JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS " NH HN CH L1, - C• CHiC H• COO CarUso Phceophytin a (R = CHa) and Phceophytin b (R = CHO) STRUCTURAL FORMULA III R 186 Chlorophyllin a (R -- CH) and Chlorophyllin b (R = CHO) STRUCTURAL FORMULA IV

CHLOROPHYLL chlorophyll. The copper compound is typical of these derivatives and is probably the most important. Copper chlorophyll, or as it is more correctly termed--copper phaeophy- tin -- is much faster to light than true chlorophyll and is also, unlike the latter, very stable to the action of acids. When true chlorophyll is treated with alkalis, its behaviour is quite different [rom that resulting from acid treatment, in that the magnesi- um is not removed. Equally, if the magnesium has previously been re- placed by ano,ther metal such as copper, this metal is not removed. Instead, the ester groups are at- tacked and hydrolysed. The phytyl group is much more readily split off, the methyl ester being relatively re- sistant to hydrolysis. However, under appropriate conditions, it is fairly simple to split off both alco-- holic residues with simultaneous formation of a salt of the dicarboxy- lic acid, chlorophyllin (IV). This, apart from the loss of the phytyl and methyl residues, has the same structure as the original chlorophyll. The sodium and po,tassium salts of this acid are soluble in water and such salts constitute the active con- stituents of the so-called water- soluble chlorophylis. When chlorophyll is hydrolysed with alkali under more vigorous conditions, a further change occurs. Besides losing the phytyl and methyl residues, the lsocyclic ring is opened with the production of a third car- boxylic grouping. This tri-carboxylic acid is known as isochlorophyllin (V). All that has so far been said about the chemistry of chlorophyll has re- ferred to the pure substance or its pure metallic derivatives. However, such materials are so. difficult to isolate in the pure state that they are • H f .... CHICcoo ..... c[t2 -- CH isoChlorophyllin a (R = CH:,) and isoChlorophyllin b (R = CHO) STRUCTURAL FORI•IDLA V 187