Resins_1

Denston’s concise monographs are a pleasure to read and  deserve to be more widely read.

A solution of a resin in a volatile solvent, when painted on a smooth  surface should rapidly and completely dry to form a hard transparent film; to be  suitable for varnish the film should not darken with age or become impaired upon  exposure to light or moisture.

Formation of Resins.
In many instances resin in plants is formed in special passages or tubes  called resin ducts, which usually anastomose: thus a single incision may drain  the resin from a considerable area of the plant. The cells lining the duct  possess a layer (called the resinogenous layer) of slimy matter bounded by a  fine cuticle and, according to Tschirch, resin is secreted in this layer and  excreted through the cuticle into the resin duct. In some cases, e.g. copaiba,  numerous resin ducts are present. and although tapping is necessary. to drain  the ducts, the wound per se is in no way responsible for the production of  the resin, which is thus termed a normal or physiologically-produced  resin.

In other instances, e.g. turpentine, only a few resin ducts are normally  present, but following injury to the cambium the new (secondary) wood  subsequently formed contains a very large number of ducts, and the resin from  these is called wound, traumatic, or pathologically-produced resin. Resin may  continue to flow for a considerable period from wounding, or in some cases it  may be necessary to inflict wounds at frequent intervals. Further, invasion of  the wound by fungi and bacteria sometimes plays an important part in the  composition of the resin exuded. To illustrate, the simple wound resin of Styrax  Benzoin differs materially from the resin exuded after fungal invasion of the  wound.

Composition of Resins.
Resins are not single chemical compounds, but are usually mixtures of  substances of different and complex chemical characters.
The following are the three more important groups of compound present in  resins; 

1. Resin Esters.These consist mostly of resin alcohols  combined with aromatic acids, of which benzoic and cinnamic acids are of  frequent occurrence; other aromatic acids are less frequently found, e.g. ferulic acid (in asafetida). There are two principal kinds of resin  alcohols in combination with these acids.

(a) Resinols – These are colourless, and give a negative  reaction when tested with iron salts. The resin in benzoin consists principally  of the resinol, benzoresinol, combined with cinnamic and benzoic acids.

(b) Resinotannols – These are phenolic compounds, and give blue,  green or violet-coloured compounds with ferric chloride. They are usually named  from their source, e.g. the resinotannol in balsam of Tolu is called  toluresinotannol, and it occurs combined with benzoic and cinnamic acids; that  from Sumatra benzoin is called sumaresinotannol, and it is similarly combined. Like  other esters, the resin esters are saponified when boiled with alcoholic  solution of potassium hydroxide, and the previously combined acid obtained as a  water-soluble potassium salt. From the latter the aromatic acid (practically  insoluble inwater)  may be obtained by distillation of the reaction mixture (to remove the alcohol},  extraction of the residue with water , and acidification of the solution with a  mineral acid, whereupon the aromatic acid is precipitated.

2. Resin Acids.
These acids, also called resinolic acids, are of high molecular weight  and very complex. They usually occur free, and preponderate in some resins, e.g.  90 per cent or more of colophony (American) consists of the resin acid called  abietic acid.

3. Resenes.
The chemical nature of these compounds is unknown. They are very stable,  being unaffected by most chemical reagents or by exposure to moisture and  light-hence resins consisting principally of resenes yield good varnishes  provided the film is hard and therefore resistant to mechanical injury. The  resenes are usually named from their source, e.g. that of Sandarac is called  Sandaracoresene. The resene containing resins are, of course, those chiefly used  in the manufacture of varnishes. Sandarac is used in pharmacy for making pill  varnish.

Classification.
Various more or less unsatisfactory attempts have been made to classify  resins according to principal components; the following classification includes  the resins, gum-resins, and oleo-resins described in this book.

1.Resins consisting principally of Resin and other Esters,  together with free Aromatic Acids.
Resin, Resin or other Gum-Resin Esters Aromatic Acids or  Oleo-Resin

Benzoin (sumatra) {Benzoresinol and  Sumaresinotannol}Cinnamic Acid 11 % combined with cinnamic and benzoic acids 60%  Benzoic Acid 9%.

Asafetida. Asaresinotannol combined with ferulic  acid.

Balsam of Peru. Peruresinotannol combined with cinnamic and  benzoic acids 28%. Benzyl benzoate and cinnamate 58 – 70%.

Storax. Storesinol, free and combined with 35-40% Cinnamic  Acid 16-24% Storax Cinnamates of ethyl phenylpropyl and 25% cinnamyl alcohols  (average)

Balsam of Tolu.
Toluresinotannol combined with cininamic and benzoic acids 80% Cinnamic  Acid 12%
Benzyl benzoate and cinnamate 7.5% Benzoic Acid 8%.

2. Resins consisting principally of Resin Acids.
Resin, Oleo-Resin or Gum-Resin and Resin Acids : Colophony: Copaiba,  Myrrh :

3. Glyco-Resins.
This important and complex group comprises the glycosidal resins, which  are so-called because when they are boiled with mineral acids hydrolysis takes  place, with production of a sugar (usually dextrose) and a complex resin acid  and simpler acids. Jalap resin and Ipomoea resin are examples of glyco-resins.

