Complex sentence: It has to be pointed out that most of this claims have yet to be proven in clinical trials, while studies substantiated furocoumarins in several plant components; an agent known to increase skin sensitivity to sunlight and may cause dermatitis.
Split into simpler sentences: It has to be pointed out that most of these claims have yet to be proven in clinical trials, while studies have substantiated furocoumarins in several of these plants' components. Furanocumarin is an agent known to increase skin sensitivity to sunlight and may cause dermatitis.