The inhibitory effect of an extract of Sanguisorba officinalis L. on ultraviolet B-induced pigmentation via the suppression of endothelin-converting enzyme-1 alpha

Endothelin-l (ET-1) has been reported to be expressed in human epidermis at both the gene and protein levels, ET-I plays a pivotal role in ultraviolet B (UVB)-induced pigmentation due to its accentuated secretion after UVB ir radiation and its function as a mitogen and as a melanogen for human melano cytes, We have recently found that endothelin-converting enzyme (ECE)-1 alp ha plays a constitutive role in the secretion of ET-I by human keratinocyte s and that an extract of Sanguisorba officinalis L. inhibits ECE activity i n human endothelial cells, which predominantly express ECE-la. In this repo rt, to clarify the potential use of this botanical extract as a whitening a gent, we examined whether this extract inhibits UVR-induced pigmentation in vivo. When this extract was applied to human keratinocytes after UVB irrad iation, secretion of ET-1 by those cells was reduced, and this was accompan ied by a concomitant increase in the secretion of inactive precursor Rig en dothelin-l, When hairless mice were exposed to UVB light and were treated w ith the extract, it suppressed the induction of ET-1 in the UVB-irradiated epidermis, In the course of UVB-induced pigmentation of brownish guinea pig skin, this extract significantly diminished pigmentation in UVB-exposed ar eas. These findings indicate that ECE-I a in keratinocytes plays a pivotal role in the induction of pigmentation following UVB irradiation and that an extract of S, officinalis, which inhibits ET-1 production in human keratin ocytes, is a good ingredient for a whitening agent.