254 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 40 i• 20 z o N 10 lb •o •o 4'0 CONCENTRATION OF BERGAMOT OIL ml/100 ml Figure 3. The effect of increasing concentrations of bergamot oil (Coty) on the diameter of the killing zone of the yeast, presented as the mean + S.E.M. A sharp increase in the zone diameter is noted with the smaller concentrations, and a levelling-off of the response with the higher concentrations. The curve with the inter- rupted lines shows the relationship of the diameters of killing zones produced by known concentrations of pure 5-MOP (shown in Figure 4) to the concentrations of bergamot oil calcalulated from these concentra- tions, assuming the 5-MOP content of bergamot oil to be 0.27 g/100 ml tained (Figure 3). The killing zones obtained with the calculated concentrations were, however, slightly larger than those produced by known concentrations of bergamot oil. Dose-Response Curves.' 8-MOP. The minimal effective concentration of 8-MOP to produce killing of the yeast was 0.0025%, concentrations of 0.00025, 0.0005 and 0.001% being ineffective. Higher concentrations were much less effective than similar concentrations of 5-MOP (Figure 4). Furthermore, the dose-response curve did not show a steep rise with the smaller concentrations as it did with 5-MOP. The results of the turbidimetric test are shown in Table III. Marked inhibition of yeast growth was Table III The Optical Density at 600 nm of Yeast Growth in Sabouraud's Liquid Medium 24 hr After Incubation with 0.1 ml of 0.005% Ethanolic Solutions of 5-MOP and 8-MOP. The Values in the Irradiated Petri Dishes Differ Significantly With a p Value of 0.001 Using Student's "t" Test Irradiated Control 5-MOP 8-MOP 5-MOP 8-MOP OPTICAL Mean 0.114 0.282 0.830 0.860 DEN S ITY S.E.M. 0.004 0.004 0.011 0.006

QUANTITATIVE ANALYSIS OF BERGAPTEN 255 o .6• .o• .o• .6, j CONCENTRATION gm•o • 5-- MOP •l 8- MOP - Figure 4. The effect of increasing concentrations of 5-MOP and 8-MOP on the diameter of the killing zones of the yeast (Mean _+ S.E.M.) 5-MOP is noted to be more photoactive than 8-MOP and its dose- response curve is similar to that of bergamot oil .i '""'" i :5 • • " • -- • .- = . . _.• Figure 5. The results of the phototoxic effects of the bergapten TLC fraction of 0.25, 0.5 and 1% bergamot oil and Yves Saint Laurent toilet water