Traditional Decoction and PUAE Aqueous Extracts of Pomegranate Peels as Potential Low-Cost Anti-Tyrosinase Ingredients

Featured Application The recycling of the external peels of pomegranate represents an important goal for pomegranate juice manufacturers, since their disposal is expensive and not eco-friendly. Traditional decoction and an innovative ultrasound-assisted method of extraction of pomegranate peels using just water have both led to obtaining aqueous extracts rich in polyphenolic compounds and endowed with anti-tyrosinase activity. Although these aqueous extracts may require a further formulation step for preservation, these findings suggest the possibility of using them as low-cost lightening and/or anti-browning agents, even extemporarily. Abstract The aim of the study is to evaluate the anti-tyrosinase activity of different aqueous extracts obtained from pomegranate juice processing by-products. External pomegranate peels of two certified cultivars (Akko and Wonderful), were extracted using only water as the extraction solvent. A traditional decoction and a pulsed ultrasound-assisted extraction (PUAE), both 10 min long, were performed and compared. All the aqueous extracts proved to be rich in bioactive compounds. In particular, the total phenolic content (TPC) ranged from 148 to 237 mg gallic acid equivalent (GAE)/g of dried peels (DW), the radical-scavenging ability (RSA) ranged from 307 to 472 mg ascorbic acid equivalent (AAE)/g DW, the free ellagic acid content (EA) ranged from 49 to 94 mu g/mL, and the ellagitannins (ETs) ranged from 242 to 340 mu g/mL. For both cultivars, PUAE extracts had higher ET content and a lower EC50, while the decoctions had slightly higher TPC, RSA, and free EA amounts. Principal component analysis (PCA) highlighted the direct correlation between the ET content and the tyrosinase enzyme inhibition (lower values of EC50). These findings suggest the potential use of both these natural extracts as low-cost lightening and/or anti-browning ingredients exploitable in several formulations (e.g., cosmetics) or extemporarily usable.