Six new
ent-kaurane-type diterpenoids were isolated from the leaves of the endemic Vietnamese medicinal plant
Croton tonkinensis G
AGNEP. (Euphorbiaceae) together with three known
ent-11α-acetoxy-7β,14α-dihydroxykaur-16-en-15-one (1),
ent-kaur-16-en-15-one 18-oic acid (5) and
ent-18-hydroxykaur-16-ene (7). Their structures were determined by spectroscopic analyses to be
ent-7β-acetoxy-11α-hydroxykaur-16-en-15-one (2),
ent-18-acetoxy-11α-hydroxykaur-16-en-15-one (3),
ent-11α-acetoxykaur-16-en-18-oic acid (4),
ent-15α,18-dihydroxykaur-16-ene (6),
ent-11α,18-diacetoxy-7β-hydroxykaur-16-en-15-one (8), and
ent-(16
S)-1α,14α-diacetoxy-7β-hydroxy-17-methoxykauran-15-one (14).
ent-Kaurane-type diterpenoids from
Croton tonkinensis 2—4, 6, and 9—13, were tested for toxicity in the brine shrimp lethality assay. Compounds 9, 10, and 12 demonstrated significant activity, compounds 2, 3, 6, and 11 showed weak activity, and compounds 4 and 13 were inactive.
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