Complex sentence: Acetylcysteine serves as a prodrug to L-cysteine which is a precursor to the biologic antioxidant, glutathione and hence administration of acetylcysteine replenishes glutathione stores.
Split into simpler sentences: Acetylcysteine serves as a prodrug to L-cysteine which is a precursor to the biologic antioxidant, glutathione. Hence administration of acetylcysteine replenishes glutathione stores.