n glucosides in which the other characteristic group is a
sulfur-containing compound. These glucosides yield "mustard oils" when they
are hydrolyzed by the enzyme _myrosin_, which accompanies them in the
plant. The following glucosides, found in the seeds of white and black
mustard, are the best-known representatives of this class.

=Sinigrin=, C_{10}H_{16}O_{9}NS_{2}K, found in black mustard seeds, when
hydrolyzed yields glucose, acid potassium sulfate, and allyl
isosulfocyanide (mustard oil), as indicated by the equation.

C_{10}H_{16}O_{9}NS_{2}K+H_{2}O = C_{6}H_{12}O_{6} +
C_{3}H_{5}N[trb]C=S+KHSO_{4}.

The acid potassium sulfate group separates first and most readily, leaving
a compound known as _merosinigrin_, for which the following formula has
been suggested:

-----O------
| |
CH_{2}OH.CHOH.CH.CHOH.CH.CH
| |
O S
| /
|/
C=N[trb]C_{3}H_{5}

This compound usually breaks down into glucose and mustard oil; but by
special treatment it is possible to obtain from it thioglucose,
C_{6}H_{11}O_{5}.SH. This indicates that in the original glucoside the
glucose is linked with the mustard oil through the sulfur atom.

=Sinalbin=, C_{30}H_{42}O_{15}N_{2}S_{2}, from white mustard seeds, when
hydrolyzed by myrosin, yields glucose, sinalbin mustard oil (a
paraoxybenzyl derivative of allyl isosulfocyanide) and sinapin acid
sulfate; according to the equation

C_{30}H_{42}O_{15}N_{2}S_{2}+H_{2}O = C_{6}H_{12}O_{6}+C_{7}H_{7}O.NCS
Sinalbin Glucose Sinalbin mustard oil

+ C_{16}H_{24}O_{5}N.HSO_{4}.
Sinapin acid sulfate

The sinalbin mustard oil may be represented by the formula
____
/ \
HO-CH CH-CH_{2}NCS. Hydrolysis of the sinapin acid sulfate converts
\____/
it into sinapinic acid, C_{6}H_{2}OH.(OCH_{3})_{2}.CH=CH.COOH, choline,
N(CH_{3})_{4}C_{2}H_{4}OH (see page 152), and H_{2}SO_{4}. It is,
therefore, a very complex glucoside.

TEE DIGITALIS GLUCOSIDES