/ \_O_|
| | HO| |
| |OH HO| |
\ / \ /
\/ \/
OH OCH_{3}

=Scopolin=, C_{22}H_{28}O_{14}, found in _Scopolia japonica_, contains two
glucose molecules united to a monomethyl ether of aesculin; while
=limettin=, found in certain citrus trees, is the dimethyl ether of
aesculin.

THE PIGMENT GLUCOSIDES

Many, if not all, of the red, yellow, violet, and blue pigments of plants
either exist as, or are derived from, glucosides. These are of three types:
the madder, or alizarin, reds are derivatives of various
oxy-anthraquinones; most of the soluble yellow pigments are glucosides
derived from flavones or xanthones; and the soluble red, blue, and violet
pigments of the cell-sap of plants are mostly anthocyan derivatives. The
four basic groups, or nuclei, which are present in these different types of
compounds are complex groups consisting essentially of two benzene rings
linked together through a third ring in which there are either two oxygen
atoms in the ring, or one oxygen in the ring and a second attached to the
opposite carbon in the (C=O) arrangement, as shown by the following
diagrammatic formulas:

Xanthone Anthraquinone

O O
| 1 1 | 1'
/\ C /\ /\ C /\
/ \ / \ / \ / \ / \ / \
| | | |2 2| | | |2'
| | | |3 3| | | |3'
\ / \ / \ / \ / \ / \ /
\/ O \/ \/ C \/
4 4 | 4'
O

Flavone Anthocyan

1 1
/\ O 5'____4' /\ O 5'____4'
/ \ / \____/ \ / \ / \____/ \
2| | | \____/3' 2| | | \____/3'
3| | |5 1'