12. QUINONES: STRUCTURE AND DISTRIBUTION
MeO
Droserone
(Droseraceae)
(XLIX)
Hydroxydroserone
(Droseraceae)
(L)
9 OH
CHCH 2 CH=CMe 2
MeCO|
Me
Eleutherin^
(Iridaceae)
(LI)
OH
OMe
Alkannin
c
(Boraginaceae)
(LII)
Me
Me
Cordeauxiaquinone
(Leguminosae)
(LIII)
Me
CH 2 CH==C-h(CH 2 ) 3 CH-]3 Me
Vitamin K
(Leguminosae)
(LIV)
a For references to individual species see (I) except where indicated.
0 An optical isomer, isoeleutherin, occurs in the same plant.
c An optical isomer, shikonin, also occurs naturally (48).
lated families and have similar structures reminiscent of the emodinchrysophanol type of anthraquinone. Droserone is present with hydroxydroserone in the pseudo-bulbs of Drosera whittakerii
Planch
(29), and with plumbagin in the tuberous roots and rhizomes of D.
peltata Sm. (30). [A yellow pigment isolated along with plumbagin from
D. rotundifolia
Linn, is a flavone and not a naphthaquinone-carboxylic
acid as has been suggested (31)].
Plumbagin
(2-methyljuglone)
(XLVIII) is also found with 7-methyljuglone (XLVI) in the bark,
leaves, and fruit of Diospyros ebenum Koen (32). A third compound