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

Abstract

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.