----CO.O----
^ ---------- ^ OH
| | | |
HO V OH HOOC V OH
OH OH

It is obtained by extracting myrabolams for one hour and a half, under
reflux condenser, with pyridine, filtering and adding twice the volume
of water to the filtrate and boiling till complete solution is
obtained. After about thirty hours a reddish powder deposits, from which
ellagic acid may be extracted with pyridine; the mother-liquor on being
concentrated yields luteic acid. It is also obtained by oxidising tannin
with hydrogen peroxide, the other oxidation product being ellagic acid,
and the two may then be separated as indicated above. Luteic acid forms
reddish needles which are decomposed, with evolution of gas, at
338 -341 C. Heated with 10 per cent. caustic soda solution it yields
ellagic acid. In pyridine solution the carboxyl group maybe eliminated
by hydrogen iodide, whereby pentoxybiphenylmethylolide is formed as long
silky needles, which do not melt below 300 C. The same substance may
also be obtained when ellagic acid is boiled with concentrated caustic
potash solution. When luteic acid is treated with diazomethane, it
yields the methyl ester of pentamethoxybiphenylmethylolidcarboxylic
acid.


4. DEPSIDES

The most common decomposition products of the natural tannoids are
hydroxybenzoic acids, notably gallic and proto-catechuic acids;