RESUMO
5α,8α-peroxyergosteryl divaricatinate (1) is isolated for the first time from acetone extract of the thallus of Cladonia cf. didyma together with condidymic (2), isodidymic (3) and barbatic (4) acids. Their UVB/UVA photoprotective and antioxidant activities were determined along with their cyto- and DNA-protecting actions against OH⢠damage. Compound 1 showed high UVA, cyto- (%cell viability ca. 82 at 15 µM vs 71 for OHâ¢) and DNA (%DNA-integrity ca. 74 at 100 µM vs 22 for OHâ¢) protecting properties. Compounds 2 and 3 exhibited high UVB (SPF ca. 40) and antioxidant activities (free radical scavenging potency EC50 = 0.6694 and 1.700 mol compound/mol DPPHâ¢; ferric reducing power 0.392 and 0.546, at 500 ppm and inhibited lipid peroxidation); protecting cells (%cell viability ca. 76 at 15 µM) and DNA (%DNA-integrity ca. 57 at 100 µM). Compounds 1 to 3 fulfilled some physicochemical properties to act topically on the skin.
RESUMO
The new hypotrachynin A (1) and B (2) along with the known (+)-(9b-R)-usnic (3) and methylstictic acids (4) were isolated for the first time from Hypotrachyna caraccensis. Additionally, their potency and reactivity as DPPH⢠scavengers was determined by a kinetic study calculating their EC50 and second-order rate constants (k2). Considering 1-4 could be dermatological agents, their n-octanol-water partition coefficients and standard molar Gibbs free energies of transfer were calculated as estimation of their lipophilicity and skin penetration. Compounds 1, 3 and 4 were less potent than 2 (EC50 = 3.3014; 1.7540; 2.6652 vs 0.7376) as DPPH⢠scavengers, in turn 4, was the most reactive with a comparable k2 to the antioxidant BHT (k2 = (232 ± 24) × 10-2 vs (564 ± 12) × 10-2 M-1 s-1, respectively). Since 2 and 4 had an optimal lipophilicity and permeability for skin penetration, they might be developed as topical ingredients to prevent oxidative damage.