud pack therapy has been traditionally used to soothe UV-irradiated skin, we examined the antiinflammatory property of the sea mud on UVB-irradiated human keratinocytes (HaCaT cells) by measuring PGE₂ levels produced by keratinocytes in the presence of either the total water or methanol extracts of the mud. The water extract showed higher inhibition of PGE₂ production from HaCaT cells (30 % inhibition) than the methanol extract at 200 ppm (μg/g). We further fractionated the water extract to determine the major components responsible for its anti-inflammatory effect. It was found that the minerals in the mud inhibited PGE₂ production by 83 % at 200 ppm, which is comparable with the inhibitory effect of 1 μM indomethacin. No mud extract showed cytotoxicity at the tested concentrations. The mineral compositions of the mineral extract were determined by ICP-MS, revealing that the sea mud consisted of more than 19 different mineral components, rich in Na⁺, Mg²⁺, and Zn²⁺. These results imply that the anti-inflammatory effect of the sea mud is largely due to the minerals in the mud. Our research suggests the potential use of the organic and inorganic substances from the sea mud in various skin products as safe biological substances for skin protective purposes.