This study aimed to clarify the feasibility of utilizing spruce inner bark extract as a sun protection agent in sunscreens. Ultrasound-assisted extraction with 60 v-% ethanol was applied to isolate the extract in 25-30 % yield, that was almost independent of the temperature (45-75 oC) and time (5-60 min) of the treatment. However, the yield of stilbene glucosides, measured by UV absorption spectroscopy, was highest after ca. 20 min extraction. Nuclear magnetic resonance spectroscopy of the extract showed that it consisted mainly of three stilbene glucosides, astringin, isorhapontin and polydatin (piceid). The maximum overall yield of the stilbene glucosides was > 20 %. Extraction with water gave a much lower yield of the stilbene glucosides.
Sunscreens composed of a mixture of vegetable oils, surfactants (fatty acids), glycerin, water and the bark extract were prepared with the low-energy emulsification method. The performance of the sunscreens was assessed by spreading them on a photosensitive paper and observing the change in color during exposure to light. Commercial sunscreens with known SPF values (15-50) were used as references. Addition of 2-5 % of the bark extract in the sunscreen provided similar protection against UV light compared to the commercial products.
Use of the spruce inner bark extract as the sun protection agent in sunscreens appeared to be potentially feasible and should be studied further
