Augmented Hybrid Sunscreen Incorporating Myrothamnus flabellifolius and Citrullus lanatus: A Pre-Clinical Investigation

The sun emits radiation with different ionising energies in a wide spectrum of wavelengths, frequencies and energies inflicting various forms of actinic damage to dermal structures. Damage can either be direct DNA damage through alteration of gene expression and compromised inflammatory responses or indirectly through the generation of free radicals, causing tissue damage through protein oxidation, deactivation and lipid peroxidation. Sunscreens and physical barriers are the main forms of protection from actinic damage. However, recent studies confirm that chemical sunscreens have serious bio safety issues while, physical sunscreens which are deemed safer have limited use due to unesthetic white casts. To mitigate these issues, we aimed to develop safer, amplified photoprotection through augmenting nanometric physical sunscreens with oil extracts from natural photoprotective tropical plants; Myrothamnus flabellifolius and Citrullus lanatus. First, we evaluated in-vivo, the oils comedogenic potential as well as their genotoxic and mutagenicity potential through the Ames reverse mutation test. We further evaluated the skin sensitivity and irritation potential of the augmented sunscreen using Draize tests and human patch testing. We also investigated in vitro the emulsion SPF, UVAPF, photoprotective efficiency and critical wavelength (ƛC). Our findings show that photoprotective oils investigated are non-comedogenic. Neither concentration of the tested oils is genotoxic or mutagenic with or without metabolic activation. Skin sensitivity and irritation tests confirmed that the resulting augmented sunscreen does not sensitise or irritate skin in basic topical cosmetic use. The augmented sunscreen had a high SPF of 30, UVAPF of 14, UVAPFeff and SPFeff both above 97% and ƛC of 383. Based on the foregoing we concluded that the development of an amplified, broad-spectrum and biologically safe augmented sunscreen incorporating C Lanatus and M flabellifolius oils is feasible and heralds’ new perspectives in formulation of efficacious nonconventional photoprotective products.