New cinnamic acid sugar esters as potential UVB filters: Synthesis, cytotoxicity, and physicochemical properties.

Summary

A synthetic series of cinnamic acid sugar esters (glucose, ribose, lactose) was prepared and screened for UV-Vis properties, lipophilicity, and cytotoxicity. Most were non-cytotoxic; a ribose-derived analog (3k) with a 4-methoxy substituent achieved higher in vitro SPF than ethylhexyl methoxycinnamate (EHMC) and showed superior antioxidant and keratinocyte-protective effects.

Key Findings

• Synthesized a panel of cinnamic acid sugar esters (glucose, ribose, lactose) via oxidative alkoxycarbonylation routes.
• Most compounds were non-cytotoxic at tested concentrations.
• UV-Vis absorption profiles depended on aromatic substituents.
• Compound 3k (4-methoxy phenyl, 1,2-O-isopropylidene ribose) showed higher in vitro SPF than EHMC.
• Compound 3k exhibited stronger antioxidant activity and protected keratinocytes.

Clinical Implications

If validated in vivo with favorable photostability, penetration, and safety profiles, cinnamic acid sugar esters could expand sunscreen filter options, potentially improving protection and tolerability for diverse skin types.

Limitations

• Efficacy measured via in vitro SPF; no in vivo photoprotection or photostability data presented.
• Long-term safety, skin penetration, and regulatory readiness remain unassessed.

Future Directions

Assess photostability, in vivo SPF/UVA-PF, dermal absorption, and safety; optimize formulation (e.g., encapsulation) and scale-up synthesis; evaluate broad-spectrum coverage and combination performance.