Yoshinori Shiobara

Biosynthesis of anthraquinones and related compounds in Galium mollugo cell suspension cultures

Abstract From Galium mollugo cell suspension cultures, 1,4-dihydroxy-3-prenyl-2-naphtholic acid methyl ester diglucoside was isolated along with anthraquinones and mollugin. Production of the diglucoside was much increased by administering 2-succinylbenzoate to the cultures. The incorporation of 2-succinylbenzoate into lucidin-3-primeveroside, mollugin and the diglucoside in the mode so far proposed for rubiaceous anthraquinones was verified by administration of 13C-labelled 2-succinylbenzoate to the cell cultures.

Quinones and related compounds in higher plants. Part 11. Role of 2-carboxy-2,3-dihydro-1,4-naphthoquinone and 2-carboxy-2-(3-methyl-but-2-enyl)-2,3-dihydro-1,4-naphthoquinone in the biosynthesis of naphthoquinone congeners of Catalpa ovata callus tissues

Dilution analyses after administration of 14C-labelled 4-(2-carboxyphenyl)-4-oxobutanoic acid (3) to the callus tissues of Catalpa ovata demonstrated the following results: (i) 2-Carboxy-4-oxo-1-tetralone (COT), 2-carboxy-4-hydroxy-1-tetralone (CHT), prenyl-COT (4), and prenyl-CHT (5) are on the biosynthetic pathway of naphthoquinones; (ii) the route passing through COT → prenyl-COT (4)→ catalponone (6) is the main pathway of the biosynthesis of naphthoquinones, whereas there exists a subsidiary route passing through CHT → prenyl-COT (5)→ catalponol (2); (iii) regarding the key intermediates prenyl-COT (4) and catalponone (6), (2S)-prenyl-COT [(2S)-(4)] and (2R)-catalponone [(2R)-(6)] participate in the biosynthesis and both prenylation and decarboxylation proceed stereoselectively; and (iv) the acid (3) was incorporated into menaquinone-1 (7), 1-hydroxy-2-methylanthraquinone (8), 3-hydroxydehydro-iso-α-lapachone (9), etc., in the callus tissues. Furthermore, administration of 4-([carboxy-14C]-2-carboxyphenyl)-4-hydroxy[4-3H]butanoic acid (32) to the original Catalpa plant and the callus tissues revealed that (3) is cyclised to COT and then reduced to CHT.

Structural elucidation of 11-hydroxy-12,13-epoxyoctadeca-(9Z, 15Z)-dienoic acids from rice plants suffering from rice blast disease

The structures and absolute configurations of the 11-hydroxy-12,13-epoxyoctadecadienoicacids isolated from rice plants suffering from rice blast disease have been determined.

Stereochemistry of prenylation and subsequent decarboxylation in the biosynthesis of prenylanaphthoquinone congeners in callus cultures of Catalpa ovata

Abstract The main biosynthetic route from 4-(2′-carboxyphenyl)-4-oxobutanoic acid (1) via 2-carboxy-4-oxo-1-tetralone (COT) to several quinonoids in callus cultures of Catalpa ovata was definitely demonstrated to pass stereospecifically through (2S)-prenyl-COT ((2S)-2) and (2R)-catalponone ((2R)-3).

2-Carboxy-4-hydroxy-α-tetralone, a precursor for catalponol biosynthesis

Abstract 2-Carboxy-4-hydroxy-α-tetralone ( 5 ) and its methyl ester ( 10 ) were incorporated into catalponol ( 1 ) in Catalpa ovata with retention of C-4 and C-8 tritium atoms. Incorporation of the former two substances into catalpalactone ( 2 ) and 4,9-dihydroxy-α-lapachone ( 12 ) was also demonstrated.

Site of prenylation in anthraquinone biosynthesis in cell cultures of Galium mollugo

The mode of prenylation during the biosynthesis of lucidin primeveroside was elucidated by locating the 13C-label in lucidin primeveroside isolated from cell cultures of Galium mollugo, to which 4-(2′-[C13]carboxyphenyl)-4-oxobutanoic acid was administered.