The active extract of the bark, called salicin, after the Latin name for the white willow. It is derived from the metabolism of salicin. In addition to being an important active metabolite of aspirin (acetylsalicylic acid), which acts in part as a prodrug to salicylic acid, it is probably best known for its use in anti-acne treatments. salicylic acid is used as a food preservative and as bactericidal and antiseptic.