Chemical and bioactivity of flavanones obtained from roots of Dalea pazensis Rusby.

Two new prenylated flavanones, pazentin A (3',4'-dihydroxy-6,2'-diprenylpinocembrin, 1) and pazentin B [4'-hydroxy-2'-methoxy-5'-(1‴, 1‴-dimethylallyl)-6-prenylpinocembrin, 2] together with two known ones (3 and 4) previously isolated from other Dalea species were obtained from the benzene extract of Dalea pazensis Rusby roots. The compounds were evaluated in vitro for their inhibition on mushroom tyrosinase enzyme and in relation to their effect on melanogenesis in B16 murine melanoma cells, by using a spectrophotometric method. The information obtained could be relevant to the knowledge of the structure-activity relationship for these flavonoids with the aim to explore the rational design for skin-whitening agents.