1,6-Digalloyl glucose in <i>Emblica officinalis</i> increases the proliferation of human keratinocytes and fibroblasts with upregulated expression of periostin

Keratinocytes and fibroblasts are the major cell types in the epidermis and the dermis, respectively. Since both cells play important roles in wound healing, compounds that regulate their proliferation are expected to be beneficial to epidermal health. We have previously shown that the extract of Emblica officinalis, which is a well-known herb in Ayurvedic traditional medicine, increases the proliferation of keratinocytes. Here, we purified a compound that increased cell proliferation from E. officinalis extract. Through liquid chromatography electrospray ionization tandem mass spectrometry and nuclear magnetic resonance (NMR) techniques, the compound was determined to be 1,6-digalloyl glucose. Consistent with this, tannic acid, a type of polygalloyl glucose, also increased cell proliferation. We further found that E. officinalis extract increased the proliferation of fibroblasts as well and showed that it increased cell proliferation at least partly through upregulating the expression of periostin. These findings revealed the mechanism by which E. officinalis extract regulates cell proliferation.