The effect of furocoumarins on terpene photo-oxidation under UV-A light was investigated. For this purpose, four furocoumarins (8-methoxypsoralen, bergapten, bergaptol, bergamottin) each at a level of 5%, was added to solutions of the terpenes β-pinene, R-(+)-limonene and γ-terpinene in ethanol followed by UV irradiation at 366 nm. Bergaptol and bergamottin were synthesized and fully elucidated by NMR spectroscopy. UV-induced transformation of all terpenes was substantially reduced in the presence of furocoumarins. Best photo-protection was observed for γ-terpinene with the addition of bergaptol, i.e. degradation was reduced by 73% compared to the neat substance over a time period of ten days. Bergamottin (50.2%), bergapten (39.8%) and 8-methoxypsoralen (39.6%) also reduced degradation substantially. The protective effect of bergaptol was even noticeable at low concentrations of 0.1%. The main oxidation product of γ-terpinene was p-cymene. Limonene and β-pinene showed a predominated hydroperoxide formation under UV light which could almost completely prevented in the presence of furocoumarins. The protective effect of furocoumarins was presumably due to energy dissipation as a result of the conversion of high energetic radiation (UV-A) into visible light via fluorescence. Phosphorescence or self-quenching within the triplet state were further mechanisms avoiding reactions of excited furocoumarins with the terpenes under investigation. Hence, the photo-stability of the furocoumarins themselves correlated with the extent of their protective effect on all three terpenes.

研究了呋喃香豆素在 UV-A 光下对萜烯光氧化的影响。为此，将每种含量为 5% 的四种呋喃香豆素（8-甲氧基补骨脂素、佛手柑、佛手柑醇、佛手柑）添加到萜烯β-蒎烯、R -(+)-苎烯和γ-萜品烯的乙醇溶液中，然后通过 366 nm 的紫外线照射。合成了佛手柑醇和佛手柑，并通过核磁共振光谱进行了充分阐明。在呋喃香豆素的存在下，所有萜烯的紫外线诱导转化均显着降低。观察到γ 的最佳光保护-萜品烯添加了香柠檬醇，即与纯物质相比，在十天的时间内降解减少了 73%。佛手柑 (50.2%)、佛手柑 (39.8%) 和 8-甲氧基补骨脂素 (39.6%) 也大大减少了降解。bergaptol 的保护作用在 0.1% 的低浓度下甚至很明显。γ-萜品烯的主要氧化产物是对伞花烃。柠檬烯和β-蒎烯在紫外光下显示出主要的氢过氧化物形成，这在呋喃香豆素的存在下几乎可以完全阻止。呋喃香豆素的保护作用可能是由于高能辐射 (UV-A) 通过荧光转化为可见光而导致的能量耗散。三重态内的磷光或自淬灭是避免兴奋的呋喃香豆素与所研究的萜烯反应的进一步机制。因此，呋喃香豆素本身的光稳定性与其对所有三种萜烯的保护作用程度相关。