CHEMICAL EXAMINATION OF RESINS.
The acid value, saponification value, and iodine value may be determined  on lines similar to those for fixed oils and fats. The saponification and iodine  values are rarely criteria because they differ widely in samples of genuine  drug. The acid value is, however, of some importance, particularly in examining  resins for varnish making, because these often consist of a mixture of resin  acids and resenes in fairly constant proportion. In such cases determination of  the acid value serves to detect adulteration with cheaper resins containing more  free acid (e.g. colophony) or less.

Benzoin, balsam of Tolu and storax are officially required to contain a  defined proportion of balsamic acids (benzoic and cinnamic), and balsam of Peru  50.0-70.0 per cent of ester (benzyl cinnamate and benzoate). Specific analyses  for these are described in the Pharmacopeia. In many instances, the Pharmacopeia  prescribes solubility tests to guard against adulteration or to limit the  proportion of impurities. For example, not more than 24.0 per cent of benzoin  should be insoluble in 90 per cent alcohol, indicating absence of an undue amount of wood debris,  etc.

Martindales 24th Ed. BENZOIN and other  RESINS.
Benzoin (B.P.) Sumatra Benzoin; Gum Benzoin; Gum Benjamin;  Benzoe.
Dose: 0.6 to 2 g. (10 to 30 grains). A balsamic resin from  the incised stem of Styrax benzoin and of S. paralleloneurum (Styracacere) and  containing various esters of benzoic and cinnamic acids together with the free  acids. (Note. The B.P. 1948 allowed both Sumatra benzoin and Siam  benzoin).

Foreign Pharmacopeias: In Chin., Cz., Egyp., Hung., Ind.,  Jap., Mex., and U.S., all of which allow both Siam benzoin and Sumatra benzoin.  In Belg., Chit., Dan., Fr.,Ger., Jug., Nor., Span., Swed., and Swiss, all of  which specify Siam benzoin only.

Hard brittle masses of whitish tears embedded in a greyish-brown to  reddish-brown translucent matrix; it has an agreeable balsamic odour and a  slightly acrid taste. Store in a cool place,
Uses. Benzoin acts as a reflex expectorant but it is seldom  given internally.

Siam Benzoin (BPC) A balsamic resin from the incised stem of  Styrax tonkinensis (Styracacere) and containing about 68% of crystalline coniferyl benzoate together with  free benzoic acid, ( +) siaresinolic acid, vanillin, and a small amount of  cinnamyl benzoate.

Foreign Pharmacopeias: In many pharmacopeias. under the  title Benzoin (see above under Benzoin).

In flattened irregular tears or ill irregular masses consisting of tears  embedded in a brownish-red, translucent, resinous matrix. The tears are usually  about 1 to 2 cm. wide and about 0.5 to 0.7 cm. thick; externally they are  covered with a brownish-red varnish-like layer of resin, but the  freshly fractured surface is milky white. Siam benzoin resembles Sumatra benzoin  in odour and taste. Store in a cool place.
Uses. It is used to  inhibit the development of rancidity in fats, its action being apparently due to  the presence of coniferyl benzoate. It is a more efficient preservative than  Sumatra benzoin, and is used in the preparation of Benzoinated Lard.

Compound Benzoin Tincture (U.S.P) Prepared by macerating  benzoin (Sumatra or Siam) 10 g., aloes 2 g., storax 8 g., and balsam of tolu 4  g., with alcohol to 100 mI.

Compound Tincture or Benzoin (B.P.) Tinct. Benzoin. Co.  Friars’ Balsam; Traumatic Balsam. Prepared by maceration from Sumatra benzoin  (10%), prepared storax, aloes, balsam of tolu, and alcohol (90%).
Dose: 2  to 4 ml. (30 to 60 minims). Uses. It is occasionally used internally in  chronic bronchitis; 60 minims to a pint of hot water is employed as an  inhalation in bronchitis and acute laryngitis. Undiluted it is used as an  antiseptic and styptic to small cuts. Mixtures require the addition of equal  parts of mucilages of acacia and tragacanth to suspend the resins, the total  amount of mucilage being one-eighth of the volume of the mixture.

Inhalation or Benzoin (B.P.C.). Vap. Benzoin. (B.N.F.) Prepared by macerating Sumatra benzoin 45 gr. and prepared storax 30 gr. with alcohol to 1 fI. oz.

Lot. Benzoin. (B.P.C; 1934) Lotion of Benzoin; Lait  Virginal. Tincture of benzoin 2.5 mI., rose water to 100 ml. Useful as a face  lotion in urticaria and other irritable skin conditions.

Neb. Benzoin. Co. (B.P.C. 1934). Compound Benzoin Spray.  Pumilio pine oil 1.5 ml., eucalyptus oil 3 ml., cassia oil 1.5 ml., mentholl g.,  glycerin 50 ml., tincture of benzoin to 100 ml.

Tincture or Benzoin (B.P.C.) Tinct. Benzoin. ; Simple  Tincture of Benzoin. Sumatra benzoin 1 in 10, prepared by maceration with  alcohol (90%). Dose: 2 to 4 ml. (30 to 60 minims).

