research Pre‐clinical evidences for the efficacy of tryptanthrin as a potent suppressor of skin cancer 36 citations , October 2019 in “Cell Proliferation” Tryptanthrin effectively suppresses non-melanoma skin cancer and is safe for normal skin.
research Tryptophan in human hair: correlation with pigmentation 16 citations , August 2000 in “Il Farmaco” Men have more tryptophan in their hair than women, and it increases with age and is higher in darker and grey or white hair.