2. STEROLS: STRUCTURE AND DISTRIBUTION
125
these, chondrillasterol (III, R = M) is the only A
7 -sterol known to
occur in sponges (86). Aptostanol, m.p. 135°, [a] D +22°; acetate, m.p.
134°, [a] D +15°, is an unusual saturated sterol which occurs as the
principal component in the sterol mixtures from several sponges of the
family of Suberitidae (87). It was originally believed to be an isomer of
ergostanol (IV, R = E), but it now appears more probable that it is an
isomer of cholestanol (IV, R = A). Another sponge sterol of unknown
structure is haliclonasterol (88), m.p. 141°, [a] D —42°; acetate, m.p.
141°, [a] D —46°. It gives an unusually characteristic acetate dibromide.
The acetates of nearly all the unresolved sponge sterol mixtures show
optical rotations sufficiently negative to indicate the predominance of
A
5 -unsaturated sterols (II).
As yet no sponges devoid of sterols have been found. In some
keratinous sponges, however, the sterol content of the unsaponifiable
fraction and of the total sponge is below the average for all sponges.
These sponges, which are all members of the family of Spongiidae, when
freshly caught discharge profusely a viscous liquid called gurry by the
sponge fishermen. It contains about one-fourth of the total organic
matter of the sponge and roughly one-half of its fat (8). This liquid,
and the low sterol content, set these sponges apart from all others, including those of the family Verongiinae. The latter contain A
5 -sterol
mixtures in considerable amounts. It appears reasonable therefore to
regard the Verongiinae as a separate family rather than a subfamily of
Spongiidae. In its sterol content, and particularly the presence of
cholesterol, the genus Verongia seems closely related to genus Ianthella
of the family Dysiidae.
Studies on seven species of the genus Halichna (order Haposclerina) have revealed a surprising lack of uniformity of sterols. While
the sterol mixtures from H. oculata contain mainly 24-methylenecholesterol (chalinasterol) (II, R = D), the principal sterol of H.
variabilis is poriferasterol (II, R = M), and the same sterol and
clionasterol (II, R = L) are the major sterols of H. permottis and H.
coerulescens. The sterol mixtures from H. rubens and H. viridis contain
cholesterol in excess of 50%, and H. longleyi in contrast is the only
known sponge to produce the unusual haliclonasterol (88).
At present approximately one hundred species have been assigned
to the genus Haliclona. It appears to be a catchall, a polyphyletic
aggregation of species and in need of a long overdue reappraisal. Any
future revision of this genus might well take into account differences in
sterol content, which suggest division into cholesterol, poriferasterol
and clionasterol, 24-methylenecholesterol, and haliclonastrol bearing
species.
125
these, chondrillasterol (III, R = M) is the only A
7 -sterol known to
occur in sponges (86). Aptostanol, m.p. 135°, [a] D +22°; acetate, m.p.
134°, [a] D +15°, is an unusual saturated sterol which occurs as the
principal component in the sterol mixtures from several sponges of the
family of Suberitidae (87). It was originally believed to be an isomer of
ergostanol (IV, R = E), but it now appears more probable that it is an
isomer of cholestanol (IV, R = A). Another sponge sterol of unknown
structure is haliclonasterol (88), m.p. 141°, [a] D —42°; acetate, m.p.
141°, [a] D —46°. It gives an unusually characteristic acetate dibromide.
The acetates of nearly all the unresolved sponge sterol mixtures show
optical rotations sufficiently negative to indicate the predominance of
A
5 -unsaturated sterols (II).
As yet no sponges devoid of sterols have been found. In some
keratinous sponges, however, the sterol content of the unsaponifiable
fraction and of the total sponge is below the average for all sponges.
These sponges, which are all members of the family of Spongiidae, when
freshly caught discharge profusely a viscous liquid called gurry by the
sponge fishermen. It contains about one-fourth of the total organic
matter of the sponge and roughly one-half of its fat (8). This liquid,
and the low sterol content, set these sponges apart from all others, including those of the family Verongiinae. The latter contain A
5 -sterol
mixtures in considerable amounts. It appears reasonable therefore to
regard the Verongiinae as a separate family rather than a subfamily of
Spongiidae. In its sterol content, and particularly the presence of
cholesterol, the genus Verongia seems closely related to genus Ianthella
of the family Dysiidae.
Studies on seven species of the genus Halichna (order Haposclerina) have revealed a surprising lack of uniformity of sterols. While
the sterol mixtures from H. oculata contain mainly 24-methylenecholesterol (chalinasterol) (II, R = D), the principal sterol of H.
variabilis is poriferasterol (II, R = M), and the same sterol and
clionasterol (II, R = L) are the major sterols of H. permottis and H.
coerulescens. The sterol mixtures from H. rubens and H. viridis contain
cholesterol in excess of 50%, and H. longleyi in contrast is the only
known sponge to produce the unusual haliclonasterol (88).
At present approximately one hundred species have been assigned
to the genus Haliclona. It appears to be a catchall, a polyphyletic
aggregation of species and in need of a long overdue reappraisal. Any
future revision of this genus might well take into account differences in
sterol content, which suggest division into cholesterol, poriferasterol
and clionasterol, 24-methylenecholesterol, and haliclonastrol bearing
species.