A New Tetraethenoid Sterol of Yeast

Abstract

Ergosterol has long been known as the primary sterol of yeast (1) and several other yeast sterols have been reported. Smedley-MacLean (2) reported the presence of zymosterol, a dextrorotatory sterol. The structure of zymosterol was long in question until Barton (3) showed it to be 8,24-cholestadien-3/3-ol. As a consequence of the establishment of the zymosterol structure and from the recent development of theories concerning optical rotation and structure, it would appear that two other dextrorotatory sterols of yeast reported by Wieland and others (4), namely ascosterol and fecosterol, are also unsaturated at the 8(9) position. Callow (5) reported the occurrence in yeast of "a-dihydroergosterol", since shown to be 5-dihydroergosterol (6). The neosterol described by Wieland (4) appears from the work of Barton ( 7) to be a mixture of 5-dihydroergosterol and ergosterol. Cerevisterol, described by Honeywell and Bills (8) has recently been shown (9) to be 7,22-ergostadiene-3/3,5 , 6,5-triol. It therefore appears to be an oxidation product of ergosterol, but whether it is formed metabolically by yeast or whether it is formed from ergosterol by chemical oxidation during isolation of the sterols, is not clear. Wieland and Gough (10) have also described two other yeast sterols, episterol and hyposterol.The new yeast sterol we wish to report is a tetraethenoid sterol having a ring structure identical with that of ergosterol, and having a conjugated double bond system in the side chain. Although the position of the conjugated double bond system in the side chain has not been positively established, the ultraviolet and infrared absorption characteristics lead us to believe that the new sterol has one of the structures (I or II) shown. The location of the ultraviolet maximum at 230 µ and the infrared band at 11.3 µ lend credence to the presence of a vinylidene group (11). It may further be reasonable to assume that since the new sterol is a metabolic product of yeast, the enzyme systems which are involved in production of ergosterol and zymosterol would be more likely to place a second double bond in ergosterol at 24(28) than at 20(21). Hence we favor structure I and tentatively designate the new sterol as 24(28)-dehydroergosterol, or 5,7,22,24 (28)-ergostatetraen-3#3-ol. SUMMARYThe isolation of a new tetraethenoid sterol from yeast is described. Its concentration in some yeasts approximates the ergosterol content. On the basis of chemical and spectroscopic evidence, its structure is proposed to be 5,7,22,24-(28)-ergostatetraen-30-ol.Stamford, Conn.

The effects of the hypocholesteremic compound 3β‐(β‐dimethylaminoethoxy)‐androst‐5‐en‐17‐one on the sterol and steryl ester composition ofSaccharomyces cerevisiae

“…Relative retention times on three GC systems correspond to values calculated for this compound (Patterson, G.W., personal communication), and chemical ionization mass spectra revealed a molecular ion of 394, whereas spectra produced by electron impact ionization provide an m/e peak of 123 (57% of base peak), corresponding to the di-unsaturated side chain of the tetraenol. Moreover, the uv spectrum (Xmax 230 nm; other maxima at 272,281 and 294 nm) was analogous to those reported by Breivik et al (12), by Barton et al (13), and by Petzoldt et al (14). The fingerprint region of the ir spectrum in CS 2 (Vma x 1060, 1040, 967, 885, 857, 835 and 799 cm -1) compared well with that reported by Breivik et al (12).…”

“…Moreover, the uv spectrum (Xmax 230 nm; other maxima at 272,281 and 294 nm) was analogous to those reported by Breivik et al (12), by Barton et al (13), and by Petzoldt et al (14). The fingerprint region of the ir spectrum in CS 2 (Vma x 1060, 1040, 967, 885, 857, 835 and 799 cm -1) compared well with that reported by Breivik et al (12). The above UV, IR and mass spectral data also agree with those reported for ergosta-5,7,22,24(28)tetraen-3/3-ol as reported by Nes et al (15).…”

Lipid Biochemistry of Fungi and Other Organisms

“…Another compound commonly present in sterol extracts of fungi is ergosterol peroxide (5a,Sa-epidioxy-ergosta-6,22dienol) which has been idientified in extracts of Alternaria kikuchiana (Starratt, 1976), Scleroderma aurantium (Vrkoc et al, 1976), and other species (Breivak et al, 1954;Tanahashi and Takahashi, 1966;Clark and McKenzie, 1967). There is some question as to this compound being a natural product since it is only detected in extracts of piploporus betulinus and Daedalea quercina sporophores exposed to light for several days and not in fresh extracts.…”

Composition of the protoplast membrane from Saccharomyces cerevisiae

“…The major sterol in S. cerevi8iae N.C.Y.C. 366, namely A5,7,22,24(28)-ergostatetraen-3fl-ol, has, however, been detected in baker's yeast by Breivik, Owades & Light (1954), though not as a major component. It is possible, too, that the strain of S. cerevi8iae examined by Boulton (1965) contained this or a similar sterol, for the extinction of the sterol extract at 250m,t was 40% greater than would be expected if ergosterol had been the sole major sterol present.…”