Seven New Phenylhexanoids with Antioxidant Activity from Saxifraga umbellulata var. pectinata

Seven new phenylhexanoids, (S)-(+)-3,4-dihydroxy-11-methoxyphenylhex-9-one (1), (E) 3,4-dihydroxy-phenylhex-10-en-9-one (2), (E)-4-hydroxyphenylhex-10-en-9-one (3), (R)-(-)-3,4,11-trihydroxyphenylhex-9-one 11-O-β-d-glucopyranoside (4), (R)-(-)-4,11-dihydroxyphenylhex-9-one 11-O-β-d-glucopyranoside (5), phenylhex-4,9,11-triol 11-O-β-d-glucopyranoside (6), and 9-O-acetyl-phenylhex-4,9,11-triol 11-O-β-d-glucopyranoside (7), were isolated and identified from Tibetan medicine Saxifraga umbellulata var. pectinate. The antioxidant activities of these compounds were evaluated using the DPPH and ABTS radical scavenging experiments. In the ABTS experiment, compounds 1 (IC₅₀ 13.99 ± 2.53 μM) and 2 (IC₅₀ 13.11 ± 0.94 μM) exhibited significantly better antioxidant activity than L-ascorbic acid (IC₅₀ 23.51 ± 0.44 μM).