Skin penetration of terpenes from essential oils and topical vehicles.
The purpose of this study was to evaluate the in vitro cutaneous penetration of five terpenes--linalool, linalyl acetate, terpinen-4-ol, citronellol and alpha-pinene--applied in pure essential oils or in dermatological formulations (o/w emulsion, oily solution or hydrogel) containing 0.75 % w/w of the essential oils. Different skin absorption was observed depending on the type of the vehicle and terpenes' log P values. Cutaneous accumulation of terpenes is several times higher when they are applied in pure essential oils than in topical vehicles. Penetration of terpinen-4-ol to the skin was better from an oily solution (approximately 90 microg/cm (2)) than from an emulsion (60 microg/cm (2)). No penetration of linalyl acetate from topical vehicles into viable skin was observed, but also for this terpene penetration to the upper layers of the stratum corneum was 2-times higher when an oily solution was used. In contrast, the cutaneous absorption of linalool was the same from both vehicles (50-60 microg/cm (2)). The skin penetration of alpha-pinene was not traceable when it was applied in an oily solution. Only a small amount (approximately 5 microg/cm (2)) of this terpene was determined in viable skin after application as a hydrogel. Citronellol applied in a hydrogel penetrated into all skin layers in a total amount of 25 microg/cm (2), while no penetration into viable skin layers after application of an oily solution was noted. Only citronellol permeated into the acceptor medium.
Cal
Krzysztof
K
Department of Pharmaceutical Technology, Medical University of Gdansk, Gdansk, Poland. kcal@wp.pl
D000080462:Acyclic Monoterpenes; D000279:Administration, Cutaneous; D000328:Adult; D000081008:Bicyclic Monoterpenes; D005260:Female; D006801:Humans; D007641:Keratolytic Agents / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use; D008875:Middle Aged; D039821:Monoterpenes / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use; D008517:Phytotherapy; D010938:Plant Oils / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use; D010946:Plants, Medicinal; D012867:Skin / Q000378:metabolism; D012869:Skin Absorption / Q000187:drug effects*; D013729:Terpenes / Q000494:pharmacology
D000080462:Acyclic Monoterpenes; D000081008:Bicyclic Monoterpenes; D007641:Keratolytic Agents; D039821:Monoterpenes; D010938:Plant Oils; D013729:Terpenes; C034019:terpinenol-4; C074463:linalyl acetate; C018584:linalool; C005451:alpha-pinene; C007078:citronellol