INFLUENCE OF DIFFERENT PENETRATION ENHANCERS ON IN-VITRO SKIN PERMEATION AND IN-VIVO PHOTOPROTECTIVE EFFECT OF FLAVONOIDS

In the present study the permeation of two flavonoids (naringenin and hesperetin) through excised human skin mounted in Franz diffusion cell s and its possible optimization following skin pretreatment with two p enetration enhancers (D-limonene and lecithin) were determined. Hesper etin and naringenin were able to permeate through excised human skin; moreover, skin pretreatment with D-lmonene and lecithin increased, to different degrees, their cutaneous permeation. On the basis of finding s obtained in these in vitro experiments, we designed a schedule for a series of in vivo experiments, in which the protective effect of topi cally applied naringenin and hesperetin against UV-B-induced skin dama ge was assessed monitoring the extent of erythema in human volunteers by means of reflectance spectrophotometry. Hesperetin and naringenin f rom formulations containing the flavonoid alone were completely ineffe ctive in decreasing UV-B-induced erythema. Furthermore, both D-limonen e and lecithin have enhanced, to a significant extent, the photoprotec tive activity of naringenin and hesperetin. Taken together. these data :demonstrate that hesperetin and naringenin may be successfully emplo yed as topical photoprotective agents. However their topical activity needs to be optimized by using suitable penetration enhancers. (C) 199 8 Elsevier Science B.V. All rights reserved.