Bioprospection of photoprotective natural compounds from Persea fulva: a good source of acylated glycosylated flavonoids for application in new sunscreen formulas

Formulations containing natural extracts have garnered attention due to the importance of these compounds in protecting against ultraviolet radiation (UV) due to their antioxidant and UV-absorbing properties, which enhance photoprotection and reduce reliance on synthetic agents. This study developed a photoprotective formulation containing a glycosylated flavonol-rich extract from Persea fulva. The crude extract was incorporated into an emulgel formulation, which demonstrated Sun Protection Factor (SPF) values of up to 48.94 at 20 mg/mL, reaching in vitro SPF values consistent with high protection according to Brazilian guidelines. This formulation remained physicochemically stable for 90 days, maintaining its pH, organoleptic and texture attributes. To identify the active compounds responsible for photoprotection, a bio-guided fractionation approach was applied to the P. fulva crude extract. Accordingly, liquid-liquid partitioning of this extract yielded several fractions, among which the ethyl acetate fraction exhibited the highest SPF (33.08 ± 0.36 at 500 µg/mL), comparable to the commercial UV filter benzophenone. Successive chromatographic fractionations of the ethyl acetate fraction, continuously monitored for SPF, total phenolic content, total flavonoid content and DPPH radical scavenging activity, led to the isolation of tiliroside as the major compound, along with six other minor glycosylated flavonols, whose aglycones were identified as quercetin and kaempferol. These compounds were identified by NMR and LC-MS/MS, respectively. Additionally, theoretical calculations of HOMO-LUMO orbitals performed through in silico studies confirmed the UV-absorbing properties of these flavonoids. These findings indicate that the flavonoids tiliroside and its derivatives found in P. fulva suggest their potential as candidates for the development of photoprotective formulations.