Clinical Studies
The photoprotective effect of oral P. leucotomos extract has been studied in healthy human volunteers.28 Participants with Fitzpatrick skin types II to III (N=9) were exposed to gradually increasing doses of UV radiation from a xenon arc lamp emitting wavelengths between 305 and 400 nm, in a manner similar to that used to determine the MED. Exposures were then repeated after oral administration of two doses of P. leucotomos capsules (7.5 mg/kg each). There was a significant decrease in the mean erythema response at 24 hours in P. leucotomos-treated patients (P <0.01). Consistent with its photoprotective effect there were significantly fewer sunburn cell numbers (P < .05), cyclobutane pyrimidine dimers (P <.001), proliferating epidermal cells (P < .001), dermal mast cell infiltration in biopsy specimens (P < .05) compared to those of untreated patients.
A marker of chronic UVA radiation in fibroblasts and keratinocytes is a mitochondrial DNA deletion known as the common deletion.29 In a study designed to assess the effects of P. leucotomos on the common deletion in human subjects exposed to UVA,30 ten healthy adult volunteers were then exposed to doses of UVA radiation ranging from 10-35 J/m2 from an artificial UVA light source. One week later subjects were randomized to either receive or not receive oral P. leucotomos, 240 mg given 8 and 2 hours prior to UVA exposure. An adjacent area of skin was shielded from exposure. Skin biopsies taken twenty-four hours after irradiation, showed that mean common deletion values in the untreated group increased by 160% over baseline while the mean common deletion values in the P. leucotomos-treated group decreased by 42% (P=0.06). At three times the MED for UVA, values of the common deletion showed increases of 703% and 102%, respectively (P=0.07). These results are graphically displayed in the Figure.
Two studies have assessed the beneficial effects of P. leucotomos extract in patients with polymorphic light eruption (PLE). In the first study, patients with PLE and 2 subjects with solar urticaria were treated with oral P. leucotomos 480 mg daily.31 Of the 25 evaluable PLE participants, 80% improved; 31% reported that their response to sunlight normalized, 13% had clear improvement, and 36% had slight improvement. The improvement was statistically significant by C2 analysis (P<0.05). P. leucotomos was not effective in the two solar urticarial patients. The only adverse event was a worsening of irritable bowel syndrome in one patient. Otherwise oral P. leucotomos was well tolerated.
The objective of the second study also was to determine whether P. leucotomos extract could prevent or delay polymorphous light eruption lesions. In these experiments, an artificial light sources were employed for more detailed examination and quantitation of the wavelength bands affected by P. leucotomos.4 Subjects with long-standing polymorphous light eruption were enrolled. Thirty patients were identified in
whom PLE lesions could be reproduced by repeated UVA exposure. In 18 of those 30 patients, PLE could also be provoked by UVB. There were no subjects in whom PLE could be induced by UVB only. These patients then began treatment with oral P. leucotomos based on body weight: patients weighing ≤ 55 kg received 720 mg daily, those weighing 56-70 kg received 960 mg daily and those weighing > 70 kg received 1200 mg daily of P. leucotomos. After two weeks of P. leucotomos treatment, repeat photoprovocation studies were performed. P. leucotomos was continued during the photoprovocation testing. Of the 30 subjects, P. leucotomos completely blocked PLE lesion development in 9 following UVA photoprovocation (ie. 30%), and in 5 of the 18 subjects following UVB photoprovocation (28%). Of those patients who were not completely protected with P. leucotomos, partial protection occurred. Specifically, the mean number exposures required to produce PLE lesions increased from 1.95 to 2.62 for UVA (P=0.05) and from 2.38 to 2.92 for UVB (P=0.047).
A randomized, double-blind study was designed to determine whether the use of P. leucotomos extract could reduce the use of topical corticosteroids in children and adolescents with atopic dermatitis2. The study enrolled 105 patients who were receiving topical corticosteroids at the time of entry into the study to treat moderate atopic dermatitis. In addition to their standard treatment, patients were randomized to receive P. leucotomos extract
