Cytotoxicity, antioxidant, anti-inflammatory, and sun protection potential of spray-dried Punica granatum peel extract

Punica granatum (pomegranate) possesses strong antibacterial, antiviral, antioxidant, and anti-inflammatory activity due to the presence of various organic acids, alkaloids, phenolic acids, tannins, flavonoids, anthocyanins, sugars, fatty acids, and vitamins. Thus, in the present study, spray-dried pomegranate peel extract was examined in terms of its cytotoxicity and antioxidant, anti-inflammatory, and sun protection potential. The extract showed a concentration-dependent effect on keratinocyte viability, producing a decrease in the viability of the HaCaT cells with rising concentrations. While 25 µg/mL did not significantly reduce cell viability (12% reduction), concentrations of 50 and 100 µg/mL showed a more profound effect (23% and 27% reductions, respectively). In cells exposed to the extract alone, without H₂O₂, there was no significant change in reactive oxygen species (ROS) levels compared to a non-treated control. Keratinocytes pre-incubated with three different concentrations of peel extract (25, 50, and 100 µg/mL) for 24 h before H₂O₂ exposure showed significantly decreased levels of ROS compared to ones treated with H₂O₂ alone. All three examined concentrations showed a similar decrease in ROS production. In the cell line treated with spray-dried peel extract without lipopolysaccharide (LPS), there was no significant change in the expression of interleukin 1β or macrophage inhibitory factor (MIF), indicating the absence of any pro-inflammatory effects from the extract. In the LPS-treated cells, the extract significantly reduced interleukin 1β and MIF expression when pre-incubated for 24 h compared to LPS alone, confirming the anti-inflammatory potential of the extract against an LPS challenge. Additionally, the extract provided a sun protection factor (SPF) of 11.33±0.33 (at a concentration of 100 µg/mL), and significantly lower SPF values, 3.11±0.05 and 5.97±0.21, at lower concentrations (25 and 50 µg/mL, respectively), while an SPF of 6 is generally considered the minimum degree of UVB protection required for sunscreen products.