2. STEROLS: STRUCTURE AND DISTRIBUTION
145
the species from which meaningful data have so far been derived. The
data include the fat content of the animal, rather vaguely expressed as
ether-, acetone-, or benzene-soluble material, the unsaponifiable fraction and its sterol content, and the most characteristic and informative
physical properties of the sterol fraction.
The fats of the starfish contain a relatively high amount of unsaponifiable matter, and the highest average, 27%, among the Phanerozonia. The considerable deviations from the average may not be due
solely to species differences or seasonal variations but more likely to
the methods used in the isolation of the unsaponifiable fraction. The
latter contains substantial quantities of batyl alcohol, which is rather
water soluble and often incompletely extracted with ether. Such incomplete extraction will in turn influence the sterol content of the unsaponifiable fraction.
The sterols of starfish were among the first animal sterols to be
recognized as different from cholesterol. Doree (6) called attention to
their peculiar properties, and Kossel (172) gave a more detailed description of the sterol of Asterias rubens, which he named stellasterol.
Many years later it was shown that the typical starfish sterol is a mixture of the monounsaturated stellastenol and the diunsaturated stellasterol (173). Such mixtures are exceedingly difficult to separate, and
the components of most of them have not yet been obtained in a convincingly uniform state. It has, however, been established beyond doubt
that both sterols possess the A
7 -double bond rather than the more
familiar Δ
5 -double bond, and that they differ only in the structure of
the side chain. Interpretation of evidence derived from ozonolysis of
the mixture led to the formulation of stellastenol as (III, R = G) and
stellasterol as its 22,23-dehydro-derivative (III, R = H) (173).
In the Japanese literature an analogous mixture of sterols derived
from other starfish was described almost simultaneously under the
name hitodesterol (20, 174). More recently the suggestion has been
made that hitodesterol from Asterias amurensis (175), and Asterias
pectinifera (176) is identical with a-spinasterol, a A
7 -sterol (III, R = K)
long known as the sterol of spinach. It is either accompanied if not replaced by other A
7 -sterols, such as A
7 -cholestenol (177) (III, R = A),
A
7 -stigmastenol (III, R = J), and a sterol such as (III, R = K) (178).
Pateriasterol (179) from Pateria (Asterina) pectinifera for which a
structure had been proposed in disagreement with its optical properties, has since been found to be identical with hitodesterol, i.e., one or
more of the A
7 -sterols (177). The name asteriasterol was given to a
low-melting unsaponifiable material from Asterias forbesi (180). Subsequent studies showed that this fraction contained only little sterol
145
the species from which meaningful data have so far been derived. The
data include the fat content of the animal, rather vaguely expressed as
ether-, acetone-, or benzene-soluble material, the unsaponifiable fraction and its sterol content, and the most characteristic and informative
physical properties of the sterol fraction.
The fats of the starfish contain a relatively high amount of unsaponifiable matter, and the highest average, 27%, among the Phanerozonia. The considerable deviations from the average may not be due
solely to species differences or seasonal variations but more likely to
the methods used in the isolation of the unsaponifiable fraction. The
latter contains substantial quantities of batyl alcohol, which is rather
water soluble and often incompletely extracted with ether. Such incomplete extraction will in turn influence the sterol content of the unsaponifiable fraction.
The sterols of starfish were among the first animal sterols to be
recognized as different from cholesterol. Doree (6) called attention to
their peculiar properties, and Kossel (172) gave a more detailed description of the sterol of Asterias rubens, which he named stellasterol.
Many years later it was shown that the typical starfish sterol is a mixture of the monounsaturated stellastenol and the diunsaturated stellasterol (173). Such mixtures are exceedingly difficult to separate, and
the components of most of them have not yet been obtained in a convincingly uniform state. It has, however, been established beyond doubt
that both sterols possess the A
7 -double bond rather than the more
familiar Δ
5 -double bond, and that they differ only in the structure of
the side chain. Interpretation of evidence derived from ozonolysis of
the mixture led to the formulation of stellastenol as (III, R = G) and
stellasterol as its 22,23-dehydro-derivative (III, R = H) (173).
In the Japanese literature an analogous mixture of sterols derived
from other starfish was described almost simultaneously under the
name hitodesterol (20, 174). More recently the suggestion has been
made that hitodesterol from Asterias amurensis (175), and Asterias
pectinifera (176) is identical with a-spinasterol, a A
7 -sterol (III, R = K)
long known as the sterol of spinach. It is either accompanied if not replaced by other A
7 -sterols, such as A
7 -cholestenol (177) (III, R = A),
A
7 -stigmastenol (III, R = J), and a sterol such as (III, R = K) (178).
Pateriasterol (179) from Pateria (Asterina) pectinifera for which a
structure had been proposed in disagreement with its optical properties, has since been found to be identical with hitodesterol, i.e., one or
more of the A
7 -sterols (177). The name asteriasterol was given to a
low-melting unsaponifiable material from Asterias forbesi (180). Subsequent studies showed that this fraction contained only little sterol