EFFECT OF CYCLOHEXANE AND BENZENE DIESTER ON MELANOGENESIS 181 The results of cytotoxicity tests on octanoyl and 2-ethylhexanoyl—conducted to identify the impact of the structural isomer of the side chain on cytotoxicity—indicate that the levels of cytotoxicity were lower in the branch type than in the linear type across all derivatives except the 1,2-cyclohexane diester derivatives. When the side chain was the same yet the location of diesters (i.e., 1,2-, 1,3-, 1,4-) varied, the 1,3-diester derivatives demonstrated a lower level of cytotoxicity than the 1,2-diester and 1,4-diester derivatives. Table II Viabilitya of Cyclohexane Diester Derivatives (1a–1o) and Benzene Diester Derivatives (2a–2o) on B16F10 Cells Compounds Viability (%) 25 μM 50 μM 125 μM 250 μM 500 μM 1a 100.0 ± 1.4 96.9 ± 1.9 89.3 ± 1.5 84.2 ± 1.8 70.8 ± 2.1 1b 94.8 ± 1.5 93.0 ± 2.5 86.5 ± 1.8 73.1 ± 1.9 65.0 ± 2.3 1c 100.0 ± 1.8 95.3 ± 1.4 79.6 ± 1.9 66.8 ± 2.5 54.7 ± 1.8 1d 100.0 ± 2.6 94.3 ± 1.6 77.9 ± 0.6 54.5 ± 2.3 40.7 ± 1.8 1e 98.9 ± 1.7 90.7 ± 1.8 73.8 ± 2.6 58.4 ± 2.3 40.1 ± 2.8 1f 100.0 ± 0.4 100.0 ± 3.1 100.0 ± 3.3 94.1 ± 2.2 68.1 ± 3.2 1g 100.0 ± 2.7 100.0 ± 2.4 100.0 ± 1.3 96.9 ± 1.0 74.1 ± 2.7 1h 100.0 ± 2.5 98.1 ± 2.4 91.8 ± 1.4 72.7 ± 3.1 41.0 ± 2.3 1i 100.0 ± 2.1 100.0 ± 2.6 99.3 ± 2.9 99.2 ± 1.6 98.5 ± 1.3 1j 100.0 ± 2.2 100.0 ± 1.1 100.0 ± 1.9 96.1 ± 2.4 96.0 ± 1.8 1k 75.2 ± 1.5 62.1 ± 2.7 57.9 ± 1.6 50.7 ± 1.6 40.2 ± 1.4 1l 91.9 ± 2.1 89.7 ± 0.2 88.8 ± 0.8 85.7 ± 0.9 61.8 ± 1.3 1m 100.0 ± 2.0 100.0 ± 3.1 89.5 ± 2.7 89.5 ± 2.3 79.1 ± 2.4 1n 99.3 ± 3.5 96.8 ± 2.1 95.0 ± 2.2 89.9 ± 3.7 82.4 ± 2.2 1o 93.0 ± 1.2 90.6 ± 0.4 90.0 ± 1.3 87.4 ± 1.7 84.9 ± 1.9 2a 75.6 ± 1.9 64.9 ± 2.4 59.6 ± 3.4 44.3 ± 2.6 7.6 ± 1.5 2b 75.8 ± 0.5 73.1 ± 2.5 59.3 ± 2.8 46.6 ± 2.6 40.2 ± 2.8 2c 93.1 ± 3.0 77.8 ± 3.0 72.3 ± 2.3 61.2 ± 1.8 57.9 ± 2.2 2d 61.3 ± 1.6 58.6 ± 1.3 56.0 ± 2.3 53.0 ± 0.7 48.0 ± 2.7 2e 100.0 ± 2.1 100.0 ± 2.2 100.0 ± 2.5 100.0 ± 2.3 74.3 ± 1.6 2f 92.7 ± 1.0 88.3 ± 1.6 76.8 ± 2.2 65.9 ± 1.8 59.8 ± 2.5 2g 100.0 ± 0.4 98.5 ± 0.6 86.5 ± 1.0 80.6 ± 2.3 62.5 ± 2.3 2h 100.0 ± 2.7 97.4 ± 1.2 94.1 ± 2.1 78.4 ± 2.7 66.9 ± 0.4 2i 100.0 ± 1.4 100.0 ± 2.0 100.0 ± 1.8 99.7 ± 2.4 98.9 ± 2.9 2j 100.0 ± 2.0 100.0 ± 2.1 100.0 ± 2.6 97.7 ± 2.3 94.2 ± 1.2 2k 66.3 ± 1.4 57.5 ± 1.8 34.4 ± 2.3 3.3 ± 0.3 3.2 ± 0.1 2l 49.4 ± 2.6 47.1 ± 2.9 36.2 ± 1.4 21.6 ± 1.5 7.5 ± 0.1 2m 41.5 ± 0.9 33.9 ± 2.1 23.4 ± 0.8 19.8 ± 1.1 18.4 ± 1.1 2n 80.5 ±1.3 78.4 ± 1.4 77.1 ± 0.5 76.4 ± 1.0 74.2 ± 1.5 2o 69.2 ± 1.5 59.3 ± 3.6 58.6 ± 0.5 56.6 ± 1.9 52.9 ± 0.9 a Values are means of three experiments.

JOURNAL OF COSMETIC SCIENCE 182 MELANIN SYNTHESIS INHIBITORY EFFECTS OF CYCLOHEXANE DIESTER DERIVATIVES (1A–1O) AND BENZENE DIESTER DERIVATIVES (2A–2O) ON B16F10 CELLS Table III indicates the melanin synthesis inhibitory activities of cyclohexane diester derivatives (1a–1o) and benzene diester derivatives (2a–2o) in B16F10 cells. As illus- trated in the table, the cyclohexane diester derivatives of 1i and 1m and the benzene diester derivative of 2j had 479.3 ± 1.3 μM, 497.9 ± 3.8 μM, and 474.7 ± 9.4 μM as IC50 values at the concentration level involving no cytotoxicity. Against this backdrop, Table III Melanin Inhibitory Activitya of Cyclohexane Diester Derivatives (1a–1o) and Benzene Diester Derivatives (2a–2o) on B16F10 Cells Compounds Melanin content % Inhibition at 25 μM IC50 (μM) 1a 0 NDb 1b 3.47 ± 0.6 ND 1c 0.42 ± 0.2 ND 1d 0.76 ± 0.7 ND 1e 9.05 ± 1.8 ND 1f 0 ND 1g 0 ND 1h 1.5 ± 1.3 ND 1i 8.8 ± 1.5 479.3 ± 1.3 1j 0 ND 1k 13.4 ± 1.6 ND 1l 0 ND 1m 4.1 ± 0.3 497.9 ± 3.8 1n 0 ND 1o 0 ND 2a ND ND 2b ND ND 2c 0 ND 2d ND ND 2e 2.8 ± 0.2 ND 2f 0 ND 2g 1.5 ± 1.2 ND 2h 0 ND 2i 1.1 ± 0.5 ND 2j 2.3 ± 1.9 474.7 ± 9.4 2k 5.62 ± 0.5 ND 2l ND ND 2m ND ND 2n 20.7 ± 4.3 ND 2o ND ND a Values are means of three experiments. b Not done.