Ent-clerodane and ent-trachylobane diterpenoids from Croton dictyophlebodes

The stem bark and root bark extracts of Croton dictyophlebodes (Euphorbiaceae) yielded seven undescribed ent-clerodanes: 15,16-epoxy-17,12(S)-olide-ent-cleroda-1,3,13(16),14-tetraen-18-oic acid methyl ester (crotodictyo A), 3β,4β:15,16-diepoxy-ent-cleroda-13(16),14-dien-20-al (crotodictyo B), 3β,4β:15,16-diepoxy-ent-cleroda-13(16),14-dien-19,20-dioic acid (crotodictyo C), 3β,4β:15,16-diepoxy-ent-cleroda-13(16),14-dien-20,19-olide (crotodictyo D), 3β,4β:15,16-diepoxy-20,12(R)-olide ent-cleroda-13(16),14-dien-19-oic acid methyl ester (crotodictyo E), 15,16-epoxy-ent-cleroda-3,13(16),14-trien-12-oxo-18-oic acid (crotodictyo F) and 15,16-epoxy-ent-cleroda-1,3,13(16),14-tetraen-12-oxo-18-oic acid (crotodictyo G), in addition to 15,16-epoxy- ent-cleroda-3,13(16),14-trien-12-oxo-18-oic acid methyl ester (crotodictyo H), reported previously as a synthetic derivative, and acetyl aleuritolic acid. The root extract yielded two ent-trachylobanes, ent-trachylobane-18,19-diol, the undescribed ent-trachylobane-2α,19-diol, along with ent-kaur-16-en-19-oic acid and 2-methoxybenzyl benzoate. Compounds were evaluated against the NCI 60 panel of human tumour cell lines at a single dose of 10^-5 M, but showed no significant activity.

Keywords: Croton dictyophlebodes; Cytotoxicity screening; Electronic circular dichroism; Ent-clerodane; Ent-trachylobane; Euphorbiaceae.