Mudarol, the chief resinol component of the root bark ofCalotropis gigantea, has been separated into two isomeric compounds by fractional crystallisation of the acetates and also by chromatographic adsorption analysis of the free alcohols. Giganteol which was first obtained from the stem bark is one of them and a new triterpene alcohol, isogiganteol is the other. The properties and reactions of the new resinol are described. Though giganteol and isogiganteol (C₃₀H₅₀O₂) have two oxygen atoms they form only monoacetates. They do not combine with dinitrophenyl-hydrazine.

The latex ofCalotropis gigantea contains caoutchouc to a small extent. 1.3%. The resinols are best separated from the coagulum by means of acetone. The mixture consists essentially of resinols having the formula C₃₀H₅₀O and by repeated fractional crystallisation a very small yield of α-calotropeol could be obtained. The toxic principle of the latex, gigantin, contains nitrogen and sulphur and resembles uscharin in several respects, but differs from it in composition and in its behaviour on hydrolysis.

Extraction of the fruits ofZanthoxylum acanthopodium has yielded a new crystalline component and it is named tambuletin. It seems to occur in the place of tambulin reported by earlier workers. It has the composition C₁₆H₁₂O₇ and is a monometyl ether. Experiments on methylation and demethylation prove that it is a monomethyl ether of herbacetin and its reactions suggest that the methoxyl group is in the 8-position.

Jack tree latex has the same composition as the fruit gum. Besides proteins and mineral substances, the two contain a high percentage of waxy matter. The less soluble portion (small amount) of the wax yields on saponification a non-steroid substance melting at 96-7° and having probable composition of C₃₀H₅₈O₂. The more soluble major fraction yields artostenone on saponification. Experiments indicate definitely that this ketone is not occurring free and that it is formed as a result of the saponification. Though artostenone does not have the capacity of forming enolesters, α-artostenone yields an enol-benzoate readily. Further α-artostenone and its enol-ester undergo conversion into artostenone under the conditions of saponification. Hence the conclusion is drawn that in the plant it is α-artostenone that occurs in the form of enol-wax-esters.

By partial ethylation tambuletin forms a definite triethyl-ether giving reactions for a free hydroxyl group in the 5-position. It undergoes oxidative demethylation thus confirming the location of the methyl-ether group in the 8-position. Complete ethylation yields O-tetraethyl-tambuletin which is found to be identical with 3∶5∶7∶4′-tetraethoxy-8-methoxy-flavone, synthesised from kaempferol using the method of nuclear oxidation.

α-Artostenone has been prepared directly from Jack fruit gum by saponification using sodium methoxide in cold methyl alcoholic solution. In preliminary tests α-artostenone enol-benzoate was found to yield α-artostenone under these conditions. Thus the conclusion that α-artostenone occurs in the plant in the form of enol-wax-esters is confirmed.

According to Bose and Bose² tambulin should be 3∶8∶4′-trimethyl-ether of herbacetin. A compound of this constitution has now been synthesised from 3∶4′-dimethyl-ether of kaempferol. Its properties differ markedly from those of tambulin. The constitution of the latter should therefore be considered as still unsettled. The nature of the synthetic substance has been confirmed by preparing its diethyl-ether and proving its identity with 3∶8∶4′-trimethyl-5∶7-diethyl-ether of herbacetin prepared by an independent method.

The synthesis of tambuletin has been effected. Kaempferol is first benzylated to the tribenzyl-ether which is subjected to oxidation with alkaline persulphate, partial methylation and debenzylation in succession.

Based on the evidences recorded in the past the constitution of tambulin is considered to be 7∶8∶4′-O-trimethyl-herbacetin. A substance of this constitution is synthesised by the partial demethylation of herbacetin-pentamethyl ether and is found to agree very closely with tambulin in properties. Hence its constitution is considered to have now been established.

The constitution suggested by Bose for gardenin (5-hydroxy-3∶6∶8∶3′∶4′∶5′-hexamethoxy-flavone) has been confirmed in the following manner.

