New ent-kauran diterpene and antioxidant components from the seed of Ipomoea nil

One new ent-kauran diterpene, 7β,16β,17-trihydroxy ent-kauran 19-(6β)-olide (1), along with eight known compounds were isolated from the seed of Ipomoea nil. Isolates caffeoylquinic acid derivatives 5-9 were found for the first time in this species. All structures were identified from various spectroscopic data. trans-Caffeic acid 3, phenylpropanoid 4, and caffeoylquinic acid derivatives 5-9 could inhibit ROS generations induced in human keratinocyte HaCaT cells with IC₅₀ values of 0.94-28.40 μM. Compounds 3 and 5-9 also had DPPH free radical scavenging properties (IC₅₀ values, 14.86-68.27 μM), however, isolate 4 did not show inhibition effect. Generally, I. nil and its secondary metabolites 3-9 could be further applied for oxidative stress damage resulted in skin disorders.