長期的陽光曝晒，容易造成皮膚機能受損，加速皮膚老化，產生紅斑，甚至罹患皮膚癌。因此防晒製品乃至一般化妝品中添加紫外光吸收劑以保護皮膚，已成為潮流趨勢，但是所用的紫外光吸收劑多為合成化學品，經常造成過敏等不良副作用，使用天然紫外光吸收劑可解決此困擾。
本研究為開發天然紫外光吸收劑，利用Kumler氏所提之紫外光吸收性能評估方法，針對數種金絲桃屬植物之粗抽取物和成分，測定其遮光係數值(S.I. value) ，探討其作為紫外光吸收劑之可能性。

Exposure of the skin to sunshine for long periods of time is known to induce different degrees of erythema or skin cancer in the unprotected skin. Within recent years ultraviolet absorbers have become an important ingredient in cosmetic formulae, the majority of which are synthesized artificially. These however may induce some side effects, including allergic and inflammatory reactions, such problems may be solved by the use of natural sunscreens. This study focuses on the natural sunscreen products. The sunscreen index ( S. I. ) value of the extractions of several Hypericoideae are investigated by using Kumler's method. The ultraviolet absorption of natural sunscreen extractions are discussed.