STEROLS OF SOME DIATOMS

Sterols were identified from seven species of axenically cultured diatoms which may be used for oyster food. Five species contained 24-methylenecholesterol as the major sterol. Stigmasterol was the principal sterol in Amphora coffaeformis while 24-ethylcholesterol was the major sterol in Navicula pelliculosa. Each of the four species of the order Centrales had 24-methylcholesterol, which was all 22-dihydrobrassicasterol (24-beta-methyl epimer). The 24-methyl-cholesterol from Nitzschia brevirostris (order Pennales) was all campesterol (24-alpha-methyl epimer). From this and previously published works on diatom sterols, it appears that sterols from the order Centrales are 24-beta-oriented and those from the order Pennales are 24-alpha-oriented.