\/
OX

=Amygdalin=, also contains a benzaldehyde group, but there is linked with
it a hydrocyanic acid group; hence, this glucoside is usually classed with
the cyanophoric glucosides (see page 86).

THE ACID GLUCOSIDES

The most common example of this group is =gaultherin=, C_{14}H_{18}O_{8},
which is found in the bark of the black birch and is a combination of
glucose with methyl salicylate. Both the glucoside itself and the methyl
salicylate ("oil of wintergreen") which is derived from it are used as
remedies for rheumatism.

=Jalapin=, C_{44}H_{56}O_{16} (glucose and jalapinic acid), and
=convolvulin=, C_{54}H_{96}O_{27} (glucose+rhodeose+convolvulinic acid),
are glucosides of very complex organic acids, found in jalap resin, which
are used in medicine as cathartics or purgatives.

THE OXY-CUMARIN GLUCOSIDES

Cumarin itself is widely distributed in plants. No glucoside containing
cumarin as such has yet been isolated; but several glucosides of its
oxy-derivatives are known. The following are common ones:

=Skimmin=, C_{15}H_{16}O_{8} (glucose and skimmetin), is found in _Skimmia
japonica_; =aesculin=, C_{15}H_{16}O_{9} (glucose and aesculetin), is found
in the bark of the horse-chestnut, _AEsculus hippocastanum_, and its isomer,
=daphnin= (glucose and daphnetin), in several species of _Daphne_; and
fraxin, C_{16}H_{18}O_{10} (glucose and fraxetin), is found in the bark of
several species of ash.

The structural arrangement of the oxy-cumarin groups which are found in
these glucosides is shown in the following formulas. It is not known to
which OH group the sugar is attached, in each case.

Skimmetin AEsculetin

CH=CH.CO CH=CH.CO
/\ | /\ |
/ \_O_| / \_O_|
| | | |
| | HO| |
\ / \ /
\/ \/
OH OH

Daphnetin Fraxetin

CH=CH.CO CH=CH.CO
/\ | /\ |
/ \_O_|