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

JOURNAL OF THE SOCIETY not encountered in ordinary prac- tice . . . The usual process for the manu- facture of technical chlorophyll con- sists in the extraction of suitable green vegetable matter, such as lucerne or nettles, with alcohol or acetone. Such an extract contains the chlorophylIs along with a com- plex mixture of carotenoids, phos- phatides, fatty esters, etc., and a proportion of water-soluble matter. This water-soluble matter can readily be separated and extracted ß if the residue, after removal of the extraction solvent, is dissolved in a suitable water-immiscible solvent. However, the resultant purified "chlorophyll" still consists of a gross mixture of substances that cannot readily be separated further, since their solubilities in most sol- vents are very similar. Also they are neutral and do not lend themselves to separation by chemical means which do not at the same time alter the chlorophylIs. Even during re- covery of the initial solvent used for extraction, some alteration of the chlorophylIs takes place. It has al- ready been noted that the magnesium is very readily removed from chloro- phyll by the action of acids. This change actually does take place to a greater or les•er extent during re- covery of the solvent, due to the action of natural acidic materials present in the extract. There is no. doubt that each manufacturer ap- plies his own methods, based on re- search and experience, to the solu- tion of these problems. No matter how successful such "know-how" 188 OF COSI•IETIC CHEMISTS may be, however, most commercial products consist of chlorophyll or its derivatives diluted with a much larger amount of other plant consti- tuents or their degradation products. Such commercial chlorophylIs are, in fact, plant extracts containing a fair concentration of chlorophyll, or more usually chlorophyll deriva- tives. Nevertheless, the chlorophyll in such preparations can and does undergo the changes that have been described for the pure material though matters are considerably complicated by the fact that chemi- cal treatment also causes changes in certain of the other substances pre- sent as impurities. OI!L-SOLUBLE CHLOROPHYLLS. Such materials are produced by methods similar to that which has just been outlined. They occur as soft extracts or fluids, and usually contain not more than about 15 per cent of chlo.rophyll or its derivatives. Since most of the magnesium is usually lost in processing, such products con- tain mainly phaeophytin. They nearly always contain quite a large amount of phosphorus, in the form of phosphatides or their degradation products, as well as carotenoids and numerous other natural constituents. When intended for medicinal or pharmaceutical use they are not usually treated with a copper salt to develop the colour. Nevertheless, since green vegetable matter often contains copper to the extent of about 20 p.p.m., such untreated chlorophylIs are liable to contain several hundred p.p.m. of copper.