In an earlier paper it was remarked that the colour reactions of norgardenin were rather extraordinary. Other flavonols belonging to the 5∶6∶8-hydroxy series and their methyl ethers have now been prepared using the fission ketone from methyl gardenin, and their properties studied. Their colour reactions resemble those of nor-gardenin and methyl gardenin closely. In general the hydroxy-flavonols of this series exhibit reactions with alkaline buffer solutions differing markedly from their isomers belonging to the 5∶7∶8- or 5∶6∶7- series thus emphasising the importance of the 7-hydroxyl for this purpose.

The observation of Bose and Nath regarding the fission of gardenin with alcoholic potash is confirmed. The formation of ω-methoxy-3∶6-dihydroxy-2∶5-quino-acetophenone (II) in this reaction constitutes an example of oxidative demethylation by means of alcoholic potash. The same compound can be obtained from methyl gardenin through the stages (III) and (IV). Analogous partial methyl ethers of flavones with a free 5-hydroxyl are resistant to this treatment.

A method of distinguishing between a flavone and a flavonol and characterising the latter is described. It consists in subjecting the ketonic fission product of the fully methylated anthoxanthin, representing the condensed benzene nucleus to the action of 40% aqueous hydrobromic acid, ω-Methoxy-ketones derived from flavonols yield coumaranones which could be converted into benzylidene derivatives. Simpler examples and more difficult cases such as gossypetol-tetramethyl-ether and calycopteretol pentamethyl-ether have been used for the investigation. The nature of the products has been proved by independent synthesis. The ketone obtained by the fission of methyl gardenin undergoes this reaction and hence supports the constitution of gardenin as a flavonol. Ortho-hydroxy-ketones which are unsubstituted in the ω-position do not yield any crystallisable product in this reaction.

The structure of 6-methoxy-4 ∶ 5 ∶ 7-trihydroxy-benzal-coumaranone was suggested by Saloojaet. al.³ for one of the forms of pedicinin. A substance of this constitution has now been synthesised by applying the two stage process of nuclear oxidation to an appropriate compound of the benzalcoumaranone series. The synthetic product differs markedly from pedicinin. Similar difference has been noticed earlier with the flavanone isomer, allo-pedicinin. It is concluded therefore that the two melting points noted for pedicinin are due to the existence of two crystal forms.

Two isomers of methyl pedicinin are synthesised and studied: (1) 4: 7-dihydroxy-5: 6-dimethoxy-benzal-coumaranone and (2) 5: 6-dimethoxy-4: 7-quino-benzyl-coumaranone. The first is made from 2-hydroxy-3: 4: 5: 6-tetramethoxy-chalkone by conversion into the corresponding benzal-coumaranone, oxidative demethylation to 4: 7-quinone and reduction to the quinol. The second synthesis condenses pentamethoxy-benzene with α-bromo-β-phenyl-propionyl chloride to yield tetramethoxy-benzyl-coumaranone and oxidises it with nitric acid to the quinone. Their properties are different from methyl pedicinin and they do not undergo conversion into it. It is therefore concluded that methyl pedicinin should be given only the quinone chalkone formula and that the alternative formulations are not valid. Further the possibility of reversible isomeric change between chalkones and benzylcoumaranones does not find experimental support.

Para oxidation in the side-phenyl nucleus has now been investigated using potassium persulphate and 3′-hydroxy-3:5:7:4′:5′-pentamethoxy flavone obtained conveniently from cannabiscitrin. The resulting quinol on methylation yields 3:5:7:3′:4′:5′:6′-heptamethoxy flavone and on demethylation 6′-hydroxy myricetin which is the first example of a flavone having four hydroxyl groups in the side-phenyl nucleus.

4:5:6-Trimethoxy-coumaranone is obtained from quercetagetol-tetramethyl ether by treatment with hydrobromic acid and methylation of the product. It is conveniently synthesised from 2:6-dimethoxy-quinol which undergoes Friedel and Craft’s reaction with chloracetyl chloride satisfactorily.