Similar tinctures in Belg. P., Chin. P., Cz. P., Dan. P.,  Fr. P, Jug. P., Span. P., Swiss P. and U.S..P. which are all l in 5.

Balsam of Tolu (B.P.) BalsamumTolutanum.
Foreign Pharmacopeias: In Belg., Chil., Dan., Egyp., Fr., Ger., Ind.,  Jap., Jug.,Mex., Nor., Span., Swed., Swiss, and U.S.

A balsam obtained by incision from the trunk of Myroxylon balsamum (= M.  toluiferum) (Leguminosae). It is a soft, tenacious, brownish-yellow or brown  resinous solid when fresh, but it subsequently becomes harder and finally  brittle. It has an aromatic odour and taste. Almost insoluble in water  and light petroleum; soluble in alcohol, benzene, chloroform, ether, and  glacial acetic acid; partly soluble in solutions of caustic alkalis; partly soluble in carbon disulphide, the soluble portion consisting chiefly of cinnamic acid.
Uses. It has a very mild  antiseptic action but is mainly used as a reflex expectorant. The syrup is a  common ingredient of children’s cough mixtures.

[P1] Compound Linctus of Tolu for Infants (B.P.C.). Linct.Tolu. Co. pro Inf. (B.N.F.). Citric acid 112 gr., syrup of wild cherry 20  m., glycerin 15 m., syrup of tolu to 60 m. Dose: 2 to 4 ml. (30 to 60  minims)

Solution of Tolu (B.P.C.). Liq. Tolu. Prepared from balsam  of tolu 10 g., alcohol (90%) 30 ml., sucrose 50 g., and water to 100 ml. One  volume with 7 of syrup yields a preparation more aromatic than syrup of  tolu.

Syrup of Tolu(B.P.). Syr. Tolu. Prepared from balsam of tolu  2.5 g., sucrose 66g. and water to 100 g.
Dose: 2 to 8 ml. (30 to 120  minims).

Tincture of Tolu (B.P.C.) Tinct. Tolu.; Tolu Balsam  Tincture. 1 in 10 of alcohol (90%). Several pharmacopeias (Belg., Chil., Dan.,  Fr., Mex., Swed., and U.S.) specify 1 in 5. In mixtures the resin must be  suspended with mucilage.
Dose: 2 to 4 ml. (30 to 60 minims).

Tolu Balsam Syrup (U.S.P.) Syrup of Tolu. Tolu balsam  tincture 5 ml., triturated with magnesium carbonate 1 g., sucrose 6 g., water 43  ml., and filtered; sucrose 76 g. dissolved in the filtrate, strained, and  diluted to 100 ml.

Tolu Basis for Lozenges (B.P.C.) For 100 lozenges: tincture  of tolu 2 ml., sucrose 100 g., acacia 7g., water q.s.

Vernix Tolutana (Dan. P.) Tolu Varnish. Balsam of tolu 16.5  g. dehydrated alcohol 25 g. ether 58.5g.

Ammoniacum (B.P.C. 1949).
Dose: 0.3 to 1 g. (5 to 15 grains).
Foreign Pharmacopeias: In Belg., Fr., GeT., Nor., Span., and  Swiss.
A gum-resin from the flowering and fruiting stem of Dorema ammoniacum and  possibly other species of Dorema (Umbelliferae). Pale yellow tears or nodular  masses with characteristic odour and acrid taste.
Uses. It has been used  to facilitate expectoration in chronic bronchitis with viscid secretion.

Note: Ammoniacum is dilute solution of ammonia in Chil.P.  and strong solution of ammonia in Span.P  

Asafetida (B;P.C. 1949) Gum Asafetida; Devil’s Dung;  Asant.
Dose: 0-3 to 1 g. (5 to 15 grains). Foreign Pharmacopeias:  In Belg., Egyp., Ger., Ind., Span., and Swiss. Also in U.S.N.F.

An oleo-gum-resin obtained from the living rhizome and root of Ferula  assafoetida, F. foetida,  F. rubricaulis, and probably other species of Ferula (Umbelliferae). It  is in the form of greyish-white or yellow tears with a garlic-like odour and  bitter acrid taste. Store in a cool place.
Uses. Asafetida has a carminative action and has been  employed in intestinal flatulence, sometimes as an enema. It also has an  expectorant action and has been used in bronchitis. It was at one time widely used for its supposed effect in nervous disorders, but any effect it might have in these conditions is attributed entirely to the psychological response to the  objectionable odour and taste.

Asafetida Pills (U.S.N.F.) Each contains asafetida 200 mg. and hard soap 60 mg. Usual dose: 2 pills.

Enema Asafoetidae (B.P.C. 1934) Tincture of asafetida 6 to  12% v/v in mucilage of starch.
Dose: 120 ml. (4f1. oz.).

Mist. Asafoet. Co. (Cape Hosp.). Mist. Diabolica. Tincture  of asafetida 15 m., cod-liver nil 15 m., solution of potassium hydroxide 10 m.,  infusion of quassia to ? .f1. oz.