Naturally occurring quinones. Part 28. Sesquiterpenoid quinones and related compounds from Hibiscus tiliaceus

The heartwood of H. tiliaceus is red and fades on exposure to light. Like H. elatus heartwood, which behaves similarly, it contains hibiscones A–D and hibiscoquinones A–D; one sample which was devoid of red pigments contained lapachol while roots (from Brazil) contained gossypol, and mansonones D and F.Hibiscoquinone B can be obtained from hibiscones C and D by autoxidation in alkaline solution, and the formation of other hibiscoquinones can be accounted for by related processes. It is suggested that the hibiscoquinones are derived in vivo from the hibiscones.