In vivo and in vitro percutaneous absorption of cancer preventive flavonoid apigenin in different vehicles in mouse skin

Purpose. In vivo and in vitro percutaneous absorption of apigenin was investigated in three vehicles previously used in cancer prevention studies to determine the drug delivery properties for optimal chemopreventive activity. Methods. In vivo percutaneous absorption of apigenin on SENCAR mice was studied with DMSO and acetone/DMSO (A/D, 4:1) vehicle. In vitro percutaneous absorption studies used whole mouse skin, without subcutaneous fat, mounted on Franz diffusion cells with 37 degrees C Dulbecco's phosphate-buffered saline as the receptor fluid. The skin was treated with [G-H-3]-apigenin in DMSO, A/D (4:1), or propylene glycoy/DMSO (PG/D, 4:1). Results. Apigenin uptake by epidermal cells and distribution in epidermis following in vivo topical treatment in two vehicles was in the order of A/D > DMSO, while apigenin distribution in dermis and subcutaneous fat was not different between DMSO and A/D. Total apigenin absorption in mouse skin in vitro was in the order of A/D > DMSO > PG/D. However, apigenin sub-tissue distribution within epidermis determined by tape-stripping and by determination of apigenin in dermal and epidermal tissue indicated that DMSO delivered more apigenin into viable epidermis than A/D while A/D deposited more apigenin in the stratum corneum. Apigenin absorption in mouse skin with DMSO or A/D showed saturation kinetics while apigenin in PG/D showed very low absorption initially and non-saturated absorption in a period of 6 hr. HPLC-scintillation profiles of in vitro samples showed no evidence of apigenin metabolism in mouse skin. Conclusions. Delivering apigenin into viable epidermis appears to be a necessary property for an apigenin formulation to be effective in skin cancer prevention.