The structure of zizannin-A and -B, C25-terpenoids isolated from

Cytotoxic sesterterpenes, 6-epi-ophiobolin G and 6-epi-ophiobolin N, from marine derived fungus Emericella variecolor GF10

“…The liquid culture of the GF10 strain in the MG medium produced ophiobolins in poor yield (0.1 -0.6 mg/L for compounds 1 -4, 2-3 mg/L for compounds [5][6][7][8]. On the other hand, the culture in the solid-state medium based on cereals produced ophioblins in higher yield.…”

“…The EtOAc soluble portion of the 2-butanone extracts of these cultures were fractionated by silica gel column chromatography and purified by reversed-phase HPLC to obtain two new sesterterpenes named 6-epiophiobolin G (1) and 6-epi-ophiobolin N (3) together with six known sesterterpenes. The structures of the six known sesterterpenes were identified as ophiobolin G (2), 7 ophiobolin H (4), 7 6-epi-ophiobolin C (5), 8 ophiobolin C (6), 8,9 6-epi-ophiobolin K (7), 10 due to one aldehyde proton, five olefinic protons, four singlet methyl protons (three for vinylic methyls and one for angular methyl), and one doublet methyl protons. Detailed interpretation of a combination of 1 H-1 H COSY, HMQC, and HMBC spectral data of 1 revealed that 1 is a sesterterpene having a tricyclic ophiobolane skeleton, 1 which consists of one each of ketone and aldehyde, eight olefinic carbons (five of them are carbons bearing a proton, and other three are quaternary carbons), one quaternary carbon, five methine carbons, four methylene carbons, and five methyl carbons.…”

“…KS3. 5,6 Further study led us to the isolation of two new ophiobolins, 6-epi-ophiobolin G (1) and 6-epi-ophiobolin N (3), and six known ophiobolins, ophiobolin G (2), 7 ophiobolin H (4), 7 6-epiophiobolin C (5), 8 ophiobolin C (6), 8,9 6-epi-ophiobolin K (7), 10 and ophiobolin K (8) 10 from the culture broth of the marine derived fungus, Emericella variecolor GF10. This paper presents the isolation of these compounds and the structural elucidation of 6-epi-ophiobolin G (1), ophiobolin G (2), 6-epi-ophiobolin N (3), and ophiobolin H (4).…”

Sesterterpenoids with Anticancer Activity

“…Ophiobolin A (Fig. 3, Table 1) was the first member of the group independently isolated from Bipolaris oryzae (fungus) by Canonica et al [19] and Nozoe et al [20]. In addition to ophiobolin A, several additional analogues were isolated in the late sixties.…”

X-ray studies of C25 terpenoids. III. The crystal structure of ceroplastol I p-bromobenzoate

“…Of the several ophiobolins known to date (Fig. l) (ophiobolin A from the Cochliobolus miyabeanus and Helminthosporium species (Nozoe, Morisaki, Tsuda, Iitaka, Takahashi, Tamura, Ishibashi & Shirasaka, 1965); ophiobolin B (zizanin B; Nozoe, Hirai & Tsuda, 1966) Furthermore, the absolute configurations at C(6), C(10) and C(ll) are opposite to those found in the ophiobolins A, B and C. In ophiobolin D, the situation is the same as in the other ophiobolins except around C(6), where C(7) is bonded through a double bond. Bond lengths and angles found in the molecule of ceroplastol I p-bromobenzoate are shown in Figs.…”