Naturally occurring anhydrovitamin A2. Transformation into retinene2

Abstract

1. ;Naturally occurring anhydrovitamin A(2)' obtained from the liver oil of freshwater fish Bagarius bagarius yielded, after six-stage chromatography, a pure product showing characteristic bands at 350, 368 (E(1%) (1cm.) 1006) and 390mmu in ethanol, and producing a green colour with antimony trichloride (E(1%) (1cm.) 1884 at 693mmu). 2. On distribution of the material between light petroleum and 95% methanol, 70% of it is found in methanol, which points to its hydroxylic character. 3. It gives an acetyl derivative, from which the original hydroxy compound can be regenerated on hydrolysis. 4. The infrared spectrum shows, besides other bands, one at 3460cm.(-1) attributable to a hydroxy group. 5. On passing a light-petroleum solution of naturally occurring anhydrovitamin A(2) through manganese dioxide a 6% conversion into retinene(2) is observed. 6. A 3-hydroxyanhydroretinol structure is proposed for naturally occurring anhydrovitamin A(2) and a mechanism of its transformation into retinene(2) on this basis is suggested.

Structure and synthesis of naturally occurring anhydrovitamin A2

“…However, it was observed that even these fish liver oils occasionally contain very little of the anhydro compound (Table 2). An attempt was made to confirm the 3-hydroxyanhydroretinol structure proposed by and Barua & Nayar (1966). It was found that the naturally occurring compound is always accompanied by a large quantity of sterols, which could be separated, except for a trace (as indicated by the mass spectrum), by repeatedly cooling the methanolic solution followed by treatment with digitonin.…”

“…From these observations Balasundaram et al (1958) reported that the naturally occurring anhydrovitamin A2 differed from the synthetic anhydrovitamin A2 (3-ethoxyanhydroretinol) in not having an ethoxy group, but having a different substituent in the 8-ionone ring or possibly elsewhere. Although and Barua & Nayar (1966) have proposed a 3hydroxyanhydroretinol structure, the structure has not so far been confirmed. Vol.…”

“…It has been shown by Barua et al (1977) that the oral administration of lutein (fie-carotene-3,3'-diol) or anhydrolutein (3,4-didehydro-fl-caroten-3'-ol) to the vitamin A-depleted Saccobranchus fossilis led to the formation of 3-hydroxyretinol along with 3,4-didehydroretinol. It is probable that the naturally occurring anhydrovitamin A2 for which a 3hydroxyanhydroretinol structure has been proposed by and Barua & Nayar (1966) can arise from 3-hydroxyretinol in a similar manner to the way in which anhydroretinol is formed from retinol. A study was therefore made of the metabolism of 3-hydroxyretinol in vitamin A-depleted S. fossilis.…”

Photochemistry of Vision

“…Another possible reaction pathway yielding first 3-dehydroretinol and then retinol is summarised below (from GROSS and BUDOWSKI, 1966 0<--~ '0<-- BARUA and NAYAR (1966) suggest that dietary hydroxy-carotenoids are converted into 3-dehydroretinaldehyde by way of the intermediate "naturally-occurring anhydrovitamin A 2 ", or 3-hydroxyanhydroretinol, which has been found in…”

Preparation, properties and metabolism of retro-3-dehydroretinyl acetate

“…Vitamin A compounds possessing the retro system of conjugated double bonds have been encountered in biological samples (Balasundaram, Bamji, Cama, Sundaresan & Varma, 1958;Varma, Erdody & Murray, 1965a). The structure of the naturally occurring anhydrovitamin A2 was shown to be 3-hydroxyanhydrovitamin A1 (Barua & Nayar, 1966), whereas the chemically synthesized anhydrovitamin A2 was 3-ethoxyanhydrovitamin A1 (Henbest, Jones, Owen & Thaller, 1955a). When chemically synthesized anhydrovitamin A2 was fed to vitamin A-deficient rats, it gave rise to 'rehydrovitamin A2' (Balasundaram et al 1958;Bamji, Cama & Sundaresan, 1962).…”