Seven new 17-norpimarane and (9βH)-17-norpimarane diterpenoids, icacinlactones A-G (1-7), were isolated from the tuber of Icacina trichantha. The structures were elucidated by spectroscopic and HRMS techniques, and the absolute configuration of 2 was determined by means of X-ray crystallographic analysis. Compounds 1-7, as well as four known related structures, were evaluated for cytotoxic activity against MDA-MB-435 (human melanoma cancer), MDA-MB-231 (human breast cancer), and OVCAR3 (human ovarian cancer) cell lines. Several of these natural products displayed significant cytotoxic activity, with humirianthenolide C being most active.
The tuber of Zcacina trichantha was extracted with 50% methanol and concentrated to dryness in uacuo to give a yield of 5.6% w/w. The extract induced sleep in rats treated with high doses (400-1O00 mg/kg i.p.). The LDw of the extract was 671 mg/kg i.p. It potentiated pentobarbitone sleeping time in rats dose-dependently and also induced significant local anaesthetic effects in guinea-pigs. The extract was able to give 80% protection to rats poisoned with pentylenetetrazole but failed to protect rats from strychinine poisoning. It induced significant dose-dependent analgesia in rats and showed significant muscle relaxant activity in mice.
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