Flavan-3.4-diols and Leuco-anthocyanidins of Guibourtia spp.

Abstract

PROBABLY the most interesting of the large number of heartwood specimens previously examined¹ on two-way paper chromatograms by the toluene-p-sulphonic acid reagent^1,2 are the extractives of some of the species of the genus Guibourtia, previously known as Copaifera. Those extractives of Guibourtia coleosperma, G. tessmannii and G. demeusei which are soluble in methanol, for example, redden rapidly on exposure to direct sunlight and furnish high yields of anthocyanidins when treated with 3 N hydrochloric acid/propan-2-ol (1:5) under pressure³ (about 8 per cent yield) or under anhydrous conditions with N/40 hydrochloric acid⁴ (about 13 per cent yield). These extractives may be fractionated into a high proportion of tannins insoluble in water and with an average molecular weight of about 2,200, and a low proportion of polyphenols and carbohydrates soluble in water. Examination of the latter fraction with the toluene-P-sulphonic acid spraying reagent on two-way paper chromatograms shows the probable presence of flavan-3.4-diols with R _F values corresponding to 0.45–0.55 in 2 per cent acetic acid (second irrigant), but with differing R _F values in the partitioning mixture used (butan-2-ol saturated with water: first irrigant)⁵.